Data from the

NATIONAL HEALTH SURVEY

HematocritValues

OfYouths12=17Years

United States

Hematocrit values are presented and discussed by age, sex, race, and socioeconomic level of youths 12-17 years of age in the UnitedStates, 1966-70.

DHEW Publication No. (HRA) 75-1628

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE

Public Health Service -

Health Resources Administration

National Center for Health Statistics

Series 11

Number 146

Rockville, Md. December 1974
Series 11 reports present findings from the National Health Examination Survey, which

obtains data through direct examination, tests, and measurements of samples of the U.S.

population. Reports 1 through 38 relate to the adult program, Cycle I of the Health

Examination Survey. The present report is one of a number of reports of findings from the

children and youth programs, Cycles II and III of the HeaIth Examination Survey. These

latter reports from Cycles II and HI are being published in Series 11 but are numbered

consecutively beginning with 101. It is hoped this will guide users to the data in which they

are interested.

Library of Congress Cataloging in Publication Data

Heald, Felix.

Hematocrit values of youths 12-17 years, United States.

(National Center for Health Statistics. Data from the National Health Survey, series 11,

no. 146) (DHEW publication No. (HRA) 75-1628)

Supt. of Dots. no.: HE 20.6209:11/146.

1. Hematocrit. 2. Youth–Health and hygiene. 3. United States–Statistics, Medicul. I.

Levy, Paul S., joint author. II. Hamill, Peter V. V., joint author. 111, Rowland, hlichael, joint

author. IV. Title. V. Series: United States. National Center for Health Statistics. Vital and

health statistics. Series 11: Data from the National Health Survey, Data from the health

examination survey, no. 146. VI. Series: United States, Dept. of Health, Education, and

Welfare. DHEW publication no. (HRA) 75-1628. [DNLhl: 1. Hematocrit–In adolescence.

W2A N14vk ser. 11 no. 146]

RA407.3.A347 no. 146 [RB45] 312’.0973s

ISBN 0-8406-0025-9 [312’.31’500973] 74-12434

For sale by the Superintendent of Documents, U.S. Qovernmsnt Prfnting Office,Waehfngton, D.C. Z134GZ- Pric8 $1
NATIONAL CENTER FOR HEALTH STATISTICS

EDWARD B, PERRIN, Ph. D., Director

PHILIP S. LAWRENCE, SC.D., .Depttjv Director

JACOB J. FELDMAN, Ph. D., Acting Associate Director for Analysis

GAIL F. FISHER, Associate Director for the Cooperatzlq Health Statistics System

ELIJAH L. WHITE, Associate Director-for Data Systems

IWAO M. MORIYAMA, Ph. D., Associate Direct&-for International Statistics

EDWARD E. MINTY, Associate Director for Management

ROBERT A. ISRAEL, Associate Director for Operations

QUENTIN R. REMEIN, Associate Director for Program lleve~oprnent

PAUL E. LEAVERTON, Ph. D., Acting Associa;e Director for Research

ALICE HAYWOOD, .Inforrnation Officer

DIVISION OF HEALTH EXAMINATION STATISTICS

ARTHUR J. McDOWELL, Director

JEAN-PIERRE HABICHT, M.D., SC.D., Specicd Assistant to the Director

PETER V. V. HAMILL, M.D., Medical Advisor

JEAN ROBERTS, Chie~ Medical Statistics Branch

ROBERT MURPHY, Chief Survey Pkming and Devei’opment Branch

COOPERATION OF THE BUREAU OF THE CENSUS

In accordance with specifications established by the National Health

Survey, the Bureau of the Census, under a contractual agreement, participated in the design and selection of the sample, and carried out the first stage

of the field interviewing and certain parts of the statistical processing.

Vital and Health Statistics-Series1l-No. 146

DH EW Publication No. (HRA) 75-1628

Library of Congress Catalog Card Number 74-12434

r
CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Blood Specimen and Microhematocrit . . . . . . . . . . . . . . . . . . . .

Race . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SexandAge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GeographicRegion,Sex,andAge . . . . . . . . . . . . . . . . . . . . . .

Race,Sex,andAge . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AnnualFamilyIncome,Sex,andAge . . . . . . . . . . . . . . . . . . . .

EducationofParent,Sex,andAge . . . . . . . . . . . . . . . . . . . . .

Annual Family Income, Education of Parent, Race, Sex, and Age . . . . .

.-.

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AgeandSex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Race . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IncomeandEducation . . . . . . . . . . . . . . . . . . . . . . . . . . .

Interaction Between Race and Socioeconomic Status . . . . . . . . . . . .

GeneraI Comparability With Other Studies . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ListofDetailedTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

,4ppendixI. Statistical Notes . . . . . . . . . . . . . . . . . . . . . . . . .

TheSurveyDesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SomeNotesonResponseRates . . . . . . . . . . . . . . . . . . . . . . .

ParameterandVarianceEstimates . . . . . . . . . . . . . . . . . . . . . .

Standards of Reliability and Precision . . . . . . . . . . . . . . . . . . . .

Imputation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AppendixII. Demographic Variables . . . . . . . . . . . . . . . . . . . . .

Appendix III. Techniques ofMeasurement and Quality Control . . . . . . .

Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MonitoringSystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

hflethods of Taking Replicate Measurements . . . . . . . . . . . . . . . . .

Results of the Replicate Studies for Hematocrit . . . . . . . . . . . . . . .

1

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3

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Ill
SYMBOLS

Datanot available --------------------------------------- ---

Category not applicable ------------------------------ . . .

Quantity zero --------------------------------------------- -

Quantity morethan Obutless than0.05---- 0.0
HEMATOCRIT VALUES OF

Felix Heald, M. D., Paul S. Levy, SC.D., Peter V. V.

YOUTHS 12-17 YEARS

Hamill, M.D., M.P.H., and Michael Rowlanda

INTRODUCTION

This report of hematocrit values as determined from blood samples of youths 12-17

years of age in the United States is one of a

series of reports presenting findings from Cycle

III of the Health Examination Survey. The

means and selected percentiles of the hematocrit

values are examined here by sex, age, race,

family income, education, and geographic region

of the United States. As described in a detailed

report of its general plan and operation, 1 the

Health Examination Survey (HES) is conducted

in a succession of cycles.

Cycle I of the HES, conducted from 1959 to

1962, obtained information on the prevalence of

certain chronic diseases and on the distribution

of a number of anthropometric and sensory

characteristics in the civilian, noninstitutionalized population of the continental United

States, aged 18-79 years. The detailed plan of

Cycle I is described in a previous report,2 and

aProfcssor of Pediatrics, Director, Division of Adolescent

Medicine, University of Maryland, School of Medicine; Associate

Professor of Biometry, University of Illinois, School of Public

Healtti Medical Adviser, Chfldren and Youth Programs, Division

of Heahh Examination Statistics; Analytical Statistician, Division of Health Examination Statistics, respectively.

most of the results are published in other reports

of Series 11 in Vital and Health Statistics. -

Cycle II of the HES, conducted from July

1963 to December 1965, involved selection and

examination of a probability sample of noninstitutionalized U.S. children, 6-11 years. This

program succeeded in examining 96 percent of

the 7,417 children selected for the sample. The

examination had two focuses: (1) factors related

to healthy growth and development as determined by a physician, a nurse, a dentist, and a

psychologist and (2) a variety of somatic and

physiologic measurements performed by specially trained technicians. The detaiIed plan and

operation of Cycle II and the response results

are described in Vital and Health Statistics,

Series l-Number 5.3

HES Cycle III, conducted from March 1966

to March 1970, was essentially an agewise

extension of Cycle II into adolescence. As

described in detail in “Plan and Operation of a

Health Examination Survey of U.S. Youths,

12-17 Years of Age,”4 Cycle III was more

similar to Cycle II than to Cycle I not only in

form, content, and style but also in having its

major emphasis on factors of “normal” growth

and development rather than on chronic diseases. These analyses on “normal” growth and

1
development of adolescents have been well

underway since 1970, and some of the results

from the battery of body measurements have

already been published.5 -7

This report, which presents the first of the

findings from the sample of blood drawn from

each youth, is closer in content to Cycle I than

to Cycle II, because no blood specimen was obtained from the children in Cycle II. One was

obtained from the adults in Cycle I and among

the determinations made was the hematocrit. On

the other hand, the present report, like those of

Cycle II, primarily deals with factors relating to

growth and development. As will be shown, there

was a marked “growth” in the erythrocyte

volume for adolescent boys, while that for adolescent girls remained essentially stationary.

In this report, the means and selected percentiles of the hematocrit values are examined by

sex, age, race, family income, education of

parent, and geographic region of the United

States.

METHOD

At each of 40 preselected locations (see

appendix I for sample design) throughout the

United States, the youths were brought to the

centrally located mobile examination center for

an examination that lasted about 3% hours. Six

youths were examined in the morning and six in

the afternoon. Except during vacations, they

were transported to and from school and/or

home.

When the youths entered the examination

center, their oral temperatures were taken, and a

cursory screening for acute illness was made; if

illness was detected, the youth was sent home

and reexamined later. The examinees changed

into gymnasium-type shorts; cotton sweat socks;

a terry-cloth robe; and, for the girls, a light,

sleeveless topper. All six then proceeded to

different stages of the examination, each one

following a different route. The 3Yz-hour examination was divided into six 35-minute time

periods, each consisting of one or more detailed

examinations at a designated station. At the end

of each period, the youths rotated to another

station so that at the end of 31% hours each

youth had been given essentially the same

examinations by the same examiners but in a

different sequence. Four of these examination

time periods were allocated to examinations by

a pediatrician, a dentist, and a psychologist ,b

and the other two were allocated to a group of

examinations performed by highly trained technicians. This last group of examinations consisted of X-rays of the chest and hand-wrist,

hearing and vision tests, measures of respiratory

function, a 12-lead electrocardiogram, a submaximal exercise tolerance test on a treadmill

with chest leads to a continuous electrocardiogram, a battery of body measurements,

grip strength, examination of blood and (on girls

only) urine cultures for bacteria, and a privately

administered health behavior and attitude questionnaire.

Blood Specimen and Microhematocrit

The development of the technique used by

HES for obtaining and processing the blood

specimen is described in appendix HI. When the

venipuncture needle was withdrawn from the

arm, the tubing was partially drained, and two

micro capillary tubes were two-thirds filled with

the residual blood in the tubing. The ends were

fjlled with Sealease and the tubes placed into a

special autocrit carrying tray. The tray was

centrifuged at 12,500 r.p.m. for 5 minutes, and

a reading was taken on each tube directly on the

tray. Care was taken to read immediately after

centrifugation—the tubes were not allowed to sit

for long periods of time. The reading was

expressed as the percentage that the volume of

the packed red blood cells comprised of the

initial whole blood specimen in the microcapillary tube.

The microhematocrit was the only laboratory

determination performed in the examination

trailers on the blood specimen. The bulk of the

blood samples, after preliminary preparation in

the trailer’s laboratory, were properly separated

into their various sub samples and packed into

specially devised Styrofoam containers for shipment via air freight to either the Immunogenetics Laboratory of The Johns Hopkins UniverbThe entire examination by the psychologists consisted of

two consecutive time periods (70 minutes). Two psychologists

performed identical examinations simultaneously at separate

stations.

2
sity, Baltimore, Md., or the Center for Disease

Control (PHS), Atlanta, Ga.

Race

Race was recorded as “white,” “Negro,” and

“other races”c (see appendix II). In Cycle III,

the white youths constituted 84.74 percent of

the tokd, the Negro youths 14.76 percent, and

youths of other races only 0.50 percent. In

Cycle II, white chikiren constituted 85.69 percent of the examined subjects and Negro children, 13.86 percent. (The differential response

rate by age, sex, and race is analyzed and

discussed in appendix L The increased proportion of Negro subjects in Cycle III was due to

their better response rate–the overall Negro

response rate was 96.6 percent and the overall

white response rate was 89.1 percent. ) As in

Cycle II, because so few youths of “other races”

were part of the sample, data for them have not

been analyzed as a separate category. Whenever

dtita are analyzed independent of a classification

by race, however, data for these youths are

included.

tions. Percentage distribution of hematocrits is

given for these youths by age and sex in table 2.

In male youths, mean hematocrit levels increased consistently with age, from a low of

40.5 ml percent for 1Z-year-olds to a high of

45.8 ml percent for 17-year-olds (table 1 and

fi~re 1). This represents an estimated increase

of 5.3 ml percent or 1.06 ml percent per year

over the 6 years of adolescence. In females,

however, no such increase with age was seen; the

mean hematocrit levek remained within the

40.3-40.7 ml percent range throughout adolescence (table 1 and figure 1). For each of the six

age groups, mean hematocrit levels were higher

in males than in females. Differences between

the mean hematocrit levels of male and female

youths increased consistently with age, from 0.2

ml percent for 12-year-olds to 5.2 ml percent for

17-year-oIds.

The increase in mean hematocrit levels with

age for male youths is also seen when the data

are examined by percentiles (table 1). The 5th

percentile for male youths increased consistently

with age, from a low of 36.0 percent for

RESULTS

Sex and Age

The estimated number of youths falling into

mch of 16 groups according to hematocrit levels

is shown by age and sex in table 1 along with

sckcted percentiles, mean hematocrit levels, and

sttindard deviations of the hematocrit distribucThe same classification scheme as used in the 1960 census

was employed here. As deseribed in the reviously mentioned

1’ rcpcwt on the operation of HES Cycle III, this information was

obtained at the initiaI household interview by the Bureau of the

Census ficldworker. The accuracy of the information was

chcckcd at the subsequent home visit by the highly experienced

rcprmxmtativc from HES and again at the examination in the

tr.silcr. A final record check by birth certificate turned up only

scvtm inconsistencies, and these were mostly pertaining to the

catc~ory “other races.” Hence, the possible extent of misclassific~tion of the variable race, as described, is so minimal that it

could have no effect on the data anatyzed in tbk report.

Howcw,r, when comparing the present HES findings with those of

other variously defined racial groupings in the world, the degrees

of genetic admixture, as first discussed by Herskowitz8 in 1928

and Iatcr by Glass and LI,- “ q by Roberts,10~11 and by Reed, 12

should bc t~en into consideration.

12 13 14 15 16 17

AGE IN YEARS

Figure 1. Mean hematocrit levels for youths aged 12-17 years,

by age and sex: United States, 1966-70.

3
●

12-year-olds to a high of 41.2 ml percent for

17-year-olds. No such increase with age in the

5th percentile was seen for females. Values of

this percentile for females remained within the

35.8 -37.0 ml percent range throughout the 6

years of adolescence. The median, or 50th

percentile, of the hematocrit distribution in

male and female youths at each age showed the

same variations with age and sex as the mean. At

the upper end of the distribution, the 95th

percentile for male youths increased with age

from 45.2 ml percent in 12-year-olds to 50.3 ml

percent in 17-year-olds. No such increase with

age was seen in females.

In an attempt to gain further insight into the

nature of the increase in hematocrit levels for

male youths, data were amdyzed for 6-month

age groups from 12 to 18 years (table 3). Those

youths who were between 12 years and 12!4

years were included in the 12-year age group;

those between 12% and 12% years of age, in the

12%-year age group; those between 12% and

13?4, the 13-year age group; and so forth. Those

male youths 173A years and over were included

in the 18-year age group. There was an irregularity in the classification at the two extreme age

groups because only youths over 12 years and

under 18 years of age were eligible to participate

in the examination.

Mean hematocrit levels in male youths for

6-month age groups increased consistently and

rather uniformly with age, from a low of 40.-~

ml percent for 12-year-old males to a high of

46.0 ml percent in 18-year-old males (table 3).

An examination of successive differences between these means shows that the largest difference (0.8 ml percent) occurred between 14 and

14Y2 years of age. Differences of 0.6 ml percent

or more, however, occurred between 13 and

13% years (0.6 ml percent), 14% and 15 years

(0.6 ml percent), and 15 and 15% years (0.7 ml

percent). The smallest differences between

means occurred at the two extreme age groups

(which have irregular age compositions), where

the difference in mean hematocrit between 12-

and 12?4-year-olds was 0.1 ml percent, and that

between 17?4+ and 18-year-olds was 0.2 ml

percent.

In describing the shape of the distribution of

hematocrits, we have used three summary statistics–namely, the distance between the mean and

the median, the distance between the 5th

percentile and the median, and the distance

between the 95th percentile and the median

(table 4). In male youths, the median at each age

was slightly higher than the mean, but the

distance from the 5th percentile to the median

was approximately the same as that from the

median to the 95th percentile. Thus, the distribution for males at each age group was fairly

symmetrical.

For females aged 12, 16, and 17 years, the

mean and median ht -natocrits were always

within 0.1 ml percent of each other; and the

distance between the 5th percentile and median

was nearly the same as that between the median

and 95th percentiles, indicating symmetrical

distributions. On the other hand, although the

means and medians for females aged 13, 14, and

15 years were also virtually identical, the distance between the 95th and 50th percentiles was

greater than the dktance between the 5th and

50th percentiles by 1.0 ml percent or more.

Since the means and medians coincided, this

indicates that the lower 5-percent tail of the

distribution is longer than the upper 5-percent

tail, which, in turn, implies the presence of some

very low hematocrit levels for 13-, 14-, and

15-year-old females.

Geographic Region, Sax, and Age

Mean hematocrits and standard

mean hematocrits are shown in

errors of the

table 5 by

geographic region, sex, and age; and the number

of sampIe persons are shown in tabte 6 by the

same variables. Within each geographic region,

mean hematocrit increased with age in males but

not in females, a finding consistent with the

pattern discussed previously for the United

States as a whole. The findings show no evidence

of differences among regions with respect to

mean hematocrit levels.

Race, Sex, and Age

Findings by race, sex, and age are shown in

tables 7 through 11, and in figures 2 and 3.

The increase with age in mean hematocrit

found for male youths in the United States as a

whole was also found for Negro and white males
z

50

45

40 I

A.

/,

/

95th percentile white females

-” 95th percentile Negro females

4 50th percentile white females

.

--- +.. -b.--- - 50th percentile Negro females

-----

● ● 5th percentile white females * % \ .6.

-“ .

-. -- 5th percentile Negro females --0-

35 ““

30- -

0

12 13 14 15 16 1“7

AGE IN YEARS

Flgure2. Median, 5th, and95th percentiles of thehematocrit distribution ofwhite and Negro females by age: United States, 1966-70.

50-

45- -

40- “

35 “-

*-

*

----

95th percentile white males

95th percentile Negro males

50th percentile white males

50th percentile Negro males

5th percentile white males

5th percentile Negro males

01 1 I I t m

12 13 14 15 16 17

AGE IN YEARS

Figure3, Median, 5th, and 95th percentiles of thehematocrit distribution of white and Negro males byage:United States, 1966-70.

5
separately (table 7). Mean hematocrit levels

increased in white males, from a low of 40.6 ml

percent for 1Z-year-oIds to a high of 45.8 ml

percent for 17-year-olds. In Negro males, mean

hematocrit levels increased consistently with age

from 39.6 ml percent for 1Z-year-oIds to 45.7

ml percent for 17-year-olds. At each age, the

mean hematocrit for Negro males was lower

than that for white males of the same age.

In white female youths, there was no increase

with age in mean hematocrit, with mean levels

fluctuating between 40.4 and 40.9 ml percent.

In Negro females, mean hematocrit levels were

lower in the 16- and 17-year-olds than in the

13-, 14-, and 15-year-old youths. At each age,

Negro females had lower mean hematocrit IeveIs

than white females, with the differences between races being very large (2.4 ml percent) for

16- and 17-year-old girls (table 7).

Selected percentiles of hematocrit levels are

shown for white and Negro youths in tables 10

and 11 and figures 2 and 3. The differences in

hematocrit levels between white and Negro

youths at the 5th, 50th, and 95th percentiles are

shown in table 8.

Differences between white and Negro males

were primarily at the lower end of the distribution (fi~re 3 and table 8). The 5th percentile

for white males was higher at each age than the

corresponding percentile for Negro males, with

these differences averaging 1.25 ml percent over

all ages. At the middle of the distribution,

differences between Negro and white males were

much smaller, with the median for white males

averaging 0.5 ml percent higher than that for

Negro males. In sharp contrast, at the upper end

of the distribution, there were no consistent

differences between white and Negro males at

the 95th percentile.

The hematocrit distribution for Negro males

had more variability associated with it than that

for white males (tables 10 and 11). The standard

deviation of the hematocrit distribution was

greater at each age for Negro males than for

white males, as was the distance between the

95th and 5th percentiles. If one distribution has

a lower median and greater variability y than

another, one would expect the differences between the two to be most striking at the lower

end of the distribution, w!~ich is exactly what

was observed in the hematocrit distributions of

white and Negro males.

Similar patterns appear when the differences

between the hematocrit distributions of white

and Negro females are analyzed (tables 8, 10,

and 11 and figure 2), except that the differences

were more apparent for females and they were

most striking for the older females (15-, 16-, and

17-year-olds). The 5th percentile for white

females averaged 3.0 ml percent higher than that

for Negro femzdes, with 16-year-oId white females having a 5th percentile that was 4.4 ml

percent higher than their Negro counterparts

(figure 2).

The median of white females was higher at

each age than that of Negro females, and the

difference was highest at the two oldest ages

(2.4 ml percent for 16-year-olds and 2.0 ml

percent for 17-year-oIds). At the upper end, the

95th percentile for white females was higher

than that for Negro females at all ages except 13

years. Again, as in males, differences between

Negro and white females were largest at the

lower end of the distribution, and smallest at the

upper end.

In all but 1Z-year-oIds, the standard deviation

of the hematocrit distribution was higher for

Negro females than for white females (tables 10

and 11).

Another way of lo~king at differences in

hematocrit levels by race is shown in table 12, in

which the percentage of persons with hematocrit

levels below three cutoff point s–i.e., 35.0 ml

percent, 37.0 ml percent, and 39.0 ml percent–

is shown by race, age, and sex. For both males

and females at each age group, the percentage of

Negroes having hematocrit levels below each of

these cutoff points was much greater than the

corresponding percentage of whites.

Annual Family Income, Sex, and Age

Mean hematocrit levels are given for maIe and

female youths by annuzd family income in table

13. A small but clear increase in mean hemat ocrit occurred with increase in annual family

income for both male and female youths at each

age group. Hematocrit levels of males in families

with annual incomes of $10,000 or more averaged (over all ages) 0.67 ml percent higher than

those of males in families with annual incomes

of less than $3,000, while the level of females in

families with annual incomes of $10,000 or

more averaged 1.08 ml percent higher than those

6
of females whose families had annual incomes of increase in mean hematocrit was found

less than $3,000 (figure 4). Table 14 shows the

10th, 50th, and 90th percentiles of the hematocrit distribution by age and sex for those in

farnilics with annual incomes less than $4,000

and for those in families with annual incomes of

$10,000 or more. Differences between youths

~,h(osc fanl~ies had ~nu~ incomes of $10,000”

or more and those whose families had annual

incomes less than $4,000 were generally greater

at the 10th percentile than at the median and

90th percentiles.

Education of Parent, Sex, and Age

Mean hematocrit levels by education of parent, SCX, and age are shown in table 15. An

L

with

increase in education of parent. Over all ages,

those male youths whose parents had 13 years

of education or more had mean hematocrit

levels approximately 0.82 ml percent higher

than those males whose parents had less than 8

years of education, while those females whose

parents had 13 years of education or more had

mean hematocrit levels approximately 1.13 n-d

percent higher than those females whose parents

had less than 8 years of education (figure 5).

Annual Family Incomer Education of Parent,

Race, Sex, and Age

Mean hematocrit levels are given by annual

family income, sex, and age (tables 16 and 17)

Males, annual family income less than $3,000

------ Males, annual family income $10,000 or more

--------- Females, annual family income less than $3,000

47 T

-------- Females, annual family income $10,000 or more

A

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z

41- - w- Z

““””””””..... .................”””-”.” ...........

..................

0---- .-,-,--,-------.----------- .-”-”------

~

-.-.+. _._._.-----

K

0

39- -

0

1-

a

2

37- -

$

z

$ 35

z

1

0

I I 1 I 1 ,

12 13 14 15 16 17

AGE IN YEARS

Figure 4, Mean hematocrit levels for youths aged 12-17 years, by annual family income, age, and sex: United States, 1966-70.

7
— Males, education of parent lessthan 8 years

------ Males, education of parent 13 years or more

is

z

47

45

43

41

39

[

---- ----- Females, education of parent lessthan 8 years

.. . . . . . . . ... Females, education of parent 13 years or more

.-4

**

./”

//

.“O /

....... . . .... ... ... . .....

~..

..... .. . . . . . . .. . ..... . . . .. . . . . . . . . ...* -

...... . ..-

.- .-.=.-.

-------- -------- ---- -----

----

-------- .-. *

*.-

37- -

35- “

1 I I t I t

12 13 14 15 16 17

AGE IN YEARS

Figure 5. Mean hematocrit levelsfor youths aged 12-17 years, by education of parent, age, and sex: United States, 1966-70.

and by education of parent, sex, and age (tables Negroes in the sample, especially at the higher

18 and 19) separately for white and Negro

youths.

The relationships between mean hematocrit

and annual family income and between mean

hematocrit and education of parent, discussed

previously for the population as a whole, held

also for white youths when examined separately.

Among white males and white females in all age

groups, a consistent increase in mean hematocrit

was found both with increase in annual family

income and with increase in education of parent.

When data were examined separately for each

age group (tables 17 and 19), there dld not

appear to be a consistent increase in mean

hematocrit of Negro youths with increase in

annual family income or with increase in education of parent. These estimates of mean hematocrit for Negroes, however, were quite unstable

because of the relatively small numbers of

income and education groups. To compensate

for this, the six age groups for females in tables

16 through 19 were collapsed into one table,

and the combined data were examined for Negro

and white female youths by education of parent

and by annual family income (table A and

figures 6 and 7). Even with all ages combined,

the Negro female youths did not show a

consistent increase in mean hematocrit with

increase in annual family income or with increase in education of parent. At all levels of

income and education, white female youths had,

mean hematocrits approximately 1.0-2.0 ml

percent higher than Negro females of comparable family income or parental education.

A similar analysis was not performed for

males because of the increase with age in mean

hematocrit observed in both Negro and white

males.
Table A. Sample size, mean hematocrits, and standard errors of the means for Negro and white female youths 12-17

years of age, by annual family income and education of parent

1ncome and education of parent

Annual family income

Lessthan $3,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$3,000-$4,999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$5,000-$9,999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$10,000 ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Education of parent

Lessthan 8years . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . .

8-n years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13yearsormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-

White females _

-------- -----

~

~

I

Negro females

!-

: o~

Lessthan $3,000- $5,000-$10,000

z

f $3,000 $4,999 $9,999 ormore

s

. ANNUAL FAMILY INCOME

Hematocrit in ml percent

495

400

407

117

302

679

363

127

39.3

38.9

39.7

39.4

38.9

39.4

39.8

38.5

.32

.49

.19

.72

.28

.22

.32

.90

928

1,102

3,760

3,258

784

2,337

3,600

2,752

40.2

40.3

40.6

41.0

40.1

40.4

40.8

41.0

.39

.24

.14

.15

.62

.19

.10

.17

45

40

35 1

White females

* ----------

ti----~

.

Negro females

o~

Less 8-11 12 130r

than 8 more

EDUCATION OF PARENT IN YEARS

Flaure6. Mean hematocrit for white and Nesrrofemalevouths Figure7. Mean hematocrit for white and Negro female youths

aged 12-17 years by annual family income: United States,

1966-70.

DISCUSSION

The packed cell volume, or hematocrit value,

is determined by centrifuging a standard amount

of whole blood at 12,500 r.p.m. for 5 minutes.

aged 12-17 years by education of parent: United States,

1966-70.

As a result of this procedure, the blood’s cells

are separated from the plasma and packed in the

lower portion of the tube. The resultant hematocrit packed red cell volume can be measured

very accurately.

9
The hematocrit value gives similar, but not

identical, information on the hematological status of a subject, as does a hemoglobin or red

blood cell count. Currently, the hematocrit is

the simplest and single most accurate measurement of anemia or polycythemia available to the

health profession. If the hematocrit is abnormal,

then the hemoglobin and the number of red cells

can be measured for more definitive hematological studies. Unfortunately, standard values for

adolescents are difficult to construct due to the

scarcity of studi& that controlled the numerous

variables influencing the normal hematocrit

value in adolescence.

There are many variables that influence

hematocrit values in healthy individuals, so that

healthy persons vary widely with respect to their

blood values.l 3 Small differences may be associated with such factors as height, weight, and

body types. Under ordinary circumstances, a

small diurnal variation of about 4 percent from

the mean hemoglobin has been observed. 14

Acute or chronic changes in hydration will

influence the hematocrit concentration. It has

been suggested that muscular activity can alter

hematopoietic values. For example, strenuous

exercise may lead to accelerated destruction of

red cells; 15 however, sustained exercise by

athletes can stimulate the erythropoietic system.

Olympic athletes have mean hemoglobins that

vary from 13.7 to 18.6 grams percent.l 6 Because of this, blood values obtained after extreme exercise are of dubious significance. Extreme excitement resulting in erythrocytosis has

been described. 17 On the other hand, climate,

temperature, and season have relatively little

influence on blood values. 18 Studies reporting

on racial differences in erythropoietic values are

few, inconclusive, and deal primarily with

adults. 18 ~19 Low barometric pressure, which

increases anoxemia, is accompanied by a compensatory increase in erythrocyte count and

thus in the quantity of hemoglobin. The magnitude of the response depends on the degree,

duration, and constancy of exposure to the low

barometric pressure associated with high altitude.d Sustained exposure to high altitudes over

months or years will lead to an increased

‘A preliminary analysis of unweighed data showed the

expected altitude gradient with a range of approximately 8 ml

percent.

concentration of red cells. 13 The significant

physiologic factors (i.e., excluding diseases) affecting the erythrocyte count are (1) extreme

physical exercise or excitement, (2) severe dehydration, (3) age, (4) sex, and (5) high altitude. zo

Age and sex, two of the most sibmificant

variables in this type of study, were carefully

controlled in this survey. Extreme physical

exercise, excitement, and high altitudes play a

casual role in the results in this study. Severe

dehydration, an uncommon event in an ambulatory population, is also a most unlikely factor

that could possibly affect the results of the

investigation.

Finally, most of the data reported in the

literature differ from those of the HES because

of the omission of those subjects who were

anemic or suffered from recent blood loss, poor

nutrition, and diseases of the blood. Therefore,

those results are not strictly comparable to HES

data, which were obtained from a population at

large with no specific medical exclusions.

Anemia in some of our sample subjects may

significantly affect the outcome of these HES

data. (This important variable will be discussed

fully under racial differences.) It has been

demonstrated in a recent study that a normal

juvenile population given therapeutic iron for a

period of 3 months will show an increase in

hemoglobin and mean corpuscular hemoglobin

concentration.z 1 However, there was no change

in mean hematocrit values, indicating that a mild

iron deficiency will not affect mean population

hematocrit values. When using and interpreting

HES values, it is important to keep in mind that

these values represent the hematocrit status for

the entire U.S. population aged 12-17 years and

may or may not represent the optimal or

maximal hematocrit values for this age group.

Age and Sax

Striking variations in erythropoiesis are

known to be associated with age and sex. In

these HES data, adjustment for age and sex is

critical because the major differences in erythrocyte formation between males and femaIes

first occur during adolescence. In order to

demonstrate this, studies need to be carefully

designed to control for age and sex; most of the

studies in the literature have failed to do this.

10
The effect of age and sex on hematocrit

during childhood is not striking. Reported

studies indicate a slight rise in hematocrit during

childhood with no difference between boys and

girls. 13 ~~1~Zz During adolescence, girls in the

present study have a stable hematocrit, with

little if any change with age (tables 1 and 3).

This is also true in the few comparable studies

that are available in the literature. Z1‘z 3 In sharp

contrast, boys who enter adolescence with a

hematocrit similar to that of girls show a steady

increase with age during adolescence, almost

reaching their adult values by the 17th year

(tables 1 and 3). The increase in hematocrit in

boys appears to reach its maximum between the

ages of 14 and 14% years. These ages are the

period of life when many of the boys would be

experiencing the biological expression of pubescence. Therefore, more than a casual relationship between the events of pubescence and

changes in hematocrit in males is suggested. It

has already been shown that increment in

hemoglobin in adolescent males is closely related

to the events of pubescence. z A The postulation

that this increase in erythropoiesis in the male is

induced by androgens is compatible with our

observations on males of same age.zs Thus, the

sex difference in hematocrit develops in the

13th year in our population and widens perceptibly by the 17th year. In a similar and

comparable study of Swedish children and adolescents, the significant sex difference in

hematocrit also occurred during the 13th

ye:ir. z 1

By age 15, most teenage girls are menstruating. The daily loss of iron through menstruation

ranges from 0.1 to 4.0 mg/day, the average being

0.7 mg.~ G Under normal living conditions and

with an adequate diet, the teenager is able to

replace these additional iron losses. If the diet is

inadequate or if pregnancy with its higher iron

requirement occurs, the teenage female may

develop anemia.

Race

In one earlier study of healthy adult men, no

racial differences in hemoglobin, hematocrit, or

erythrocyte count were detected. z 7 Subsequently, Cycle I HES data showed that with the

exception of males aged 18-24, white adults had

consistently higher mean hematocrits than

Negro adults.

Differences in blood values between various

samples of Negro and white children and adolescents have been reported recently. Owenz 8 has

reported a significantly lower hemoglobin in

young Negro children compared with that in

white children, even though an adequate amount

of circulating iron in the serum was demonstrated. Pearson reported a prevalence of anemia

(which he defined by a hematocrit value less

than 34 ml percent) in Negro girls aged 14-17

years of 8.0 percent and a prevalence of anemia

(as he defined by a hematocrit value less than 36

ml percent) in Negro males aged 14-17 years of

1.2 percent.z 9 Unfortunately, Pearson’s study

had no white subjects to be used as a comparative reference. Data from the recent l.O-State

Nutrition Survey suggest that hematocrit values

of Negroes are lower than those of white persons

at most ages.30 In addition, the study found

that Negro children 6-12 years of age in States

with both low and high income ratios have lower

hematocrits than white children of the same age

group. Further, it was found that only in States

with low income ratios were the hematocrit

values for Negro children 2-5 years of age lower

than those for white children. Most recently, the

preliminary findings from the Health and Nutrition Examination Survey (HANES). of the

National Center for Health Statistics, which have

just been published,a 1 estimate mean hematocrit values for white youths 12-17 at 42.2 ml

percent and those of Negro youths at 40.2 ml

percent.

In the currently reported HES survey of

youths 12-17 years of age, racial differences

between Negro and white adolescents are very

apparent. Because of the size and nature of the

sample, these currently reported HES estimates

are much more reliable than those referred to

above. Both male and female white youths have

consistently higher mean hematocrit values than

Negro male and female adolescents, with differences between Negro and white youths being

more apparent in females than in males and

most apparent among older female adolescents

(table 7). Descriptively, our findings further

show th?t a substantially greater percentage of

Negro female youths have hematocrit values

below 35, 37, or 39 ml percent at all ages than

.

11
white girls; the same is true, although to a lesser

extent, of Negro male youths when compared

with white males of similar age.

It is unlikely that the racial differences in

hematocrit found in our survey can be explained

by anemias resulting from abnormal hemoglobin. The prevalence of sickle cell disease, sickle

cell trait, and thalassemia, all known to cause

anemia, was found to be only 0.24 percent in a

group of Job Corps enrollees. I g This low prevalence of anemia due to abnormal hemoglobin

could not explain the racial differences found

in our population.

One determinant of low hematocrit in adolescent girls is the occurrence of pregnancy with its

higher demands for dietary iron at a time when

growth and onset of menstruation also require

increased iron. When this demand for increased

iron is superimposed on chronically marginal

nutritional intakesj excessively low hematocrits

might result. This might be particularly true of

Negro girls, since the rate of pregnancy for

females of races other than white has been

reported to be 11 times that of white girls

between the ages of 10 and 14 years and 2.4

times that of white girls between the ages of 15

and 19 years.32 This may partially explain the

excessive number of Negro girls with low hematocrits, particularly as age increases.

If we apply Pearson’s criterion for anemia in

females (hematocrit less than 34 ml percent) to

HES data, we would estimate that 6.8 percent of

Negro adolescents 14-17 years of age are anemic,

which closely compares with a prevalence of b.O

percent found by Pearson. Likewise, applying

Pearson’s criterion for anemia in males (hematocrit less than 36 ml percent), we would extrapolate from HES data that 1.9 percent of Negro

youths 14-17 years of age are anemic, a prevalence very close to the 1.2 percent found by

Pearson for Negro males 14-17 years old. z 9

It is quite apparent from the recent reports

mentioned previously as well as from HES data

that a significant difference exists between

hematocrit values for Negro and white teenagers.

Furthermore, this difference is greater between

females than between males. It is unlikely that

all of the difference is due to an excessive

proportion of cases of anemia among Negroes.

There remains an apparent residual racial difference in the comparative percentile distributions

(even at the 50th and 95th percentiles) among

females that cannot be satisfactorily explained

by these HES data.

income and Education

There is clear evidence that level of family

income is related to the level of hematocrit in

both boys and girls (table 13 and figure 4). This

effect is much more pronounced at the 10th

percentile of the distribution than at the 90th

percentile (table 8).

In a similar fashion, the level of education is

clearly correlated with the level of hematocrit in

the population. This i. apparent at all ages for

both boys and girls (table 15 and figure

5). This observation is not unexpected, since

education and family income are known to be

highly correlated.

Presumably, the major part of this socioeconomic effect lies in the greater amount of

anemia found in lower socioeconomic groups.

Perhaps, a rise in income results in better

nutrition or medical care and, hence, a decrease

in the likelihood of developing anemia. Alternatively, there may be a tendency fcir “anemic”

families to be less successful economically. When

interpreting associations between income and

conditions of ill health, there is always the

question of whether ill health is a result of low

income or whether it is a cause. The present

data, however, cannot ascertain which, if either,

of these hypotheses is the important determinant of the observed socioeconomic differences.

Interaction Between Race and Socioeconomic

Status

An important finding in these data is the lack

of a clearcut increase in hematocrit with increase

in socioeconomic status among Negro adolescents (tables 17 and 19). Even when all the age

groups for females were combined (table A),

there appeared to be no consistent socioeconomic effect for Negro females. The explanation

for this may be nutritional. That is, even as

Negro families rise up the socioeconomic ladder,

they may stall maintain their dietary habits of

less affluent periods. Alternatively, there may be

genetic or physiological factors that affect

hematocrit and are resistant to changes in

socioeconomic status. Again, it cannot be deter12
mined from the present data which, if any, of

these speculations is the important determinant

of the lack of a strong socioeconomic effect

observed in Negro adolescents.

There was, however, in white adolescent

males and females, a consistent increase in mean

hematocrit with increase in socioeconomic status as measured by either family income (table

16) or education of parent (table 18). Since

there was no age effect in female adolescents, it

was possible to combine age groups for Negro

and white females and, hence, to examine

Negro-white differences at each level of income

or education (table A). From this, it appears

that the differences in mean hematocrit between

white females at the highest socioeconomic

levels (annual family income of $10,000 or more

or education of parent of 13 years or more) and

those at the lowest end (annual family income

less than $3,000 or education of parent less than

8 years) are generally smaller than the differences observed between white and Negro female

youths of comparable socioeconomic status.

General Comparability With Other Studies

There are only a few studies in the literature

with which HES data can be somewhat compared. Unfortunately, most of the studies either

combine boys and girls during adolescence and

calculate a mean value or otherwise construct

tables or arrange the data by age in such a way

that makes a comparison with these HES data

difficult.

Dibble,z 3 however, reported a study in which

the hematocrit values of boys and girls 12-15

years of age can be compared with those of HES

youths. The hematocrit values among 12-yearold boys in three different school populations

ranged from 38.7 ml percent to 43.0 ml percent;

and for 15-year-olds, the range was from 43.3 ml

percent to 45.0. The mean for HES boys at age

12?4 was 40.5 ml percent and at age 15%, 43.9

ml percent, For 15-year-old girls, the range was

from 37.1 ml ~ercent to 40.7. Similarly, the

mean for HES girls at age 12Y2 was 40.3 ml

percent and at 15%?, 40.7. Thus, the data

between the two studies are quite comparable.

Wlntrobe,l 3

normal values,

years and then

.& .

a frequently cited reference for

grouped data by age up to 15

reported normal values for adult

males and females. At ages 11-15 years, the

overall mean hematocrit is 39.0 ml percent. His

published mean values for adult females and

adult males are 42.0 and 47.0 ml percent,

respectively. The most comparable HES females

and males (i.e., 17-year-olds) have hematocrit

values of 40.6 and 45.8 ml percent, respectively.

Both values are slightly under the values found

by Wintrobe. It appears that HES values would

be similar to Wintrobe’s if the age limits of our

population had been extended into their

twenties. Further comparisons with Wintrobe’s

normal data are not valid because of the

grouping of his data.

Albritton’sz z standard values for 12-year-old

boys and girls combined are slightly lower (39.6

ml percent) when compared with HES boys

(40.5 ml percent) and girls (40.3 ml percent) of

the same age. For boys and girls 14 years and

over, Albritton’s standard values are 47.0 and

42.0 ml percent, respectively. HES boys and

girls aged 17 years have a mean hematocrit of

45.8 and 40.6 ml percent, respectively; both

values are slightly lower than Albritton’s.

Pearsonz g reported the hematocrit values for

a large number of Negro children and youths.

Again, his grouping of data during adolescence

makes comparisons difficult. For Negro males

aged 14-17 years in the Pearson study, mean

hematocrit was 43.2 ml percent, whereas for

those similarly grouped by age in the HES, the

overall mean was 43.6 ml percent. For females

1417 years, the mean hematocrit was 38.8 ml

percent compared with that of 38.9 ml percent

for comparable females in the HES. Thus the

data from Pearson’s study and the national

estimates from the HES for Negroes aged 14-17

years are, on comparison, almost identical. A

recent Norwegian study reports hematocrits for

each year of age from 7 through 20 years. z 1 The

mean hematocrit for bo ys at age 12 years is 40.7

ml percent (40.5 for those in the HES) and at 17

years, 45.2 ml percent (45.8 for those in the

HES). For girls at age 12, the mean hematocrit

was 41.0 ml percent (40.3 for those in the HES)

and at 17 years, 41.1 ml percent (40.6 for those

in the HES). The data are remarkably comparable, most especially that for boys. Finally, the

most recently available comparison of these HES

data is that with the preliminary findings of the

HANES data referred to earlier,31 in which the

13
overall mean values are almost identical: In both

the HES and the HANES, mean hematocrits of

males aged 12-17 years are estimated to be 43.1

ml percent, while those for females in the

HANES are estimated to be 40.7 ml percent and

in the HES, 40.5 ml percent. Thus, the mean

values of HES hematocrit data compared with

similar data in the literature on adolescence are

in close agreement.

The HES data can also be compared with two

studies of young adults. First Greendyke’s 27

study of 950 healthy enlisted men aged 17-29

years (with exclusions for any factor known to

affect normal blood values) found the mean

hematocrit to be 45.8 f 2.5 ml percent, again

quite close to HES values. Second, current data

on teenagers can be compared with Cycle I data

for adults (tabIe 20).18 It appears from the

combined Cycle I and Cycle III data that the

increase with age in mean hematocrit observed

in Cycle III adolescents continues in males 18-24

years oId (as observed from Cycle I data), but at

a much sIower rate, until “mature” levels of

about 47.0 ml percent are reached. There then

appears to be a decrease in mean hematocrit

with age beginning with the age group 45-54

years. In Cycle III females, there was little or no

apparent increase in mean hematocrit observed

at ages 12-17. The mean hematocrit Ievel for

17-year-old adolescent females was 40.6 ml

percent and 41.4 ml percent for females aged

18-24. This would be compatible with an annual

increase of 0.2 ml percent beginning with age

17. Female hematocrits seem to increase during

adulthood to levels over 43 ml percent among

postmenopausal women.

It appears from Cycle I data “that mean

hematocrit increases slowly throughout the

adult life of women to reach levels of 43.7 ml

percent around age 60. The data from Cycle III,

however, indicate little if any evidence of

increase during adolescence. Therefore, #o account for the difference of 0.8 ml percent

between 17-year-oId females in Cycle III and

those aged 18-24 years in Cycle I, one would

have to hypothesize that the increase observed

in Cycle I adult women begins shortly after age

18 or that there is a systematic artifact that gives

artificially high levels to the Cycle I data. One

would tend to reject the latter hypothesis,

because the laboratory artifact would also have

to be operating on the men, and the observed

curve for men appears completely reasonable.

Finally, the question can be raised concerning

the use of these data. Can the data be used as

optimal physiological standards, or is their use

restricted to being descriptive of the adolescent

population in the United States during the

sampling period? It is obvious that this is a

representative sample for the United States that

also includes all the abnormally low and high

values secondary to disease. It is of interest,

however, that the HES results for adolescents

are almost identical to those reported by

Natvig.21 His study had one characteristic that

is important to note. After initial measurements

of blood indexes, a group of Norwegian children

and adolescents were given elementaI iron for 3

months. During this period, there was a significant rise in hemoglobin and mean corpuscular

hemoglobin concentration, indicating mild iron

deficiency in his “normal” population. At the

same time, there was no change in their hematocrit. Therefore, the hematocrit may be normal in

mild iron deficiency. The suggestion that HES

data for adolescents may be quite close to or

even representative of the optimal hematocrit

values for adolescents could be supported by the

similarity between the Norwegian and HES data

on hematocrits during adolescence.

14
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11Robt.rts, D. F., and Hioms, R. W.: The dynamics of raciaf

intwmixturc. Am. J.Hum. Genet. 14(3):261-277, Sept. 1962.

12Rccd, T. E.: Caucasian genes in American Negroes. Science

165(3895):762-768, Aug. 22, 1969.

13Wiitrobe, M. M.: Clinical Henratologv, ed. 6. Philadelphia.

Lea and Febiger, 1967, p. 91.

14Brown, A., and Goodafl, A. L.: Normrd variations in blood

hemoglobin concentration. J.Physiol. 104(4):404407, Apr.

1946.

15Kmonen, M. J., and Kunnas, M.: Erythrocyte and

hemoglobin changes during protracted heavy muscular work.

Ann. Med.Exper.etBiol.Fennr2te 30:180-185, 1952.

16Berry, W. T. C. et af.: The diet hemoglobin vrdues, and

blood pressures of Olympic athletes. Br.Med.J. 1:300-304, Feb.

19, 1949.

17Wintrobe, M. M.: The erythrocyte in man. Medicine

9(2):195-255, May 1930.

18Nation~ Center for Health Statistics: Mean blood hematocnt of adults, United States, 1960-1962. Vital and Health

Statistics. Series 11, No. 24. DHEW Pub. No. (HShl) 73-1080.

Health Services and Mental Herdth Adrninktmtion. Washington.

U.S. Government Printing Office, Apr. 1967.

19Field@, J., Batilden, P., Tolbert, G., Bennett, R.> ad

Nelson, S. H.: A coordinated sickle celf program for economically disadvantaged adolescents. Am.J.Publ 64(5):427-432, hlay

1974.

%fiale, J. B.: Laborato~ Medicine –Henratology. St. Louis.

C. V. Mosby CO., 1958, p. 296.

21Natvig, H. et al.: Studies on hemoglobin vafues in Norway.

ActaMed.Stand. 182:183, Aug. 1967.

22A1bntton, E. C. (cd.): Standard Values in Blood. Philadelphia. W. B. Saunders Co., 1952.

23Dibble, M. V. et af.: Some preliminary biochemical

findings in junior high school children in Syracuse and Onondaga

County, New York. Anr.J. CZin.Nutr. 17(4): 218-239, Oct. 1965.

2’%oung, H. B.: Aging and adolescence. Dev.Med. Child

Neurol. 5:451, 1963.

25 Kennedy, B. J., and Gdbertsen, A. S.: Increased erythropoiesis induced by androgenic-hormone therapy. N.EngLJ.Med.

4

256 16):719-726, Apr. 18, 1957.

6World Health Organization: Nutritional Anaemias. WHO

Tech.Reposer., No. 405, Genev~ 1968.

27Greendyke, R. M. et al.: A suggested revision of normaf

values for hemoglobin, hematocrit, and erythrocyte count in

healthy adult men. Techn. Bull. Regist. Med. Techn.

k

32(3 .41-48, Mar. 1962.

2 Owen, G., Lubin, A. H., and Garry, Philip J.: Preschool

children in the United States: Who has iron deficiency?

J.Pediatr. 79(4):563-568, Oct. 1971.

29Pearson, H. A., McLean, F. W., and Brigety, R. E.: Anemia

related to age: Study of a community of young black Americans.

JAMA 215(12):1982-1984, Mar. 22, 1971.

15
30Center for Disease Control: Ten-State Nutrition Survey in

the United States, 1968-1970. IV. Biochemical. DHEW Pub. No.

(HSM) 72-8132. Atlanta. Health Services and Mental Health

Administration. 1972.

31National Center for Health Statistics: Preliminary Findings

of the First Health and Nutrition Examination Survey, United

States, 1971-1972: Dietary Intake and Biochemical Findings.

DHEW Pub. No. (HRA) 74-1219-1. Health Resources Administration. Washington. U.S. Government Printing Office, Jan.

1974.

32National Center for Health Statistics: Teenagers: Marriages, divorces, parenthood, and mortality. Vital and Health

Statistics. Series 21, No. 23. DHEW Pub. No. (HRA) 741901.

Health Resources Administration. Wash@on. U.S. Government

Printing Office, Aug. 1973.

33Nationaf Center for Health Statistics: Sample design and

estimation procedures for a national health examination survcy

of children. Vital and Health Statish”cs. Series 2, No. 43. DHEW

Pub. No. (HRA) 741005. Health Resources Administration.

Washington. U.S. Government Printing Office, Aug. 1973.

3%ational Center for Health Statistics: Cycle I of the Health

Examination Survey: Sample and response, United States,

1960-62. Vital and Health Statistics. PHS Pub. No. 1000-Series

1l-No. 1. Public Health Service. Washington. U.S. Government

Printing Office, Apr. 1964.

35Nationaf Center for Health Statistics: Replicatiorx An

approach to the analysis of data from complex surveys. Vital and

Health Statistics. PHS Pub. No. 1000-Series 2-No. 14. Public

Health Service. Washington. U.S. Government Printing Office,

Apr. 1966.
LIST OF DETAILED TABLES

Table 1,

2.

3.

4.

5.

6.

7.

8.

9.

10,

11.

12.

13.

14.

15.

16.

17.

Estimated number of youths aged 12-17 years in the population by hematocrit group and selected characteristics of

hematocrit distribution, by sex and age: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent distributions of youths aged 12-17 years by hematocrit intervals, according to sex and age: United States,

1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mean hematocrit, standard deviation, standard error, and percentiles for youths aged 12-17 years, by sex and by age

in%year intervals: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Means, medians, differences between means and medians, differences between medians and 5th percentiles,

differences between 95th percentiles and medians of hematocrits, and a ratio for youths aged 12-17 years by sex and

age: United States, 1966-70.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mean hematocrits and standard errors of themeans for youths aged 12-17 years, bygaographic region, sex, and age:

United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Number of youths aged 12-17years inthesample of the Health Examination Survey, bygeographic region, sex, and

age: United States, 1966-70.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mean hematocrits and standard errors of the means for youths aged 12-17 years, by race, sex, and age: United

States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ditierences between white and Negro youths aged 12-17 years with respect to selected percentiles of hematocrit

levels: UnitedStates,1966-70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Number of youths aged 12-17 years in sample of the Health Examination Surveyrby race, sex, and age: United

States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Estimated number of white youths aged 12-17 years in the population by hematocrit group and selected

characteristics of hematocrit distribution, bysexand age: United States, l966-7O . . . . . . . . . . . . . . . . . .

Estimated number of Negro youths aged 12-17 years in the population by hematocrit group and selected

characteristics of hematocrit distribution, bysex and age: United States, 1966-70 . . . . . . . . . . . . . . . . . .

Percent of youths with hematocrit determinations below certain levels, byage, sex, and race . . . . . . . . . . . .

Weighted sample size, mean hematocrits, and standard errors of the means for youths by age, sex, and normal family

income: UnitedStates, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10th, 50th, and 90th percentiles of hematocrit distributions for youths by age at last birthday and sex for the

following income groups: lessthan $4,000 and$lO,OOOOr more: United States, 1966-70 . . . . . . . . . . . . . .

Weighted sample size, mean hematocrits, andstandard errors of themeans foryouths, byage, sex, and education of

parent: UnitedStates, 1966-70.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Weighted sample size, mean hematocrits, andstandard errors of themeans forwhite youths, byage, sex, and annual

familyincome: UnitedStates, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Weighted sample size, mean hematocrits, and standard errors of the means for Negro youths, by age, sex, and annual

family income: UnitedStates, 1866-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

19

20

21

21

22

22

23

23

24

25

26

27

28

28

29

29

30

17
LIST OF DETAILED TABLES–Con.

Page

Table 18. Weighted sample size, mean hematocrits, and standard errors of the means for white youths, by age, sex, and

education ofparent: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

19. Weighted sample size, mean hematocrits, and standard errors of the means for Nagro youths, by age, sex, and

adulation ofparent: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

20. Mean hematocrit byageand sex for HESCycle llland Cycle ldata . . . . . . . . . . . . . . . . . . . . . . . . . 31

18
Table 1. Estimated number of vouths aaed 12-17 years in the population by hematocrit group and selected characteristics of hematocrit distribution,

by sex and age: United States, 1886-70

I

Male Female

12 13 14 15 16 17 12 13 14 15 16

years years years years years years years years years Vears years

Selected variable

.

17

years

Hematocrit group Estimated number of youths in POPUlation in thousands

1.970 1,946

3

27

65

352

588

466

286

101

48

11

YwE! All groups . . . . . . . . . . . . . . .

Undw29.0ml percent . . . . . . . . . . .

2,032 2,008 E!-l-E! 1,836 1.764

3

10

73

248

3

35

132

322

465

489

305

173

24

3

2

16

81

208

364

454

436

3

7

31

71

242

555

434

322

118

44

9

3

3

5

26

69

433

608

410

251

56

30

5

3

9

18

78

343

561

427

257

112

29

6

6

3

3

12

20

91

343

537

434

3

2

10

21

93

278

521

410

303

65

36

4

35.8

37.3

39.2

40.7

42.7

44.2

45.3

17.50

40.6

2.84

.16

8

10

57

135

386

479

450

173

49

15

18

94

391

2

2

15

130

328

652

487

297

89

24

3

36.0

37.3

39.1

40.6

42,4

44.1

45.2

12.54

40.5

2.87

.17

29.0-30,9 ml percent

31.0-32.9 ml percent

33.0-34.9 ml percent

35.0.36.9 ml percent

37.0-38.9 ml percent

39.0-40.9 ml percent

41. C-42.9 ml percent

43.044,9 ml percent

45.0-46.9 ml percent

47.0.48.9 ml percent

49.0.50.9 ml percent

51.0.62.9 ml percent

53.0-54.9 ml percent

55.0-56.9 ml percent

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

496 608

554

376

159

71

16

37.1

38.2

40.0

41.8

43.3

45.2

48.3

13.49

41.5

2.86

.20

506

305 268

39

6

3

58

19

3

36.2

37.3

38.6

40.4

42.4

44.1

44.7

16.49

40.4

2.73

.18

200

99

27

3

3

57. Omlpercentandwer . . . . . . . . . . 6

Percentile

6th . . . . . . . . . . . . . . . . . . . . . . . .

10th . . . . . . . . . . . . . . . . . . . . . . .

26th, . . . . . . . . . . . . . . . . . . . . . .

both, . . . . . . . . . . . . . . . . . . . . . .

76th, . . . . . . . . . . . . . . . . . . . . . .

90th . . . . . . . . . . . . . . . . . . . . . . .

95th . . . . . . . . . . . . . . . . . . . . . . .

Mean age at time of examination

(inyears) . . . . . . . . . . . . . . . . . .

Mean hematocrit inmlpercenf . . . . . .

Standard deviation inml percent . . . . .

Standard errorofmean . . . . . . . . . . .

Hematocrit in ml percent

38.1 40.3

41.7

43.2

45.0

47.1

48.8

49.9

16.47

44.9

2.99

.21

41.2

42.4

44.2

46.1

48.0

49.6

50.3

17.51

45.8

2.82

.16

36.8

37.6

38.9

40.4

42.3

43.4

44.3

12.53

40.3

2.37

.17

37.0

37.8

39.2

40.7

42.6

44.3

45.8

13.48

40.7

2.80

.16

36.7

37.6

38.7

40.3

42.2

44.0

44.9

14.49

40.3

2.77

.18

38.8

40.1

42.1

44.2

46.1

48.3

49.7

15.49

43.9

3.36

.21

36.7

37.7

39.1

40.6

42.7

44.5

45.7

15.51

40.7

3.00

.19

39.2

40.9

43.0

45.1

47.0

47.8

14.51

42.7

2.92

.17

19
Table2, Percent distributions of youths aged 12-17 years byhematocrit intervals, according tosex and age: United Statas, 1966-70

Hematocrit group

All groups , . . . .

Under 29.0 ml

percent . . . . . . . . .

28.0-30.9 ml percent . .

31.0-32.9 ml percent . .

33.0-34.9 ml percent .,

35.0-36.9 ml percent . .

37.0-38.9 ml percent . .

39.0-40.9 ml percant . .

41.0-42.9 ml percent . .

43.0-44.9 ml percent . .

45.0-46.9 ml percent . .

47.0-48.9 ml percent . .

49.0-50.9 ml parcant . .

51.0-52.9 ml percent . .

53.0-54.9 ml p¢ . .

55.0-56.9 ml percant . .

57.0 ml percent

And over . . . . . . . .

Male Female

12 13 14 15 16 17 12 13 14 15 16 17

years years years years years years years years years years years years

Percent distribution

100.0 I 100.0 I 100.0

.1

.1

.7

6.4

16.2

32.1

24.0

14.6

4.4

1.2

.1

.1

.5

3.6

12.4

24.7

27.6

18.7

7.9

3.5

.8

.2

1.8

6.8

16.5

23.8

25.1

15.6

8.9

1.2

.2

100.0

.1

.8

4.3

10.9

19.2

23.9

22.9

10.5

5.2

1.4

.2

.2

.3

100.0

.2

.4

1.7

3.9

13.2

30.2

23.6

17.5

6.4

2.4

.5

100.0

.5

.6

3.2

7.7

21.9

27.2

25.5

9.8

2.8

.9

100.0

.9

4.8

19.8

30.9

25.7

15.5

2.0

.3

.2

100.0

.2

1.4

3.3

18.1

30.2

23.9

14.7

5.2

2.5.

.6

100.0

.2

.2

.3

1.4

3.6

22.8

32.0

21.6

13.2

2.9

1.6

.3

100.0

.2

.5

1.0

4.2

18.5

30.3

23.1

13.9

6.1

1.6

.3

.3

100.0

.2

.2

.7

1.1

5.1

19.2

30.0

24.3

15.0

3.1

1.1

.2

100.0

.2

.1

.6

1.2

5.3

15.9

29.8

23.5

17.4

3.7

2.1

.2

Note. –Percents may not add to 100.0 due to rounding.

20
Table 3, Mean hematocrit, standard deviation, standard error, and percentiles for youths aged 12-17 years, by sex and by age in %-year

intervals: United States, 1966-70

F

40.4

40.5

40.9

41.5

41.9

42.7

43.3

44.0

44.4

44.9

45.3

45.8

46.0

39.9

40.3

40.7

40.8

40.6

40.2

40.2

40.8

40.5

40.4

40.6

40.5

40.6

Percentile

25

Sex 5X ST

3.11 .47

2.52 .15

2.85 .24

2.85 .19

2.71 .20

2.87 .22

3.19 .15

3.24 .23

3.41 .27

2.79 .24

2.83 .?0

3.14 .22

2.28 .25

2.16 .22

2.45 .21

2.45 .18

2.82 .21

2.85 .20

2.77 .27

3.03 .19

3.03 .28

2.77 .17

2.64 .2a

2.67 .24

2.90 .20

3.33 .37

5 10 50 75 90 95

Male

12yews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12!4 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13!: years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14ytxrrs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14)L years, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15Xycars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16% years, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17ycars, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17!4 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35.2

36.7

36.6

37.0

38.0

38.1

38.4

39.0

39.4

40.4

41.4

40.7

42.8

36.4

36.2

37.2

37.0

36.2

37.1

35.9

37.2

36.2

36.4

36.3

35.8

35.7

35.7

37.6

37.9

38.1

38.7

39.2

39.4

40.2

41.0

41.7

42.3

41.9

43.2

37.5

37.5

38.0

37.8

37.7

37.7

37.2

38.1

37.2

37.3

37.7

37.2

37.2

38.9

39.1

39.3

40.0

40.2

41.1

41.3

42.2

42.7

43.2

43.4

44.1

44.7

38.6

38.8

39.3

39.1

38.9

38.6

38.6

39.1

38.8

38.9

39.2

38.9

39.5

40.5

40.4

41.1

42.0

42.2

43.1

43.2

44.6

44.8

45.1

45.3

46.1

46.3

40.2

40.4

40.8

40.8

40.3

40.2

40.3

40.6

40.4

40.3

40.8

40.4

41.1

42.7

42.3

43.0

43.4

43.8

45.0

45.3

46.0

47.1

47.1

47.5

48.1

48.0

41.6

42.4

42.4

42.6

42.6

42.2

41.9

42.7

42.6

42.4

42.6

42.6

42.7

44.4

44.1

44.7

45.1

45.8

46.7

48.1

48.2

48.3

48.7

49.1

50.2

48.9

42.8

43.4

43.8

44.3

44.6

43.8

44.1

44.8

44.2

44.1

44.1

44.3

44.3

45.7

44.8

45.7

47.0

47.0

47.6

49.1

49.9

49.3

49.7

50.5

50.8

49.7

43.5

44.2

45.1

45.7

45.7

44.4

45.6

45.8

45.1

44.9

44.4

45.7

45.6

Female

12yedrs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12!4 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13ytx.ws. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13?4years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14yoars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14% years . . . . . . . . . . . . . . . . . . . .’ . . . . . . . . . . .

15yews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15!4 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16’A years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17%years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 4. Means, medians, differences between means and medians, differences between medians and 5th percentiles. differences between 95th

percentiles and medians of hematocrits, and a ratio for youths agad 12-17 years by sex and age: “Unitad States, 1966-70

Male Female

12

years

40.5

40.6

-0.1

4.6

4.6

1.00

13

years

41.5

41.8

-0.3

4.7

4.5

0.86

14

years

42.7

43.0

-0.3

4.9

4.8

0.98

15

years

43.9

44.2

-0.3

5.4

5.5

1.02

16

years

44.9

45.0

-0.1

4.7

4.9

1.04

17

years

45.8

46.1

-0.3

4.9

4.2

0.86

12

years

40.3

40.4

-0.1

3.8

3.9

1.03

13

yeers

40.7

40.7

0.0

3.7

5.1

1.38

14

years

40.3

40.3

0.0

3.6

4.6

1.28

15

years

40.7

40.6

+0. 1

3.9

5.1

1.31

Selected variable

16

years

17

years

Mcan(ml percent) . . . . . . . . . . . . . .

Median (ml percent) . . . . . . . . . . . . .

Mean-median (mlpercent) . . . . . . . . .

50th.5th percentile (ml percent) . . . . .

95th-50th percentile (ml percent) . . . .

40.4

40.4

0.0

4.2

4.3

1.02

40.6

40.7

-0.1

4.9

4.6

0.94

~atiO 95th.50th

50th-5th’”’”’”””””””””””

21
Table 5. Mean hemetocrits and standard errors of the means for youths aged 12-17 years, by geographic region, sex, and age:

United States, 1966-70

Total Northeast Midwest South West

1 1

Sex and age Total I I Northeast Midwest I South\ West

Male Mean hematocrit in ml percent Standard error in ml percent

40.0

41.1

42.7

43.6

44.6

45.6

40.4

40.4

39.9

40.5

39.7

39.9

40.7

41.8

42.9

44.4

45.8

46.2

40.1

41.2

40.4

40.9

40.2

40.6

.17

.20

.17

.21

.21

.16

.17

.16

.18

.19

.18

.16

.18

.30

.26

.44

.26

.28

.38

.27

.29

.45

.25

.23

.37

.55

.27

.31

.22

.40

.28

.19

.43

.24

.22

.33

.22

.19

.47

.38

.33

.32

.27

.37

.31

.22

.57

.42

.65

.52

.48

.65

.75

.44

.31

.43

.61

.57

.53

.46

12 years . . . . . . . ...<.....

13years . . . . . ..i . . . . . . . .

14 years . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . .

16 years . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . .

40.5

41.5

42.7

43.9

44.9

45.8

40.3

40.8

40.3

40.7

40.4

40.6

40.7

41.4

42.7

43.9

44.9

45.9

40.5

40.8

40.3

40.5

40.6

40.5

40.5

41.5

42.6

43.9

44.3

45.5

40.3

40.6

40.5

40.8

40.9

41.2

Female

12years . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . .

Table6. Number of youths aged 12-17 yearsin the sample of the Health Examination Survey, by geographic region, sex, and age:

United States, 1866-70

11 1 1 1

Sex and age Total Northeast ‘ Midwest South west

Male — Number of youths

922 890

m’

3,!%15

643

626

618

613

556

489

3,223

547

582

586

503

536

469

870

173

162

156

137

124

118

771

Allages, 12-17years . . . . . . . . . . . . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . ..I. . . . . . . . . . . . . . . . . . . . . . . . 116 130 125

835 814 803

Female

All ages, 12-17years . . . . . . . . . . . . . . . . . . . . . . . . .

135

145

139

121

125

106

150

157

148

108

140

132

128

142

161

139

126

118

134

138

138

135

145

113

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22
Table7. Mmn hematocrits and standard errors of the means for youths aged 12-17 years, by race, sex, and age: United States,

1966-70

II I

Sex and age

Male

12ycwrs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13ymtrs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14yecirs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15ytmrs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 years . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17ycmrs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Female

12yews . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14ytx3rs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . .. . . . . . . . . . . . . . . . . .

17y0ws . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total White Negro

Mean hematocrit in ml percent

40.5

41.5

42.7

43.9

44.9

45.8

40.3

40.7

40.3

40.7

40.4

40.6

40.6

41.5

42.9

44.1

44.9

45.8

40.4

40.8

40.4

40.9

40.7

40.9

39.6

41.4

41.7

42.9

44.4

45.7

39.7

40.2

39.4

39.3

38.3

38.5

Total White Negro

Standard error in ml percent

.17

.20

.17

.21

.21

.16

.17

.16

.18

.19

.18

.16

.19

.21

.19

.25

.24

.16

.19

.18

.19

.18

.17

.17

.35

.41

.27

.32

.43

.47

.21

.29

.46

.39

.47

.51

TotIIe8. Differences between white and Negro youths aged 12-17 years with respect to selacted percentiles of hematocrit

levels: United States, 1966-70

Percentile in white youths minus percentile in Negro youths

Percentile I

Male I

Female

12 13 14 15 16 17 12 13 14 15 16 17

years years years years years years years years years years years years

5th . . . . . . . . . . . . . . . . . . . 1.2 1.7 1.5 1.7 0.6 0.8 0.6 3.1 2.1 3.8 4.4 3.9

both . . . . . . . . . . . . . . . . . . 0.9 -0.3 1.0 0.6 0.4 0.2 0.5 0.6 0.8 1.3 2.4 2.0

95ih . . . . . . . . . . . . . . . . . . -0.1 -1.1 0.4 -0.2 0.1 -0.1 0.7 -1.6 0.3 0.5 1.1 0.6

23
Table9. Number of youths aged 12-17 years in sample of the Health Examination Survey, by race, sex, and age: United States,

1866-70

Sex and age

Male

Allages, 12-17 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Female

All ages, 12-17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

II I

‘eta’ II ‘hi’e I ‘egro

3,545

643

626

618

613

566

489

3,223

547

582

586

603

536

469

Number of youths

3,047

540

542

527

525

496

417

2,688

455

490

484

425

441

393

479

101

80

88

84

57

69

520

88

91

101

73

93

74

24
Table IO. Estimated number of white youths aged 12-17 years in the population by hematocrit group and selected characteristics of hematocrit

distribution, bysex andage: United States, 1866-70

White male White female

12 13 14 15 16 17 12 13 14 15 16 17

years years years years years years years years years years years years

Selected variable

Hemamcrit group Estimated number of youths in population in thousands

All groups . . . . . . . . . . . . . . . 1,747 1,729 1,686 1,646 1,594 1,528 1,685 1,667 1,633 1,584 1,542 I 1,502

Under 29. Oml percent . . . . . . . . . . .

29.0-30.9 ml percent . . . . . . . . . . . .

31. O-32.9 ml percent . . . . . . . . . . . .

33. O-34.9 ml percent . . . . . . . . . . . .

35.0-36.9ml percent . . . . . . . . . . . .

37.0-38.9ml percent . . . . . . . . . . . .

39.0.40.9ml percent . . . . . . . . . . . .

41.0-42.9ml percent . . . . . . . . . . . .

43.0.44,9ml percent . . . . . . . . . . .

46.0-46,9ml percent . . . . . . . . . . . .

47.0-48,9ml percent . . . . . . . . . . . .

49.0.60.9mi percent . . . . . . . . . . . .

61.0.52.9ml percent . . . . . . . . . . . .

63.0-54.9ml percent . . . . . . . . . . . .

56.0.66.9ml percent . . . . . . . . . . . .

57.0mlpercentand ovar . . . . . . . . . .

10

101

252

575

445

264

73

24

3

36.4

37.6

39.3

40.7

42.5

44.1

45.2

12.54

40.6

2.59

0.19

8.8

4.5

4.3

67

200

434

513

319

133

51

11

37.2

38.2

40.0

41.8

43.2

45.1

46.2

13.49

41.5

2.68

0.21

9.0

4.4

4.6

23

88

289

410

409

296

146

22

3

38.3

39.5

41.1

43.1

45.1

47.0

48.0

14.51

42.9

2.s4

0.19

9.7

4.9

4.8

10

49

181

326

409

377

176

84

24

3

3

6

39.3

40.3

42.2

44.2

46.2

48.3

49.7

15.49

44.1

3.20

0.26

10.4

5.5

4.9

3

24

61

198

497

394

272

99

37

9

4

10

46

112

334

427

388

149

42

15

12

76

319

512

439

282

36

6

3

11

48

298

511

425

239

93

39

3

3

5

17

44

355

548

346

233

48

30

2

37.1

37.7

38.8

40.3

42.2

44.1

44.9

14.49

40.4

2.60

0.19

7.8

4.6

3.2

5

6

55

274

495

373

245

101

29

6

4

37.1

38.0

39.3

40.7

42.8

44.6

45.7

15.51

40.9

2.86

0.18

8.6

5.0

3.6

5

5

58

266

477

407

4

12

53

222

446

381

253

56

14

3

37.1

37.9

39.3

40.7

42.6

44.2

44.8

16.49

40.7

2.47

0.17

7.7

4.1

3.6

290

55

36

4

37.0

37.7

39.7

41.1

43.0

44.2

45.4

17.50

40.9

2.64

0.17

8.4

4.3

4.1

Percentile Hamatocrit in ml percent

5th . . . . . . . . . . . . . . . . . . . . . . . .

10th . . . . . . . . . . . . . . . . . . . . . . .

2Mh . . . . . . . . . . . . . . . . . . . . . . .

50th . . . . . . . . . . . . . . . . . . . . . . .

76th . . . . . . . . . . . . . . . . . . . . . . .

90th . . . . . . . . . . . . . . . . . . . . . . .

95th . . . . . . . . . . . . . . . . . . . . . . .

40.6

41.9

43.2

45.0

47.1

48.7

49.9

16.48

44.9

2.79

0.24

9.3

4.9

4.4

41.2

42.4

44.2

46.1

47.9

49.6

50.3

17.50

45.8

2.79

0.16

9.1

4.2

4.9

36.8

37.7

39.1

40.5

42.4

43.5

44.3

12.54

40.4

2.37

0.19

7.5

3.8

3.7

37.2

38.0

39.3

40.8

42.6

44.2

45.7

13.49

40.8

2.62

0.18

8.5

4.9

3.6

Mean age at time of examination

(inyears) . . . . . . . . . . . . . . . . . .

Mean hematocrit inml percent . . . . . .

Standerd deviation in ml percent . . . . .

Stendard errorofmeen . . . . . . . . . . .

95th-5th percentile . . . . . . . . . . . . . .

96th-50th percentile . . . . . . . . . . . . .

50th.5th percentile.. . . . . . . . . . . . .
Table If. Estimated number of Negro youths aged 12-17 years in the population by hematocrit group andsalected characteristics of hematocrit

Selected variable

Hematocrit group

All groups . . . . . . . . . . . . . . .

Under 29. Oml percent . . . . . . . . . . .

29. O-30.9ml percent

31.0-32.9 ml percent

33.0-34.9 ml percent

35.036.9 ml percent

37.@38.9ml percent

39.@40.9 ml percent

41.0-42.9 ml percent

43.0-44.9 ml percent

45.0-46.9 ml percent

47.&46.9 ml percent

49.0-50.9 ml percent

51.0-52.9 ml percent

53.0-54.9 ml percent

55. C-EJ5.9ml percent

57.0 ml percent and over . . . . . . . . . .

Percentile

5th . . . . . . . . . . . . . . . . . . . . . . . .

10th . . . . . . . . . . . . . . . . . . . . . . .

25th . . . . . . . . . . . . . . . . . . . . . . .

50th . . . . . . . . . . . . . . . . . . . . . . .

75th . . . . . . . . . . . . . . . . . . . . . . .

both . . . . . . . . . . . . . . . . . . . . . . .

95th . . . . . . . . . . . . . . . . . . . . . . .

Mean age at time of examination

(inyears) . . . . . . . . . . . . . . . . . .

Mean hematocrit inml percent . . . . . .

Standard deviation inml percent . . . . .

Standard errorofmean . . . . . . . . . . .

95th-5th percentile . . . . . . . . . . . . . .

95th-50th percentile . . . . . . . . . . . . .

5&h-5th percentile . . . . . . . . . . . . . .

distribution, bysex and age: United States, 1886-70

Negro male Negro female

12 13 14 15 16 17 12 13 14 15 16 17

years years years years years years years years years years years years

Estimated number of youths in population in thousands

280

2

2

6

28

77

72

43

33

16

35.2

35.9

38.1

39.8

42.0

43.9

45.3

12.55

39.6

2.98

0.35

10.1

6.5

4.6

262

3

10

6

48

51

42

57

26

16

4

35.5

37.3

38.9

42.1

44.2

45.4

47.3

13.46

41.4

3.79

0.41

11.8

5.2

6.6

256 ] 241

=i3 -

12 6

44 32

33 28

52 38

75 46

9 55

27 18

2 12

3

36.8

38.0

39.5

42.1

43.9

47.1

47.6

14.52

41.7

3.26

0.27

10.8

5.5

5.3

37.6

38.5

40.3

43.6

45.4

48.1

49.9

15.49

42.9

4.14

0.32

12.3

6.3

6.0

231

3

4

4

11

43

58

40

42

19

8

225

3

12

23

45

53

59

25

7

Hematocrit

40.0

41.0

42.7

44.6

47.2

49.1

49.8

16.45

44.4

4.00

0.43

9.8

5.2

4.6

40.4

42.4

43.4

45.9

48.2

50.0

50.4

17.57

45.7

3.0:

0.47

10.0

4.5

5.5

272

6

19

69

93

60

23

3

275

ml percent

3

16

17

54

77

42

47

5

9

7

36.2

37.1

38.3

40.0

41.5

42.8

43.6

12.48

39.7

2.32

0.21

7.4

3.6

3.8

34.1

35.7

38.3

40.2

42.4

44.4

47.3

13.43

40.2

3.62

0.29

13.2

7.1

6.1

266

3

9

26

75

60

64

18

8

3

35.0

36.1

38.1

39.5

41.4

43.6

44.6

14.46

39.4

3.49

0.46

9.6

5.1

4.5

3

3

12

23

64

58

46

12

11

2

33.3

35.2

37.7

39.4

41.3

43.3

46.2

15.50

39.3

3.62

0.39

11.9

5.8

6.1

243

3

3

7

15

32

76

61

27

13

5

32.7

34.7

37.0

38.3

40.2

42.3

43.7

16.47

38.3

3.28

0.47

11.0

5.4

5.6

237

-

3

2

6

9

40

57

72

25

13

10

33.1

35.1

36.7

39.1

40.6

42.8

44.8

17.50

38.5

3.82

0.50

11.7

5.7

6.0

26
Table 12. Percent ofyouths,with hematocrit determinations below certain levels, byage, sex, and race

Age and race

Total

12ytmrs . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . .

17 years . . . . . . . . . . . . . . . . . . . .

White

12ycars . . . . . . . . . . . . . . . . . . . .

13yews. . . . .. m. . . . . . . . . . . . .

14 years . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . .

16yuars . . . . . . . . . . . . . . . . . . . .

17 years, . . . . . . . . . . . . . . . . . . .

Nearo

12years, . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . .

14 years . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . .

16 years, . . . . . . . . . . . . . . . . . . .

17 years . . . . . . . . . . . . . . . . . . . .

Percentage of males with hematocrit

determinations below:

35.0 percent

0.9

0.6

0.2

0.1

0.2

0.6

3.6

5.0

1.2

0.8

1.3

37.0 percent

7.3

4.3

1.9

0.9

0.5

0.4

6.4

3.9

1.4

0.6

0.2

0.3

13.6

7.3

5.9

3.3

3.0

1.3

39.0 percent

23.5

16.7

8.7

5.2

2.2

1.0

20.8

15.4

6.6

3.6

1.7

0.9

41.1

25.6

23.0

16.6

4.8

1.3

Percentage of females with hematocrit

determinatiorrs below:

35.0 percent

0.9

1.5

1.9

1.6

2.3

2.1

0.7

0.7

1.5

0.7

0.6

1.1

2.2

6.9

4.5

7.7

11.5

8.4

37.0 percent

5.7

4.9

5.6

5.8

7.2

7.5

5,2

3.5

4.2

4.1

4.3

4.6

9.2

13.1

14.3

17.4

24.7

25.3

39.0 percent

25.5

23.0

28.4

24.4

26.4

23.3

24.1

21.4

26.0

21.3

21.5

19.4

34.6

32.7

42.5

44.7

56.0

49.4

r

27
Table 13. Weighted samp[esize, mean hematocrits, andstandard errors of themeans foryouths byaF, sex, andnormal fami[y income: LJnitedStates, 1966.70

12 years 13 years 14 years 15 years 16 years 17 years

N z *X N z Sx N F Sx N z ST N F % N z Sz

.%x and annual family income

Total male

All incomes . . . . . . . .

Lessthan $3,000 . . . . . . . . .

$3,000$4,999 . . . . . . . . . . .

$5,000’$9,999 . . . . . . . . . . .

$l0,0000rmOre . . . . . . . . .

Don<tknmw . . . . . . . . . . . .

Blank mrefused . . . . . . . . .

Total female

All incomes . . . . . . . .

Lewthan $3,000 . . . . . . . . .

$3,00M4,999 . . . . . . . . . . .

$5,(XXI.$9,999 . . . . . . . . . . .

$lO,~OrmOre . . . . . . . . .

Don’t know . . . . . . . . . . . .

Blink orrefused . . . . . . . . .

Hematocrtt in ml percent

1,951 [ 42.7 0.17

0.67

0.48

0.22

0.22

0.81

0.72

0.18

0.31

0.46

0.25

0.22

0.42

0.65

1,900 I 43,9 44.9 0.21 1,764

_ll_

44.6 0.W5 226

45.1 0.34 245

44.8 0.35 692

45.0 0.25 479

44.8 0.85 49

!v!-L!x

I

45.3 0.60

45.3 0.49

46,0 0,18

46.1 0.17

44.5 082

45.6 0.84

40.6 016

T

39.6 0.47

39.6 0.45

40.7 0.27

41,1 0.28

40.8 0.52

40.7 1.25

2,o32 40.51 0.17 2,0C6 41.5 0.20 !zL.L.E

I

0.53 201

0.49 265

0.30 719

0.24 616

0.47 62

OS’S 55

0,19 1,789

T

0.50 246

0.31 166

0.26 650

0.27 594

0.68 63

3,16 60

180

308

869

575

65

46

1,970

257

274

722

600

79

37

1

39.8 0.38

40.2 0.38

40.6 0.24

40.6 0.21

40.9 0.57

41.2 0.89

40.3 0.17

T

40.2 0.45

40.0 0.35

40.3 0.25

40.7 0.21

39.3 0.63

40.4 9.15

212

i64

767

619

65

80

1,846

268

301

802

494

46

36

40.9

41.0

41.8

41.5

41.3

41.1

40.7

—

40.2

40.6

40.7

41.3

40.3

41.0

0.44

0.46

0.26

0.30

0.53

1.12

0.16

.

0.36

0.3B

0.15

0.24

0.50

1.07

1

200 42.2

240 42.5

746 42.7

587 42.9

100 43.5

67 42.5

1,90140.3

I

213 39.7

300 39.9

720 40.4

554 40.7

72 39.5

42 39.6

1

241 43.4

219 44.2

719 43.9

598 44.1

76 44.2

46 43.6

1,851 40.7

T

258 40,2

264 40.0

700 40.7

533 41.2

63 40.0

32 42.4

44.C 1.07 74

WL?2!hK

IT39.6 0.46 182

39.2 0.44 2@3

40.3 0,17 5s6

40.9 0.27 628

41.5 0.53 92

40.8 0.62 52

T6ble 14. 10th, 50th, and 90th percentiles of hemtmcritd istributionsfor youths byage8t Iastbirthday andsexfor the following

income groups: [essthan $4,0006 nd$lO,OOOOr more: United States, 1966-70

I I

Distribution at the IDistribution at the IDistribution at the

10th percentile 50th percentile 90th percentile

Age and sex

$10,000 ~ota, Less than $10,000

or more $4,000 or more

Less than

$4,000 Total

Male

12years . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . .

Female

12years . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . .

Hematocrit in ml percent

40.6 40.0

41.8 41.0

43.0 43.0

44.2 44.2

45.0 45.0

46.1 45.1

40.4 40.3

40.7 40.3

40.3 39.8

40.6 40.1

40.4 40.0

40.7 40.1

37.3

38.2

39.2

40.1

41.7

42.4

37.6

37.8

37.6

37.7

37.3

37.3

36.1

38.2

38.6

38.8

41.2

41.2

36.4

36.3

36.2

37.2

36.3

35.7

40.4

42.1

43.1

44.2

45.2

46.3

40.6

41.2

40.4

41.1

41.1

41.5

44.1

45.2

47.0

48.3

48.8

49.6

43.4

44.3

44.0

44.5

44.1

44.2

44.3

44.6

47.2

48.2

49.7

49.7

43.4

44.3

43,7

43.8

44.1

44.0

43.9

45.1

47.1

49.0

48.2

49.8

43.6

45.2

44.2

45.3

44.2

44.2

38.1

38.3

39.3

39.7

42.5

43.1

38.1

38.6

38.1

38.1

38.0

38.2

28
Table 15. Weighted sample size, mean hematocrits, andstindard errors of themeans foryouths, byage, sex, andeducation of parent: United States, lS66-70

12 years 13years 14 years 15 years 16 years 17 years

N x SE N x Sz N x Sz N x s% N z Sx N x Sx

SIN and education of parent

Total male Hematocrit in ml percent

All education groups

Lessthm 8 years . . . . . . . . .

&ll years . . . . . . . . . . . . . .

lzyl!ars . . . . . . . . . . . . . . .

13 years or mom . . . . . . . . .

Unknown . . . . . . . . . . . . . .

Total female

Alleducmlon groups . .

Lrss than .9 years . . . . . . . . .

S.llycms . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . .

13ymrs0rm0re . . . . . . . . .

Unknown . . . . . . . . . . . . . .

42.7 I 0.17 I 1,900 43.9 0.16

=

0.57

0.34

0.22

0.1s

0.90

0.16

=

0.36

0.19

0.21

0.35

1.28

2,0% 41.51 0.20 I 1,961 0.21 E!?_lJH

T

217 44.5

474 44.8

63o 44.8

480 45.1

36 45.7

1,789 40.4

0.21

—

0.60

0.25

0.24

0.37

0.58

0.18

—

0.56

0.28

0.18

0.36

1.5S3

X2i_!2!

T

20S 45.2

446 45.8

668 45.7

388 46.2

54 45.8

1,746 40.6

2,032

176

543

736

%2

16

1,970

211

460

729

509

41

40.51 0.17 —

1

39.7 0.48

40.0 0.26

40.8 0.22

40.9 0.31

39.6 6.96

40.3 0.17

T

39.4 0.46

40.2 0.26

40.5 0.21

40.7 0.18

39.4 0.56

175

502

780

627

23

1,946

228

507

727

463

22

41.1 0.75 172

41.2 0.28 474

41.7 0.24 730

41.4 0.38 549

41.6 0.71 196

42.8 0.2s 487

42.7 0.17 727

43.1 0.17 472

43.8

43.6

44.1

44.1

45.1

40.7

—

40.1

40.1

41.0

41.2

40.9

—

0.48

0.29

0.27

0.35

2.01

0.19

42.3 0.89 25 41.9 1.69 16

MINl_.W

lT40.1 0.69 160

40.4 0.24 537

40.9 0.17 719

41.3 0.24 465

,. 21

~

II39.6 0.56 176

40.1 0.26 596

40.5 0.23 640

40.5 0.34 411

39.1 1.38 22

—

1

167 39.7

463 39.7

623 40.6

512 40.9

34 40.7

146 39.7

465 40.6

525 40.8

542 40.8

67 39.6

0.69

0.23

0.22

0.32

9.29

—

Table 16. We[ghted sample size, mean hematocrits, andstandard errors of themeans forwhite youths, byage, sex, andannual family income: United States, 1966-70

Stw and annual f~mily income

12 years 13 years 14 years 15years 16 years 17 years

N x s% N x Sz N x SK N x Sx N z Sx N x Sz

White male

Al18nc0mes . . . . . . . .

Lcssthrm $3,000 . . . . . . . . .

83,000+4,999 . . . . . . . . . . .

$5,00C!-$9,999 . . . . . . . . . . .

$i0,0000rmOrc . . . . . . . . .

Don’t know . . . . . . . . . . . .

L31imkorrefuscd . . . . . . .

White female

Allincomcs . . . . . . . .

Ltssstht?n$3,000 . . . . . . . . .

$3,0QM4,999 . . . . . . . . . . .

$6,000$9,999 . . . . . . . . . . .

$l0,000ormOre . . . . . . . . .

Don’t know . . . . . . . . . . . .

81ank m refused . . . . . . . . .

Hematocrit in ml percent

42.9

.

42.3

42.7

42.8

43.0

43.7

42.8

40.4

40.0

40.2

40.4

40.7

39.7

39.7

0.19 I 1.546 44.1 0.25 1,594

T

43.6 0.54 129

44.6 0.60 211

44.0 0.32 632

44.1 0.24 501

44.4 0.38 67

43.6 0.94 55

!4J!2z

I

0.70 110

0.47 190

0.26 662

0.30 579

0.5+ 67

1.14 57

0.18 1,633

I

0.55 136

0.45 211

0.97 661

0.24 535

0.59 51

0.99 36

44.9 I 0.24 1,628

.

142

161

540

459

37

68

1,502

111

146

529

591

86

40

45.8

=

44.8

45.7

45.9

46.1

44.1

45.8

40.9

=

40.0

40.6

41.0

41.1

41.1

41.6

0.16

.

1.22

0.60

0.16

0.17

0.95

0.94

0.17

1,747

.

111

209

7s5

557

41

43

1,665

1s0

195

641

571

63

34

40.6

.

39.9

40.7

40.6

40.6

41.5

41.1

40.4

—

40.3

40.1

40.3

40.8

39.7

40.4

J’221JE

I

0.76 127

0.46 160

0.25 681

0.21 606

0.49 58

0.92 76

0.19 1,667

I

0,61 160

0.42 229

0.27 729

0.23 482

0.63 36

9.17 31

41.5

—

41.0

41.0

41.7

41.5

40.9

41.2

40.6 L

0.81 153

0.62 151

0.23 653

0.23 578

0.79 64

0.82 46

0.19 1,594

I

0,32 183

0.56 207

0.26 611

0.23 508

0.50 59

0.7.1 27

44.9 0.69

45.4 0.36

44.9 0.36

45.0 0.26

44.7 1.02

44.0 1.07

K!L?L40.7 0.17

lT40.1 0.62 155

40.5 0.41 113

40.9 0.27 569

41.3 0.25 571

40.0 0.72 69

40.5

40.6

40.7

41.3

40.6

40.6 — 1

40.5 0.44

39.7 0.63

40.5 0.19

41.0 0.22

41.8 0.52

41.2 0.57

0.6S

0.33

0.27

0.27

0.50

42.9 3.93 44 9.36

29
Table 17. Weighted sample size, mean hematocrits, and standard errors of the means for Negro youths, by age, sex, and annual family income: United States, 1‘%6-70

12 years 13 years 14 years 15 years 16 years 17 years

N x SF N x s~ N x SF N ~ SE N ~ SE N ~ Sz

Sex and annual family income

Negro male Hematocrit in ml percent

Al[ incomes . . . . . . . . .

Less than S3,ClXJ . . . . . . . . . .

$3,000$4,999 . . . . . . . . . . . .

$5,000-$9.999 . . . . . . . . . . .

$10,0CY30rmcie . . . . . . . . . .

Don’t know . . . . . . . . . . . . . .

Blank orrefused . . . . . . . . . . .

Negro female

All incomes . . . . . . . .

Less than $3,000 . . . . . . . . . .

$3,000$4,899 . . . . . . . . . . . .

$5,W$9,899 . . . . . . . . . . . .

$l0,0000rmOre . . . . . . . . . .

Don’t know . . . . . . . . . . . . . .

Blank orrefuwd . . . . . . . . . . .

41.7

42.1

41.7

41.8

39.6

42.0

.

39.4

39.1

39.1

40.5

40.0

39.0

●

—

0.27 [ 241 q

43.1

43.1

42.5

42.6

,

39.3

262 231 I 44.4

—

85

80

78

9

6

3

275

—

108

72

74

9

9

4

41.4

—

40.8

41.0

42.3

.

●

●

40.2

=

39.7

40.4

41.0

38.8

●

●

0.41

—

0.58

1.25

0.73

.

.

●

0.2s

=

0.57

1.00

0.65

2.37

●

●

—

256 0.32

=

0.9B

0.68

0.75

2.10

●

0.39

=

0.70

0.69

0.71

2.12

●

●

0.43

—

1.05

0.77

1.18

.

.

0.47

=

0.90

0.75

0.49

2.32

1.51

,

226

=

85

58

48

17

12

6

237

=

71

6C

58

3C

6

12

45.7

=

46,0

44.3

46,7

46.7

45.7

.

38.5

—

390

37,2

379

41.7

.

37.7

047

=

0.53

12!3

0.92

0.57

1029

●

050

=

0.60

128

0.67

1.76

●

1.23

280

—

69

96

81

16

14

2

272

=

77

75

81

19

16

4

39.6

39.6

39.0

40.4

40.3

39.2

●

39.7

40.0

39.5

40.1

39.0

●

●

0.35

0.39

0.53

0.76

0.73

9.24

●

0.21

0.62

0.48

0.27

0.56

.

●

0.66

0.72

0.92

0.64

1.84

.

88

65

59

17

12

89

50

78

15

13

11

266 1

72 44.0

54 43.9

80 44.7

10 ‘

15 “

. .

243 38.3

T

69 37.8

52 38.1

57 38.7

23 38.0

14 40.0

7’

0.47 235

75

89

57

19

21

6

0.63 75

1.13 52

0.90 81

1.76 1?

0.62

● E

40.4

38.4

39.3

37.1

.

●

Table 18. Weighted sample size, mean hematocrits, and standard errors of the means for white youths, by age. sex, and education of parent: United States, 1966-70

12 years 13 years 14 years 15 years 16 years 17 years

N x 5X N z .x N x s~ N x s~ N z s~ N z s~

Sex and education of parent

White male

All educat,on groups .

Lessthan 8years . . . . . . . .

f$ll years . . . . . . . . . . . . . .

12 years . . . . . . . . . . . . . . .

13years0rm0re . . .

Unknown . . . . . . . . . . . . .

Hematocrit in ml pwcent

0.21 I 1,685 I 42,9

T

1.20 145 41.8

0.30 341 42.9

0.23 662 42,9

0.40 623 43.1

0.95 14 43.6

0.19

=

0.83

0.35

0.17

0.16

9.98

0.19

1,646

139

380

652

461

14

1,5s4

127

479

578

391

20

3!-I-E3

T

43.8 0.62

43.9 0.35

44.1 0.32

44.2 0.33

46.5 1.64

40.9 0.18

*

T

45.1 0.63

44.7 0.28

44.8 0.24

45.1 0.40

45.6 0.67

40.7 0.17

E_13?

I

119 40.1

412 40.1

675 40.8

526 41.0

13 “

1,685 40.4

I

165 39.7

379 40.3

650 40.6

464 40.6

26 39.5

0.19

=

0.76

0.28

0.23

0.32

.

0.19

=

0.85

0.32

0.24

0.19

0.55

—

1,729

104

39t

713

501

19

1,667

182

356

561

452

16

41.5

—

41.1

41.4

4t.6

41.4

42.2

40.8

=

40.3

40.3

41.0

41.3

.

1.584

169

371

5s0

446

28

1,642

1,528

143

342

632

363

49

1,502

45.8

—

45.1

458

45.8

46.2

45.7

40.9

=

40.5

41.1

41.0

41.1

39.3

0.16

=

0.79

0.37

0.22

0.18

0.99

0.17

White female

All education groups 0.18 I 1,633 I 40.4

Lessthan 8 years . . . . . . .

Ell years . . . . . . . . . . . .

12years . . . . . . . . . . . . .

13years0rm0re . . . . . . .

Unknown, . . . . . . . . . . .

1.01 107 39.5

0.33 429 40.2

0.17 648 40.6

0.24 440 40.7

●

9 “

0.83

0.32

0.24

0.28

.

40.0 0.93

40.4 0.21

41.2 0.25

41.3 0.33

41.1 9.38

106

349

672

490

24

40.8 0.65

40.2 0.3+7

40.6 0.18

41.1 0.28

41.3 1.63

96

344

481

516

55

0.75

0.24

0.21

0.34

1.67

30
Table 19. Weighted sample stze, mean hematocrits, and standard errors of the means for Negro youths, by age, sex, and education of parent: United States, 1966-70

SW and cducaticm of parent

12 years 1 13 years I 14 years I 15 years I 16 vears 17 vears

Negro knde Hematocrit in ml percent

All t?ducatinn groups . . . .

Lmsthan8yaws . . . . . . . . . . .

,%llyuars . . . . . . . . . . . . . . . .

12ycws . . . . . . . . . . . . . . . . .

13 vticwsw more . . . . . . . . . . .

Unhrmwn. . . . . . . . . . . . . . . .

Neqru female

All educatitm groups . . . .

Lwsthan8vears . . . . . . . . . . .

S. Ilvmrs . . . . . . . . . . . . . . . .

12yews . . . . . . . . . . . . . . . . .

13yimrs0rm0re . . . . . . . . . . .

(.hknown . . . . . . . . . . . . . . . .

41.8

40.6

42.5

40.9

42.4

*

39.4

39.6

39.6

40.1

37.4

●

0.27

9.28

0.45

0.48

1.13

,

0.46

0.82

0.59

0.64

3.06

●

N-135

I

57 43.5

103 42.4

69 43.8

8“

3“

235 39.3

I

47 40.6

109 39.0

63 39.0

14 39.3

3’

28o I 39.7 0.35

II

57 38.9 0.44

130 39.7 0.60

68 40.6 0.44

32 39.1 1.18

3*”

272 39.7 0.21

*

I

41.2 1.32

40.7 0.72

41.9 1.00

43.5 0.98

.*

40.3 0.29

I

39.4 0.92

40.4 0.54

40.6 0.56

**

● .

*

T

42.4 1.29

45.2 0.64

44.4 0.81

44.6 0.62

,.

38.3 0.47

fz-u!cE

T

46.5 0.62

45.7 0.84

44.9 1.17

47.0 0.78

. .

38.5 0.50

262

—

71

102

64

23

3

275

—

46

147

65

11

5

256

27

130

68

20

11

266

53

1C6

71

25

12

—

&-1-2

T

0.67 48

0.66 103

0.73 46

.

27

.

7

0.39 243

225

—

62

104

31

23

6

237

—

50

117

35

24

12

38.o 0.77

39.2 0.63

38.9 1.13

35.2 1.32

40.5 9.08

46 38.5

96 39.7

79 39.8

35 41.3

15 39.1

0.64

0.31

0.29

0.39

1,01

0.96 61

0.64 104

0.78 50

0.40 18

●

10 1

37.6 0.95

38.0 0.43

40.2 0.56

● *

. .

Table 20. Mean hematocrit by age and sex for HES Cycle I I I and Cycle I data

Midpoint of

age interval

12.5

13.5

14.5

15.5

16.5

17.5

21.5

30

40

50

60

70

77.5

Male Female

Mean hamatocrit

in ml percent

40.5

41.5

42.7

43.9

44.9

45.8

46.7

47.0

46.6

46.5

46.1

45.8

45.1

Estimated

increase per year

in ml percent

1.0

1.2

1.2

1.0

0.9

0.2

0.04

-0.04

-0.01

-0.04

-0.03

-0.07

Mean hematocrit

in ml percent

40.3

40.8

40.3

40.7

40.4

40.6

41.4

41.8

42.0

42.5

43.7

43.2

43.1

Estimated

ncrease per year

in ml percent

0.5

-0.5

0.4

-0.3

0.2

0.2

0.05

0.02

0.05

0.12

-0.05

-0.01

Cycle

Cycle Ill

Cycle I

Age group

12 . . ! . . . . . . . . . . . . .

13. .’ . . . . . . . . ...4..

14 . . . . . . . . . . . . . . . .

15 . . . . . . .. . . . . . . . . .

16 . . . . . . . . . . . . . . . .

17 . . . . . . . . . . . . . . . .

18-24 .. . . . . . . . . . . . .

26-34 . . . . . . . . . . . . . .

35-44 . . . . . . . . . . . . . .

45-5 $. . . . . . . . . . . . . .

55-64 . . . . . . . . . . . . . .

65-74 .. . . . . . . . . . . . .

75-79’ . . . . . . . . . . . . . .

31
APPENDIX I

STATISTICAL NOTES

The Survey Design

The sampling plan of Cycle III of the Health

Examination Survey followed a multistage,

stratified probability sample of clusters of

households in Iand-based segments in which a

sample of the U.S. population (including Alaska

and Hawaii ) aged 12 through 17 years was

selected. Excluded were those youths confined

to institutions and those residing on any of the

reservation lands set aside for use by American

Indians.

The sample design of Cycle III is similar to

that of Cycle II in that it uses the same 40

sample areas and the same segments. The decision to incorporate this feature into Cycle III

was not made prior to the selection of the Cycle

II sample, although it is consistent with the early

concept of a single program for persons 6-17

years old. The final decision to use this identical

sampling frame was made during the operation

of the Cycle II program.

The successive elements for this sample design

are primary sampling unit; census enumeration

district; segment (a cluster of househoMs);

household; all eligible youths; and finally, the

sample youth. Every eligible youth within the

defined population has a known and approximately equaI chance for selection into the

sample.

The steps of drawing the sample were carried

out jointly with the U.S. Bureau of the Census;

the starting points were the 1960 decennial

census lists of addresses and the nearly 1,900

primary sampling units (PSU’S) into which the

entire United States was divided. Each PSU is a

standard metropolitan statistical area (SMSA), a

county, or a group of two or three contiguous

counties. These PSU’S were grouped into 40

strata so that each stratum had an average size of

about 4.5 million persons. This grouping was

done in a manner which maximized the degree

of homogeneity within strata with regard to the

population size of the PSU’S, degree of urbanization, geographic proximity, and degree of industriaIization. The 40 strata were then classified into four broad geo~aphic regions of 10

strata each and, within each region, cross-classified by four population density classes and by

the rates of population change from 1950 to

1960. Using a modified Goodman-Kish controlled-selection technique, one PSU was drawn

from each of the 40 strata.

The sampling within PSU’S was carried out in

several steps. The first was the selection of

census enumeration districts (ED’s). These ED’s

are small well-defined areas of about 250 housing units into which the entire Nation was

divided for the 1960 population census. Each

ED was assigned a “measure of size” equal to

the rounded whole number resulting from a

“division by nine” of the number of children

aged 5-9 in the ED at the time of the 1960

census. A sample of 20 ED’s in the sample PSU

was selected according to a systematic sampling

technique with each ED having a probability of

selection proportional to the population of

children 5-9 years at the time of the 1960 census

date. From each ED a random selection of one

measure of size (segment) was taken.

Minor changes required in the Cycle HI design

were that it be supplemented for new construction to a greater extent than had been necessary

in Cycle II and that reserve segments be added.

Although it was the plan for Cycle III to use the

Cycle II segments, it was recognized that within

several PSU’S additiomd reserve segments would

be needed to avoid the risk of having an

insufficient number of examinees. This was

prompted by the fact that four of the PSU’S in

32
Cycle H had yields of less than 165 eligible

children and several others were marginal in

their yield. In addition, there was a 3-Year

inkrval between Cycle II and Cycle III, so that

it was quite possible for some segments to have

been completely demolished to make room for

highway construction or urban redevelopment.

The time available for examinations at a

particular location or stand, as they have been

designated, is necessarily set far in advance of

any preliminary field work at the stand. Therefore, the number of examinations that can be

performed at a particular location is dependent

on the number of examining days available. At

the majority of locations, the number of days

mnilable, excluding Saturdays, is 17. At the rate

of 12 examinations each day, this provides for

~0~ examination slots. Exam~ations are con.

ducted on Saturdays if, for some reason, it is

necessary. Because of rescheduling for cancellations or no-shows, the maximum number of

youths that is considered for inclusion in the

mmple is 200. When the number of eligible

youths exceeds this number, subsampling is

performed to reduce the number to manageable

limits. This is accomplished through the use of,a

master list, which is a listing of all eligible

youths in order by segment, serial number

(household order within segment), and column

number (order in the household by age). After

the subsampling rate has been determined, every

nth name on the list is deleted, starting with the

yth name, y being a randomly selected number

between 1 and n. Youths who are deleted from

the Cycle III sampIe bbt who were examined in

Cycle 11 as well as any twin who may have been

deleted are, if time permits, scheduled for an

examination for inclusion only in the longitudinal study portign or twin study portion of the

survey. Their data are not included in the report

as part of the regular sample.

Since the strata are roughly equal in population size and a nearly equal number of sample

youths were examined in each of the sample

PSU’S, the sample design is essentially, selfweighting with respect to the target population;

that is, each youth 12 through 17 years old had

about the same probability of being drawn into

the sample.

The adjustment upward for nonresponse is

intended to minimize the impact of nonresponse

on final estimates by imputing to nonrespondents the characteristics of “similar” respondents. Here “similar” respondents were judged

to be examined youths in a sample PSU having

the same age (in years) and sex as those not

examined in that sample PSU.

The poststratified ratio adjustment used in

Cycle HI achieved most of the gains in precision

that would have been attained if the sample had

been drawn from a population stratified by age,

color, and sex, and it made the final sample

estimates of population a~ee exactly with independent controls prepared by the U.S. Bureau

of the Census for the noninstitutional population of the United States as of March 9, 1968

(approximaate midsurvey point), by color and

sex for each single year of age 12 through 17.

The weight of every responding sample child in

each of the 24 age, race, and sex classes is

adjusted upward or downward so that the

weighted total within the class equals the independent population control.

A more detailed description of the sampling

plan and estimation procedures is included in

Vital and Health Statistics, Series 2, Number

43,3s and in Series 1, Numbers 1,1 5,s and 8,4

which describe the plan and operation of the

first three cycles of the Health Examination

Survey (HES).

Some Notes on Response Rates

As mentioned previously, the sample designs

of the second and third cycles of the HES were

similar. Differences did occur, however, in response rates of various subgroups of these

samples, and these differences deserve some

consideration here.

Most importantly, the number of youths

selected for examination increased from 7,417

in Cycle II to 7,514 in Cycle III. The response

rate, that is, the number of youths selected who

were actually examined, decreased horn 96

percent in Cycle II to 90 percent in Cycle III.Of

the examined youths of Cycle II, 13.9 percent

were Negro compared with 14.8 percent of

those examined in Cycle III. This difference

does not reflect a difference in the percentage of

Negro youths selected for examination, but

instead, a smaller decrease in response rate for

33
Negro youths between the two cycles than was

the case for the white youths. In actuality, 13.8

percent of the sample selected for examination

was Negro in Cycle III corresponding to 13.5

percent for Cycle II. However, whereas the

response rate for white youths dropped from

95.6 percent in Cycle II to 89.1 percent in Cycle

III, the response rate for Negro youths dropped

a far lesser degree from 98.4 percent to 96.6

percent. Thus, better relative response from the

Negro portion of the sample yielded a greater

percentage of these youths actually examined

during Cycle 111 than was the case during the

previous sample.

Examination of sample sizes in this report

clearly shows that at every age group there were

fewer females actually examined than there were

males of the same age. This again is not

attributed to differences in numbers of youths

selected in the sampling design, but rather to the

following differential response rates between

males and females:

Age Male Female

Total . . . . . . . . . . . . . . . . . . . . . . . 91.4 88.7

12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.5 91.3

13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2 91.9

14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.7 90.7

15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.6 87.9

16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89.8 87.7

17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87.6 81.8

Note that at each age group the response rate for

males exceeded that for females.

A similar analysis of response rates can be

done by age, race, and sex as foIlows:

Age

White Negro White Negro

male male female female

Total . . . . . . . . . 90.5 87.6 87.4 95.8

12 . . . . . . . . . . . . . . . 92.6 99.0 90.1 98.9

13 . . . . . . . . . . . . . . . 92.5 98.8 91.1 96.8

14 . . . . . . . . . . . . . . . 91.0 87.8 89.6 96.2

15 . . . . . . . . . . . . . . . 90.7 97.7 86.4 98.6

16 . . . . . . . . . . . . . . . 89.2 95.0 86.6 93.0

17 . . . . . . . . . . . . . . . 86.5 95.8 80.2 91.4

The above clearly indicates that for all ages

under consideration in Cycle 111 of the HES the

response rate for Negro youths exceeded that

for white youths of the same sex and age.

Reasons for differences in response rates are

many, but may range from the incentive to get

examined in order to miss a day of school, to

fear of the examination itself, to inhibitions

with respect to being examined. The worst

response rate was recorded for the oldest females, that is, those aged 17 years.

Parameter and Variance Estimates

Because each of the 6,768 sample children has

an assigned statistical weight, all estimates of

population parameters presented in HES publications are computed taking this weight into

consideration. Thus, ~, the estimate of a population mean, “P,” is computed as follows:

where Xi is the observation or measurement

taken on the ith person and Wi is the statistical

weight assigned to that person.

The HES has an extremely complex sampling

plan, and obviously the estimation procedure is,

by the very nature of the sample, complex as

well. A method is required for estimating the

reliability of findings that “reflects both the

losses from clustering sample cases at two stages

and the gains from stratification, ratio estimation, and poststratification. “s A

The method for estimating variances in the

HES is the half-sample replication technique.

The method was developed at the U.S. Bureau

of the Census prior to 1957 and has at times

been given limited use in the estimation of the

reliability of results from the Current Population

Survey. This half-sample replication technique is

particularly well suited to the HES because the

sample, although complex in design, is relatively

small (6,768 cases) and is based on but 40 strata.

This feature permitted the development of a

variance estimation computer program that produces tables containing desired estimates of

aggregates, means, or distributions, together

with a table identical in format but that contains

the estimated variance of the estimated statistics. The computations required by the method

are simple, and the internal storage requirements

are well within the limitation of the IBM 360-50

computer system used at the National Center for

Health Statistics.

34
Variance estimates computed for this report

were based on 20 balanced half-sample replications. A half sample was formed by choosing

one sample PSU from each of 20 pairs of sample

PSU’S. The composition of the 20 half samples

was determined by an orthogonal plan. To

compute the variance of any statistic, this

statistic is computed for each of the 20 half

samples. Using the mean as an example, this is

denoted .~i. Then, the wefihted mean of the

entire, undivided sample (~) is computed. The

variance of the mean is the mean square deviation of each of the% half-sample means about

the overall mean. Symbolically,

.fl(Xi- X)2

Var(X) = Z.

and the standard error of the mean is the square

root of this. In a similar manner, the standard

error of any statistic may be computed.

A detailed description of this replication

process has been published in Vital and Health

Statistics, Series 2, Number 14.35

Standards of Reliability and Precision

All means, variances, and percentages appearing in this report met defined standards before

they were considered acceptably precise and

reliable.

The rule for reporting means and percentiles

consisted of two basic criteria. The first criterion

WJS that a sample size of at least five was

required. If this first criterion was met, then the

second criterion, that the estimated coefficient

of variation [i.e., the standard error of the mean

divided by the mean (sx/X)] was to be less than

~J percent, must have been demonstrated. Thus>

if either the sample size was too small, or the

variation with respect to the mean was too large,

the estimate was considered neither precise nor

reliable enough to meet the standards established for publication.

To illustrate these criteria, in table 17 values

of the mean and standard error for 16-year-old

Negro males from families with a total yearly

income of $10,000 or more were replaced by

asterisks (*) since the standard error with

respect to the mean exceeded the criterion

previously stated.

Imputation

In addition to the subject nonresponse discussed previously, the problem of item nonresponse merits consideration here. In this situation, information about a respondent is complete with the exception of a missing hematocrit

value.

Missing data and values that fell outside a

normal range and were deemed unlikely after

examination of physician records were replaced

by the value recorded for a randomly selected

respondent of similar age, sex, and race. However, when only one of the two hematocrit

values was missing, the recorded measurement

was substituted for the unknown value. Imputation, where there was no value recorded for

examinees, was necessary in 190 cases for

hematocrits (2.9 percent of total respondents).

In effect, sample cases were sorted into

categories within each of which the cases were

expected to have high intraclass correlation (i.e.,

being relatively homogeneous). Those with missing values were then completed with a value

randomly selected from within the category.

This method of imputation preserves both the

expected values and the distribution of values in

each category to those of the respondent cases.

35
APPENDIX II

DEMOGRAPHIC VARIABLES

(

Regional and demo.qaphic characteristics by

whic~ the population ~as-been classified for tti-s

report are defined as follows.

Age and sex. –Population was classified into

12 age-sex groups-the six ages 12-17 years by

sex. Birth certificates were obtainable for verification of age for 92 percent of the youths. Age

stated by the parents was accepted as the true

age for the other 8 percent. Age is expressed as

years attained at last birthday.

Race. –Hematocrit was reported by race for

white and Negro youths. Youths of other races

were not sampled sufficiently for comparison

purposes; these youths represented only 0.55

percent of the sample.

Region. –Regional data are presented for four

regions of the continental United States.

Region States Included

Northeast . . . Maine, Vermont, New Hampshire, Massachusetts, Rhode

Island, Connecticut, New

York, Pennsylvania, New Jersey

Midwest . . . . Minnesota, Wisconsin, Michigan, Iowa, Missouri, Illinois,

Indiana, Ohio

South . . . . . . Delaware, Maryland, Virginia,

District of Columbia, West

V@inia, Kentucky, Tennessee, North Carolina, South

Carolina, Georgia, Florida,

Alabama, Mississippi, Arkansas, Louisiana

West . . . . . . . Washington, Oregon, Idaho,

Montana, North Dakota,

South Dakota, Wyoming,

Nebraska, Kansas, Colorado,

Utah, Nevada, California, Arizona, New Mexico, Texas,

Oklahoma, Alaska, Hawaii

Family income. –The income recorded was

the total income received during the past 12

months by the head of the household and all

other household members related to the head by

blood, marriage, or adoption. This income was

the gross cash income (excluding pay in kind)

except in the case of a family with its own farm

or business, in which case net income was

recorded.

Education of paren t or guardian. –This item

was recorded as the highest grade that had been

completed in school. The only grades counted

were those that had been completed in a regular

school in which persons were given formal

education in graded or private schools, either

day or night schools , with either full-time or

part-time attendance. A “regular” school is one

that advances a person toward an elementary or

high school diploma, or a college, university, or

professional school degree. Education in vocational, trade, or business schools outside the

regular school system was not counted in determining the highest grade of school completed.

36
APPENDIX Ill

TECHNIQUES OF MEASUREMENT AND QUALITY CONTROL

Measurement

The HES blood-drawing technique and its

historical development. –For a variety of reasons, it was decided not to attempt to draw a

blood specimen on children 6-11 years of age in

Cycle II. The children included in the national

probability sample came from all regions of the

country and all cultural and socioeconomic

groupings and ways of life; some would never

have been to a physician before; some would

have had very bad memories and associations. In

addition, by sampling the entire spectrum of

behavioral and physical development extant in

the United States, some of the 6-year-old children and even some of the 7-year-old children

would be so immature as to present severe

technical and behavioral problems. It was believed that fear, or extreme distaste, of having a

blood sample drawn felt by many potential

subjects might severely affeet the response rate,

which is so crucial to a survey like this. When it

is remembered that the overall response rate for

Cycle II was a remarkable 96 percent, it is

difficult to argue with that line of reasoning. Of

course, now it can never be known how great a

diminution of the response rate the addition of a

blood sample would have caused.

In the early planning stages of Cycle III, it

was decided to obtain a blood specimen if at all

feasible, that is, primarily if the price in diminished response rate and cooperation of the

wmminees would not be too high. Accordingly,

in three separate pretests, investigations were

conducted regarding the problem of developing

a satisfactory blood-collection technique for this

age ~group and examination setting. The optimum amount of blood drawn that would not

have an emotional impact on the examinee and

would not affect his performance in any of the

procedures to follow was desired. The amount

of usable blood that could be drawn posed a

limiting factor on the number of blood chemistry tests that could be performed and made a

difference in accepting or rejecting an entire

possible area of the examination such as the

nutritional assessment. Logistical problems also

had to be resolved involving the handling,

separating, and packaging of drawn blood so

that there would be a minimum of blood loss

and packaging error. For the refrigerated but

unfrozen bloods, time from shipment to delivery

was critical; therefore, arrangements had to be

made with postal authorities to assure prompt

delivery to the laboratories in order to avoid

spoi~age.

There was a trial-and-error process, and there

was good advice and help from many sources in

developing a satisfactory blood-drawing technique. The chief sources of help, outside of the

immediate HES technical staff, were Dr. Wi~a

Bias and Dr. Bernice Cohen of The Johns

Hopkins University; Dr. Gerald Cooper, Chief of

Laboratories, Communicable Disease Center,

Public Health Service, Atlanta, Georgia; the

many teenage subjects during our pretest who

gave valuable suggestions and who pointed out,

either as overt advice or by their immediate

reactions, specific points to be avoided; and,

finally, the professional and technical division of

the Becton-Dickinson Company, Rutherford,

New Jersey. The latter, through several personal

visits by a representative of their technical

division, not only gave excellent technical advice

on blood-collection techniques and the use of

alternative equipment but also devised a special

fitting that made the transfer from one vacutainer tube to another much smoother.

During the pretesting, it was learned that

many subjects did not like to see any part of the

37
blood-drawing procedure, including their own

blood in tubes. Therefore, a technique was

employed that minimized the subject’s attention

to the operation. With the subject lying supine

and by draping and by keeping the arm and

tubes well below the level of the examination

table, effective screening was achieved. After the

skin area was cleansed with alcohol, the blood

was then drawn from the antecubital fossa by

the physician-nurse team. At the discretion of

the physician, a tourniquet was used to fill the

vein; however, once the needle was inserted into

the vein, the tourniquet was taken off the arm

so that the blood flowed freely.

A B-D blood culture needle and tube were

used to draw blood. Using the specially prepared

link fitting, the nurse inserted the short needle

into a vacutainer tube holder. The tube was

clamped with a hemostat until the vein was

punctured and the vacutainer inserted into the

holder.

From the one free-flowing venipuncture, a

total of only 55 cms of blood was collected in

foLIr separate vacutainer tubes from all male and

almost half of the female subjects. (The difference being that all males had separate plasma

drawn to be frozen “and stored for future

testosterone determination and almost half of

the females provided a replicate blood specimen

for quality control of the laboratory determinations; the remaining females had 40 cm3 drawn.)

All test tubes were labeled with the examinee’s number and left in the test-tube holding

rack at room temperature for 1 hour. The nurse

then placed the tubes in the laboratory

refrigerator, along with 10 extra examinee identification labels, for the technicians.

An analysis that attempts to estimate the

impact of the addition of a blood sample on the

Cycle III sample response rate is in progress.

Hematocrit determinations. –After the B-D

blood culture needle set was withdrawn from

the arm, the tube was drained; and the two

microcapillary tubes were two-thirds filled with

the residual blood in the tubing. They were

sealed with Sealease and centrifuged (International Model MB) for 5 minutes. Both specimens

were read to the nearest percent directly from

an International Micri-capillary Reader, Model

CR.

The mean of the two readings expressed as

the volume (in milliliters) occupied by the red

cells per 100 milliliters of whole blood was

recorded as the subject’s hematocrit value.

Monitoring Systems

In addition to the sampling considerations

already discussed, the quality of data collected is

also a special concern. One of the main purposes

of the monitoring system employed in the

survey was to indicate whether the measurements produced by our measurement process

attained the desired quality. A second major

purpose was to make possible quantitative summary descriptions of residual measurement

errors to aid in the interpretation of survey data.

The monitoring system as applied to the

taking of blood samples consisted of a formal

system of replicate examinations (described later

in this appendix). Replicate measurements are

useful for a variety of reasons, for example, as a

means of increasing precision of estimates of

individual measurements, as a training technique, and as a monitoring system that includes

the objective of overaIl evaluation of measurement errors. These objectives are not incompatible, and replicate data collected primarily

for one of these objectives often indirectly, if

not directly, accomplish one or both of the

remaining two. For this reason, replicate data

are most often collected with a combination of

these objectives in mind.

Methods of Taking Replicate Measurements

A major source of uncertainty in estimates

derived from replicate measurements is in the

inability to make the replicate measurement

under precisely the’ same conditions and in the

same manner as the original measurement. This

uncertain y is difficult to evaluate, and most

attempts are restricted to subjective statements

concerning the direction and/or size of the bias

and the need for concern in the analysis of data.

Each sample examinee had blood drawn into

two microhematocrit tubes, and readings were

obtained by the same technician according to

the procedure described previously. Since the

two blood samples were taken at the same time,

diurnal variation in the hematocrit of the examinee would not be expected to be a source of

3a
variation bet ween the two readings. It is possible

that differences may have occurred between the

two specimens in duration of time centrifuged

and in the time interval between the drawing

and centrifuging of the blood sample. However,

these differences were held within strict limits,

and it is unlikely that they are a major source of

variation between the two readings. The most

important source of variation between the two

readings by the same technician is likely to be a

reading error. Part of the reading error is due to

a “rounding error “ in the last significant figure,

since readings were taken to the nearest percent.

Since the hematocrit value reported in the

survey is an average of the duplicate readings by

the same technician, the effect of rounding error

would tend to be ameliorated. In the following

analysis, the differences between the two readings by the same technician will be referred to as

“intraobserver” differences.

A study was undertaken to evaluate the

extent of variation between two observers reading the same microhematocrit tube. This was

done by having a supervisory technician on

Monday mornings read the hematocrits for the

morning and enter the findings beside the

originals. In the ensuing discussions, such differences will be referred to as “interobserver”

differences.

Results of the Replicate Studies for

Hematocrit

Two hematocrit readings were obtained by

the same technician on 6,375 examinees (94.2

percent of the total sample). Replicate readings

by another technician were obtained on 640

examinees (9.5 percent of the total sample) for a

total of 1,280 replicate measures. All together,

during the 4 years, 12 technicians participated in

obtaining replicate measurements for this phase

of the quality control progam.

Since there were 12 technicians employed

during Cycle III, it is of interest to ascertain

whether each of the examiners had a representative number of replicate measurement sessions

with respect to the number of examinations

performed during the survey. It should be

carefully noted that it was not possible to insure

that each technician had equal chances to

perform replicate measures, since the length of

time various technicians associated with the

survey team varied.

Table I presents the percentage of total

examinations done in the survey, the percentage

of intraexaminer replicates, and the percentage

of interexaminer replicates participated in by

each of the 12 technicians. Table I indicates

some possible sources of bias that may affect the

Table 1. Percent of regular Cycle III hematocrit examinations and replicate hematocrit examinations participated in

by each technician

Technician number

1 . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 .,, .,... . . . . . . . . . . . . . . . . . . .

3 .,, ..,,. . . . . . . . . . . . . . . . . . . .

4 . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 . . . . . . . . . . . . . . . . . . . . . . . . . . .

7 ,, .,,,., . . . . . . . . . . . . . . . . . . .

8 . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 . . . . . . . . . . . . . . . . . . . . . . . . . . .

lo . . . . . . . . . . . . . . . . . . . . . . . . . .

11, . . . . . . . . . . . . . . . . . . . . . . . . .

12 . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent of regular

Cycle I I I examinations

0.1

13.7

25.8

7.2

13.9

4.3

3.7

12.6

13.5

0.0

4.2

1.0

Percent of replicate examinations

Intraobserver

0.0

13.9

25.8

7.1

14.0

4.2

3.6

12.8

13.4

0.0

4.2

1.0

Interobsetver

15.8

9.4

35.6

1.7

10.7

4.1

2.2

7.5

9.0

2.3

1.8

39
analysis of replicate data. The number of interexaminer replicate examinations is distributed

between technicians disproportionately with

respect to regular and intraexaminer replicate

readings. For example, assume technician 3 was

in very close agreement on his own readings, but

his readings were very different from the other

examiners’. Because of this technician’s overrepresentation, the distribution of interexaminer

differences would be considerably more skewed

than it should have, since the technician does

not agree well with the other technicians’

measurements. Thus, the various combinations

of observers for the interexaminer replicates and

the proportions of intraexaminer replicates were

not controlled so as to be balanced among the

observers. In the survey proper, the examinations were similarly not (of necessity, since

length of time the various technicians were

associated with the survey varied) proportionately distributed among the observers.

The foregoing indicates that the distribution

of numbers of replicate examinations done by

each technician is not the same as the distribution of the total number of survey examinations

done by each in Cycle III. This represents one of

the inherent problems of the present replicate

data, and, limits to some extent implications to

the survey as a whole. Nevertheless, the reader

should be aware of the many problems confronting those who conduct large-scale health surveys,a 6 and in this context, the present systematic approach to the collection of replicate data is

adequate.

For both the intraobserver study and the

interobserver study, frequency distributions of

the absolute differences between replicate

hematocrit readings are presented in table II.

As a summary statistic of the distribution of

differences between replicate hematocrit readings displayed in table H, we have computed

V–the percentage technical error of m&surement—which is given by

I

where

n is the number of pairs of measurements in

the study,

Table 11. Frequency and percent distribution of absolute differences between replicates for the interobserver and intraobserver studies of hematocrit measurement error

Absolute

difference

(in milliliters)

Total . .

0 . . . . . . . . .

1 . . . . . . . . .

2 . . . . . . . . .

3 . . . . . . . . .

4 . . . . . . . . .

5 . . . . . . . . .

6 . . . . . . . . .

7 . . . . . . . . .

8 . . . . . . . . .

9 . . . . . . . . .

lo . . . . . . . .

11 . . . . . . . .

1nterobserver study

Frequency

1,280

732

544

4

0

0

0

0

0

0

0

0

0

Percent

of total

100.0

57.2

42.5

0.3

Intraobserver study

Frequency

6,375

3,858

2,488

16

6

2

3

0

0

1

0

0

1

‘ercen t

>f total

100.0

60.5

39.0

0.2

0.1

0.1

df is the square of the difference between

members of the ith pair of measurements

(i= 1,.. .,n), and

~ is the arithmetic mean of the 2n measurements in the study.

The percentage technical error, V, can be interpreted as a “coefficient of variation” and is a

dimensionless constant. It essentially describes

the size of measurement error relative to the

mean value of a measurement. For replicate

hematocrit determinations obtained in the interobserver and intraobserver studies, the values of

V are the following:

Study

Interobserver

Intraobserver

The interpretation

two observers reading

v

1.12 percent

1.14 percent

of these statistics is that

the same microhematocrit

tube would, on the _-average, record values that

differ from each other by about 1 percent.

Likewise, a single technician reading two microhematocrit tubes obtained from a single venipuncture processed under identical laboratory

conditions would record values that differ from

each other by an average of approximately 1

percent.

40 .
Sm”es 1.

Sm”es 2.

Sm’es 3.

Series 4.

Series 10.

Sera”es 11.

Series 12.

Sm”es 13.

Series 14.

Sm”es 20.

Sw”es 21.

Series 22.

*

VITAL AND HEALTH STATISTICS PUBLICATION SERIES

Formerly public Health SetvicepublicationNo. 1000

Pngmms and collection Procedures. - Reports which describe the general programs of the National

Center for Health Statistics and its offices and dfvisions, data collection methods used, defioftions,

and other material necessary for understanding the data.

Lkzta eualwxtion and methods research. —Studies of new statistical methcxfology inclu~ experimental testa of new survey methods, studfes of vital statistics collqdon methods, new snaiytfcal

techniques”, objective evaluations of reliability of collected data, contributions to statistical theory.

/

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