Data from the

NATIONAL HEALTH SURVEY

Serum Uric Acid Values

Of Youths 12-17 Years

UnitedStates

Serum uric acid values are presented and discussed by age, sex,

race, and socioeconomic level of youths 12-17 years of age in the

United States, 1966-70.

DHEW Publication No. (H RA) 76-1634

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

Public Health Service

Series 11

Number 152

Health Resources Administration

National Center for Health Statistics

Rockville, Md. August 1975
Library of Congress Cataloging in Publication Data

Levy, Paul S.

Serum uric acid values of youths 12-17 years, United States.

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

no. 152) (DHEW publication no. (HRA) 76-1 634)

Includes bibliographical references.

Supt. of Dots no.: HE 20.6209:11/152

1. Youth–Health and hygiene-United States–Statistics, Medical. 2. Uric acid.

3. Blood–AnaIysis and chemistry. I. Hamill, Peter V. V., joint author. II. Heald, Felix, joint

author. III. Rowland, Michael, joint author. IV. United States. National Center for Health

Statistics. 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. 152. VI. Series: United States. Dept. of Health, Education and

Welfare. DHEW publication no. (HRA) 76-1634.

RA407.3.A347 no. 152 [RA564.5] 312’.0973s [312’.6]

ISBN 0-8406-0041-0 75-619039

For sale by the Superintendent of Documents, U.S. (loverrrrnent Printing Office, Washington, D.C. 2M02- Price 85 writs

—
NATIONAL CENTER FOR HEALTH STATISTICS

EDWARD B. PERRIN, Ph.D., Director

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

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

ELIJAH L. WHITE, Associate Director for Data Systems

IWAO M. MORIYAMA, Ph.D., Associate Director for International S tatistics

EDWARD E. MINTY, Associate Director for Management

ROBERT A. ISRAEL, Associate Director for Operations

QUENTIN R. REMEIN, Associate Director for Program Development

ALICE HAYWOOD, Information Officer

DIVISION OF HEALTH EXAMINATION STATISTICS

ARTHUR J. McDOWELL, Director

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

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

JEAN ROBERTS, Chiej Medical Statistics Branch

ROBERT MURPHY, Chiej Survey Pkzrming and Development Branch

COOPERATION OF THE BUREAU OF THE CENSUS

Under the legislation establishing the National Health Survey, the Public

Health Service is authorized to use, insofar as possible, the services or

facilities of other Federal, State, or private agencies.

In accordance with specifications established by the National Center for

Health Statistics, the Bureau of the Census, under a contractual arrangement,

participated in planning the survey and collecting the data.

Vital and Health Statistics-Series 11-No. 152

DHEW Publication No. (HRA) 76-1634

Library of Congress Catalog Card Number 75-619039
CONTENTS

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

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

Blood Specimen and Serum Uric Acid Determination . . . . . . . . . . . . . . . .

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

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

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

Age,Sex,andRace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

PlaceofResidence,Age,andSex . . . . . . . . . . . . . . . . . . . . . . . . . .

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

GeneticandEnvironmentalFactors . . . . . . . . . . . . . . . . . . . . . . . . .

AgeandSexDifferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

PlaceofResidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FamilyIncomeandEducationofParent . . . . . . . . . . . . . . . . . . . . . . .

ClinicalSignificanceofUricAcidLeveIs . . . . . . . . . . . . . . . . . . . . . . .

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

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

Appendix I. TechnicalNotesonMethods . . . . . . . . . . . . . . . . . . . . . . .

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

SonleNotesonResponseRates . . . . . . . . . . . . . . . . . . . . . . . . . . .

PwmlcterimdVarianceEstimates . . . . . . . . . . . . . . . . . . . . . . . . . .

StandmdsofReliabilityandPrecision . . . . . . . . . . . . . . . . . . . . . . . .

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

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

.4ppcndix III. Techniques ofMeasurement and Quality Control . . . . . . . . . . . .

hleasurernent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The HESBlood-Drawing Technique and Its Historical Development . . . . . . .

SerunlUri cAcidDeterminations . . . . . . . . . . . . . . . . . . . . . . . . .

Monitoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

hlethods of Taking Replicate Measurements . . . . . . . . . . . . . . . . . . . .

Results of the Replicate Study for Uric Acid . . . . . . . . . . . . . . . . . . .

Data HandIingV edification. . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

2

2

3

3

3

5

7

8

8

9

9

11

11

12

12

13

15

26

26

27

28

29

29

30

31

31

31

32

32

33

33

35
SYMBOLS

Data not available --------------------------------------- ---

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

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

Quantity more than O but less than 0.05---- 0.0

Figure does not meet standards of

reliability or precision ----------------------------

*
SERUM URIC

OF YOUTHS

ACID VALUES

12-17 YEARS

Paul S. Levy, SC.D., Peter V. V. Hamill, M.D., M.P.H., Felix Heald, M. D., and Michael Rowlanda

INTRODUCTION

This report of serum uric acid 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 (HES).

The means and selected percentiles of the serum

uric acid values are examined here by sex, age,

race, family income, education, and geographic

location in the United States. As described in a

detailed report of its general plan and operational the Health Examination Survey 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 has been described,z and most of the

results are published in other reports in Series 11

of 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 aged 6-11 years. This

aA~~OCiat~professor of Biometry, university of Ilfinois>

School of Public Health; Medical Advisor, Chiidren and Youth

Programs, Division of Hesdth Examination Statistics; Professor of

Pediatrics, Director, Division of Adolescent Medicine, University

of Maryland, School of Me&lcine; Analytical Statistician, Division of Health Examination Statistics, respectively.

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 detailed 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 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 as have the initial

results of the hematocrit findings.g

The present report of uric acid values is the

second in the series presenting findings from the

sample of blood drawn from each youth. No

blood specimens were obtained from the children in Cycle II, but specimens were obtained

from the adults in Cycle L

1
The information from the analysis of blood is

intended for use as much needed reference data

both for clinical and for epidemiologic estimates

of variation in a well-defined population. It also

enables examination of another aspect of growth

and development during adolescence. The procedure by which the Division of Health Examination Statistics obtained advice on the selection

of the analyses to be made on the blood

specimens and the cooperative arrangements

which were subsequently made with the Clinical

Chemistry and Hematology Branch (now Clinical Chemistry Division) of the Center for Disease

Control (CDC) have been described elsewhere.4

The authors and the Division of Health

Examination Statistics are grateful for the technical advice given by Dr. Gerald Cooper and Dr.

Akin Mather and for their administrative assistance in arranging the laboratory determinations

that were performed by the Clinical Chemistry

and Hematology Branch, and to Mrs. Margie

Sailors for coordination and verification of the

laboratory data and its transmission.

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-t ype 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 3%-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 other

stations, so that at the end of 3% 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,~

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

measurements, examination of blood and (on

girls only) urine cultures for bacteria, and a

privately administered health behavior and attitude questionnaire.

Blood Specimen and Serum Uric Acid Determination

The analyses for serum uric acid were performed for the Health Examination Survey by

the Clinical Chemistry and Hematology Branch

of the Center for Disease Control, Public Health

Service, Atlanta, Ga. They employed an automated calorimetric phosphotungstic acid procedure on the Technicon AutoAnalyzer-I using

the N-13b method.’ The assays were controlled

by a manual reference (Brown) method, and the

automated results were originally validated

against a uricase assay. The importance of

specifying the type of laboratory method

employed is emphasized in the discussion section, and the technical details of the method are

presented in both the discussion and appendix

III.

bThe entire examination by the psychologists consisted of

two consecutive time periods (70 minutes). Two psychologists

performed identicaI examinations simultaneously at separate

stations.

cProcedure N-13b, Technicon Laboratory Method File, 1965,

Technicon Instruments Corp., Tarrytown, N.Y.

2
The development of the technique used by

the HIM for obtaining and processing the blood

specimen is also described in appendix III. As

described in the hematocrit report,s the microhematocrit was the only complete laboratory

determination performed on the blood specimen

directly in the examination trailers. The bulk of

each blood specimen, after preliminary laboratory preparation, was properly separated into its

various subsamples and packed into specially

devised styrofoam containers for shipment via

air freight to either the Immunogenetics Laboratory of The Johns Hopkins University, Balti-

‘more, Md., or the CDC in Atlanta, Ga.

Frozen serum for the three blood

chemistries—uric acid, total serum cholesterol,

and protein bound iodine (PBI)—was shipped to

the Clinical Chemistry Section of CDC. Within a

day after arrival at CDC (or at the most within

two days), serum for uric acid was thawed,

determinations were promptly made, and the

aliquots for the other two chemical analyses

were sent to the appropriate laboratory. A

specimen of clotted blood was sent directly to

the Venereal Disease Research Laboratory

(CDC) for analysis.

Race

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

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

white youths constituted 84.74 percent of the

total youths examined; Negro youths, 14.76

‘The same classification scheme as used in the 1960 census

was employed here. As described in the reviously mentioned

$’ report on the operation of HES Cycle 111, tlds information was

obtained at the initial household interview by the U.S. Bureau of

the Census fieldworker. The accuracy of the information was

checked at the subsequent home visit by the highly experienced

representative from HES and again at the examination in the

trailer. A final record check by birth certificate turned up only

seven inconsistencies, and these were mostly pertaining to the

category “other races,” Hence, the possible extent of misclassification of the race variable, as described, is so minimal that it

could have no effect on the data analyzed in this report.

However, when comparing the present HES findings to those of

other variously defined racial groupings in the worId, the degrees

of genetic admixture, as fiist dkcussed by Herskowitzg in 1928

and later by Glass and L&10 by Roberts,l 1Y12 and by Reed,13

should be taken into consideration.

percent; and youths of other races, only 0.50

percent. In Cycle II, white children 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 I. The increased

proportion of Negro subjects in Cycle III was

due to their better response rate–the overall

Ne~o 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 data are analyzed independently of a

classi~lcation by race, however, data for these

youths are included.

RESULTS

Age and Sex

The estimated number and percent distribution of male and female youths 12-17 years of

age in each of 19 uric acid groups are shown in

tables 1 and 2, respectively. The patterns shown

in these distributions are discussed below in

terms of a few summary statistics.

The estimated mean uric acid levels for each

of 12 age-sex classes are shown in table 3 and

figure 1. Among male youths 12-17 years of age,

mean uric acid levels increased with age from a

low of 4.4 mg/100 ml in 12-year-olds to a high

of 5.9 mg/100 ml in 16- and 17-year old males.

Differences in mean uric acid levels between

males in consecutive age groups were greatest at

the youngest ages and decreased consistently

with increase in age, from a difference of 0.6

mg/100 ml in the mean uric acid level of

13-year-olds and that of 12-year-olds to no

difference in the mean level of 16- and 17-yearold males. In female youths, on the other hand,

mean uric acid levels were in the 4.6-4.7 mg/100

ml range, with no significant differences

observed among the six age groups. With the

exception of 12-year-olds, males in each age

group showed higher mean uric acid levels than

their female counterparts.

3
Males

-e-

,~

12 13 14 15 16 17

AGE IN YEARS

Figurel. Mean uric acid Ievals for youths 12-17 years of age,

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

Estimated percentiles of the uric acid distributions are shown by age for male and female

youths in table 3 and figures 2 and 3. For each

age-sex group the median and mean were almost

identical, which indicates symmetry of the

distribution about the mean. The pattern of

increased mean uric acid levels with increased

age shown above for male youths also occurred

at the two extremes of the distribution, namely

the 5th and 95th percentiles (table 3). At the

low end of the distribution, the 5th percentile

for 12-year-old males was 2.7 mg/100 ml, but it

increased to a high of 4.2 mg/100 ml (an

increase of 1.5 mg/100 ml) for 17-year-old

males, with the biggest differences between

consecutive age groups occurring among the

younger adolescents. For females, the 5th percentile varied only slightly among the six age

groups within the range of 2.9-3.2 mg/100 ml,

with no consistent increase or decrease with age.

With the exception of 12-year-olds, the 5th

percentile of the uric acid distribution was

consistently higher for males than for females,

with differences between the sexes being greater

for the older youths. At the upper end of the

distribution, namely the 95th percentile, a

similar pattern occurred for both males and

females. For males, the 95th percentile showed

an increase with age from a low of 6.4 mg/100

ml for 12-year-olds to an approximate average of

2

1

0

I I I I I I

12 13 14 .15 16 17

AGE IN YEARS

Fiswe 2. Selected estimated percentiles of the uric ecid distribution in males, by age and sex: United States, 1966-70.

12 13 14 15 16 17

AGE IN YEARS

Figure 3. Selected astimated percentiles of the uric acid djstrlbution in females, by age: United States, 1966-70.

4
8.0 mg/100 ml for 15- to 17-year-olds (an

increase of about 1.6 mg/100 ml), with the

sharpest differences between consecutive age

groups occurring among the younger age groups.

In contrast, among females the 95th percentile

showed little or no change with age, staying in

the 6.4-6.6 mg/100 ml range over all age groups.

Again, beginning with age 13, the 95th percentile was higher at each age group for males than

for females. In general, the percentiles discussed

above, when plotted against age, were remarkably parallel for both males and females (figures

2 and 3).

Mean uric acid levels for each age-sex group

are plotted against the percentile distribution of

the opposite sex in figures 4 and 5. Males fall

just short of the 50th percentile for females at

age 12. On the average, the levels for males

continue to rise relative to those of females of

similar chronologic age until the mean reaches

the 90th percentile for females at ages 16 and

17. Conversely, mean uric acid levels in females

fall from just above the 50th percentile for

9

8

7

6

6

4

3

2

1

0

~ 90th

---- - ---- Males

----

75th

~.

., 0

,,

. - 50th

— s 25th

I I I I I [

12 13 14 15 16 17

AGE IN YEARS

Figure 4. Mean uric acid levels of males 12-17 years of age,

plotted on the percentile distribution of females: United

States, 1966-70.

9

t

~: : @=:

:@==

50th

CJ

25th

Females

------ ----- ---------- ------ .

g

K

Ioth

34 5th

z

~

z

3

2

I

1.

o~12 13 14 15 16 17

AGE IN YEARS

\

Fiaure 5. Mean uric acid levels of females 12-17 years of age,

plotted on the percentile distribution of males: United

States, 1966-70.

males at age 12 to just above the

for males at ages 16 and 17.

Age, Sex, and Race

Oth percentile

The estimated number of white and Negro

youths in each of 19 uric acid groups is shown in

tables 4 and 5 and equivalently as a percentage

distribution in tables 6 and 7. The patterns

observed in these distributions are discussed

below.

Mean uric acid leveIs are shown by age for

white and Negro males and females (table 8 and

figure 6). In each of the six age groups, white

males had higher mean uric acid levels than

Negro males of the same age group, and white

females had higher mean uric acid levels than

Negro females of the same age group. The

average difference over all age groups in mean

uric acid levels of white youths and those of

Negro youths of the same age group was about

0.6 mg/100 ml in males and about 0.5 mg/100

ml in females. The increase with age in mean

5
01 I 1 I I I I

12 13 14 15 16 17

AGE IN YEARS

Figure 6. Mean uric acid levels of youths 12-17 years of age, by

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

uric acid levels shown above for the total

population of male youths occurred separately

in white males and in Negro males. In white

males, however, the increase with age in mean

uric acid leveled off after age 15, whereas in

Negro males, the increase with age seemed to

continue through age 17. On the other hand, the

lack of increase with age in mean uric acid levels

shown previously for the total population of

female youths was also apparent when white and

Negro females were examined separately.

Selected percentiles of uric acid levels are

shown for white and Negro youths by age and

sex in table 8, and figures 7-10. In general, the

differences between white and Negro youths

discussed above for the mean of the distribution

were also observed at about the same order of

magnitude for the lower end of the distribution

(5th, 10th, and 25th percentiles), for the

median, and for the upper end of the distribution (75th, 90th, and 95th percentiles).

The percentage of white and Negro youths

having uric acid levels above 7.9 mg/100 ml, 8.4

mg/100 ml, and 8.9 mg/100 ml is shown in table

9. For each of the six age groups, the proportion

of males with levels above 7.9 mg/100 ml and

8.4 mg/100 ml was greater among white than

among Negro youths. Likewise, except for

16-year-olds, a higher proportion of white males

9

t

L______ 12 13 14 15 16 17

AGE IN YEARS

Figure 7. Selected estimated ~ercentiles of the uric acid distribution in white males, by age: United States, 1966-70.

:L12 13 14 15 16 17

AGE IN YEARS

Figure 8. Selected estimated percentiles of the uric acid distribution in Negro males, by age: United States, 1966-70.

6
9

8

7

- 95th

90th

● 50th

2

1

I

.

12 13 14 15 16 17

AGE IN YEARS

Figure 9. Selected estimated percentiles of the uric acid distribution in white females, by age: United States, 1966-70.

than of Negro males had uric acid levels above

8.9 mg/100 ml. In the Negro female group, there

were no persons with levels above 7.9 mg/100

ml, whereas for white females, each of the six

age groups had some persons with uric acid

levels above 7.9 mg/100 ml.

Annual Family Income, Education of Parent,

Age, and Sex

Mean uric acid levels are shown by sex, age,

and annual family income in table 10 and figure

11. Few, if any, differences were found in mean

uric acid levels between the subgroups having

low or moderate family income and those having

relatively high family income. Similar results

were found when the data were examined in

terms of sex, age, and education of parent (table

11 and figure 12). Likewise, when the six age

groups were combined for white and Negro

females, uric acid levels of white females were

higher than those of Negro females, regardless of

annual family income or education of parent

(table 12).

o~12 13 14 15 16 17

AGE IN YEARS

— Males, annual family income lessthan $3,000

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

------- Females, annual family income lessthan $3,000

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

Figure 10, Selected estimated percentiles of the uric acid distribution in Negro females, by age: United States, 1966-70.

Figure 11. Mean uric acid levels for youths 12-17 years of age,

by annual family income, age, and sex: United States,

1966-70.

7
6.5, -

g 6.0

z

.>.---. -.-.+ ----------

8

~ 5.5

~

g

: 5.0

g

K . ..>.

; 4.5

~

.

12 13 14 15 16 17

AGE IN YEARS

— Males, edusation of parent leasthan 8 years

------ Malea, education of parant 13 yeara or mora

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

----- Females, edusation of parent 13 yaws or more

Figure 12. Mean uric acid levels for youths 12-17 years of age,

by education of parent, age, and sex: United Statas, 1966-70.

Place of Residence, Age, and Sex

Mean uric acid levels are shown for white

males and females by place of residence (table

13). Mean serum uric acid levels were highest

among those residing in rural farm areas, with

differences being more pronounced for white

males than for white females.

DISCUSSION

In the interpretation of uric acid levels

obtained in any study, the laboratory method

used is extremely important, as summarized by

Wyngaarden.l 4 In general, these procedures can

be classified as either calorimetric or enzymatic

spectrophotometric (uricase). The calorimetric

methods are based on the principle that a blue

color results from the chemical reaction of uric

acid with (usually) phosphotungstic acid, and

that the intensity of this blue color is proportional to the amount of uric acid in the sample.

The enzymatic method, on the other hand, uses

the ultraviolet light-absorbing property of uric

acid. In this procedure, the amount of ultraviolet light absorbed by a particular serum

sample is measured before and after addition of

the enzyme uricase which converts uric acid to

allantoin. The difference in absorption is proportional to the concentration of uric acid in the

sample, and the concentration is measured by

comparison with a calibrated standard.

Since a uricase method is both more specific

and potentially more accurate, it is generally

more accepted as the reference. On the other

hand, it is a more costly and time-consuming

laboratory procedure; therefore investigators

using other methods should demonstrate the

relationship of their method to a uricase

method. The calorimetric method used in determining HES levels performed by CDC was

originally validated against uricase assays and

produced values that averaged about 0.5 mg/100

ml higher. Therefore, when the HES data are

compared with data from Tecumseh, Mich.,1s

which were determined by a uricase method

(table 14), 0.5 mg/100 ml was subtracted from

the HES mean values as the most reasonable

adjustment.

There are many variables that influence uric

acid values in healthy individuals. First of all, as

already discussed, the laboratory technique used

is extremely important in the interpretation of

uric acid determinations.l 6Y17 Likewise, a small

diurnal variation has been reported, with highest

levels occurring in midafternoon.l 8 HES findings, however, showed no differences between

the mean uric acid levels of those youths

examined in the morning and those examined in

the afternoon. Several studies have found a

positive association between uric acid and body

size variables such as weight, relative weight,

surface area of the body, and ponderal index

and somatotype. 16,19,20,22 In ~most every

study in which both male and female subjects of

comparable age have been used, it was found

that postpubertal uric acid levels were higher in

males than in females.1s,2~‘27 Some studies

have shown that mean uric acid levels in males

remain relatively stable during adult life, and

8
that female mean values, after remaining stable

throughout the childbearing years, increase at

the time of menopause.15 ‘z 6~Z8 In a study by

Zalokar et al.20 of over 6,000 healthy

male subjects, the positive relationship between

age and uric acid levels noted above disappeared

when the data were adjusted for percent body

fat, and, in fact, a negative relationship was

found between age and uric acid when the data

were so adjusted. HES findings on the relationship between uric acid levels and such variables

as height, weight, and hematocrit will be discussed in a future report.

Genetic and Environmental Factors

The relative influence of genetic and environmental factors on uric acid levels has been

investigated. A study by Boyle et al.29 of 51

monozygotic twin pairs (16 male, 35 female)

and 61 dizygotic twin pairs (11 male, 20 female,

and 30 of unlike sex) revealed that the intrapair

variance in uric acid levels among female dizygo tic twin pairs was significantly higher than

those among monozygotic female twin pairs. In

contrast, no significant difference was found

between the intrapair variance among male

dizygotic twin pairs and that among male

monozygotic pairs. From this they concluded

that a fairly strong genetic influence on uric acid

level exists in females, but probably not in

males. An additional finding of this twin study

was that in both the monozygotic and dizygotic

female twin pairs, the intrapair variance among

those twins living apart for more than a year was

greater than that found among those living

together in the same household, and from this

they concluded that environmental as well as

genetic factors act as determinants of uric acid

levels.z 9 An earlier study by Jensen et al.30 of a

smaller number of twin pairs also showed

significantly greater intrapair variation in uric

acid levels among the dizygotic than among the

monozygotic pairs, but these results were not

analyzed separately by sex. Like the Boyle et al.

study,z 9 other studies on familial aggregation of

uric acid levels have shown evidence of stronger

genetic determination in females than in

males.3 1,32

While several studies have shown racial differences in uric acid levels, the findings have not

been consistent over different studies. For

example, Ford and DeMos,33 in a survey of 200

healthy Caucasian males, 100 healthy Chinese

males, and 237 healthy Haida Indian males,

showed that the Chinese males had significantly

higher mean uric acid levels than the Caucasians

and Haida Indians. On the other hand, Duff et

al.~ 7 found that although urban Chinese from

Malaya had high mean serum uric acid levels

relative to Caucasians from Tecumseh, Mich.,

Chinese from Taiwan had lower mean uric acid

levels than the Tecumseh Caucasians. A study34

conducted in Alabama indicated that Negro

adult males and females had higher uric acid

levels than Caucasians, a finding which differs

from those of HES for the adolescent age group.

While association between serum uric acid

levels and certain socioeconomic variables has

been found by some investigators but not by

others,z3~z6~3sY36 perhaps the most curious

finding from epidemiologic studies of uric acid is

the association between uric acid levels and such

psychosocial variables as drive, achievement, and

leadership.z1~35 ~37‘39 In a much quoted study,

Dunn and his coworkers 1 found that executives had higher uric acid levels than craftsmen.

Likewise, Kasl and his coworkers,s5)38 in a

study of teenage males, found a strong association between serum urate levels and high school

grade point average, college attendance, and

extracurricular and social activities. At the same

time, no association was found between uric

acid levels and either education of parent or

family income, in accordance with similar HES

findings. On the basis of such evidence, Kasl et

~.s 5,3T,38 present a case for the role of LU5C

acid as a cortical stimulant inducing achievement.

Age and Sex Differences

The increase with age in the mean uric acid

levels of male youths from age 12 to age 15 is a

9
striking finding of this survey. There was a

14-percent increase in mean uric acid levels

between 12- and 13-year-olds, a 10-percent

increase between 13- and 14-year-olds, and a

5-percent increase between 14- and 15-year-olds.

Thus, in a period of 3 years, mean uric acid

levels increased from 4.4 mg/100 ml in 12-yearold males to 5.8 mg/100 ml in 15-year-old males

(an increase of 32 percent).

There were no differences observed among

the older adolescent males, i.e., those aged 15,

16, and 17 years. Some insight into whether

most adolescent males 15-17 years of age have

reached their adult uric acid levels comes from

comparing the levels obtained by HES for males

aged 15-17 years with those obtained for young

adults by other investigators. Findings by

Zalokarz O~AO in a study of Parisian male civil

servants showed mean uric acid levels of 5.8-5.9

mg/100 ml in young adults aged 20-29 on the

basis of calorimetric determinations (the same as

those used for the HES data). The Tecumseh

study, using the uricase enzymatic method,

showed mean levels of 5.39 mg/100 ml in young

males 20-29 years of age.1 5 However, since the

calorimetric method used in HES data produces

values approximately 0.5 mg/100 ml higher than

those produced by uricase assays, adjustment of

the Tecumseh findings for males aged 20-29

years would bring them in line with HES

findings for males aged 15-17 years. Thus, on

the basis of these comparisons, there seems to be

substantial evidence that adult uric acid levels

are reached in most males as early as 15 years of

age. In the Metropolitan Life Insurance Co.

study of 1,077 male and 1,388 female employees, however, males under 35 had substantially higher mean uric acid levels (6.4 mg/100

ml based on calorimetric determinations) than

those obtained by HES for 15- to 17-year-old

males.z 6 The uric acid levels of males in the

Metropolitan Life Insurance study were much

higher than those obtained for males elsewhere

in the literature, with the exception of those

male executives found by Dunn et al.z 1 Because

the males represented in the Metropolitan Life

Insurance data may have included a large proportion of executives, and because executives

were shown to have high uric acid levels in at

least one study,z 1 caution should be exercised

in the interpretation of any comparisons involving these male life insurance employees.

In contrast with males, HES female youths

showed no increase with age in mean uric acid

levels, and only at age 12 were the mean levels

higher than those of HES males (4.6mg/100 ml

in 12-year-old females vs. 4.4 mg/100 ml in

12-year-old males). The mean uric acid levels of

4.6-4.7 mg/100 ml obtained by HES for female

youths aged 12-17 years were only slightly

higher than those of 4.4 mg/100 ml obtained for

females under 35 in the Metropolitan Life

Insurance study.z 6 Females 20-34 years of age

in the Tecumseh studyl s had mean uric acid

levels of 4.0 mg/100 ml by the uricase method;

and if the 0.5 mg/100 ml adjustment were made,

it would bring theirs closely in line with the

levels obtained by HES for adolescent females.

Thus, there is substantial evidence that female

adolescents already have uric acid levels that are

similar to those of young adult females.

The findings of an increase with age in mean

uric acid levels among the HES males but not

among the females somewhat resemble HES

findings of an increase with age in mean hematocrit among males, but not among females.s

Because of the size of the sample on which

they are based and because this is a probability

sample chosen to be representative of U.S.

youths 12-17 years of age, the HES data give the

best picture at the present time of uric acid

levels in adolescent males and females. The only

other population study which gives uric acid

data in enough detail to compare by age and by

sex with the HES findings is the first Tecumseh

study, conducted in 1959-60.15

As was mentioned above, uric acid levels in

the first Tecumseh study were determined by an

enzymatic (uricase) assay, whereas HES determinations were made by a calorimetric method

which when assayed against uricase gave results

that were approximately 0.5 mg/100 ml higher

than those obtained with the enzymatic method.

Table 14 shows for each age group the mean uric

acid levels found in the Tecumseh study alongside the HES uric acid levels, which are reduced

10
by 0.5 mg/100 ml so as to compare more

reasonably with enzymatic determinations of

uric acid levels. At almost every age group, the

two studies produced means that were very close

to each other (sample size for the Tecumseh

study adolescents was much smaller than that

used for HES, which can account for the

fluctuations seen in Tecumseh data when

examined by single years of age). As can be seen

from table 14, age-sex relationships occurred in

Tccumseh data that were similar to those

observed in HIM, namely an increase with age in

male but not in female adolescents.

The Tecumseh study also gives uric acid levels

for children 5-9 years of age, and it was found

that the mean uric acid levels for children in this

age group were approximately the same for boys

as for girls (3.63 mg/100 ml for 5-to 9-year-old

boys; 3.71 mpjl 00 ml for 5- to 9-year-old girls)

imd that these mean serum levels were lower

than those found in 12-year-olds.

The large sex difference in serum urate levels

which first emerges during adolescence has

aroused little interest heretofore. There are no

data in the literature which would suggest that

differing rates of production of uric acid

between boys and girls could account for these

diffmcnces. There are data, however, on the

renal clwmmcc of urates in children who have

hi~hcr rend cleamnces than adults.4 I Among

adults, worncn have higher renal clearances than

men, a fact which would explain at least some of

the scx difference in serum urate levels.42

Differences in body mass (estimated by body

weight, surfiice area, or ponderal index) have

been reported to be important predictors of

hyperuricemia.43 Whether the pubescent differences in body composition are in any way

related to the developing differences in serum

urates remains to be demonstrated. In similar

lhshion, the relationship between the endocrine

events at pubescence and serum urate levels

likewise remains a possibility. This is suggested

by the changes at pubescence documented in

this report and further suggested by the rise in

serum urate levels in women in their late forties

or early fifties concurrent with menopause.

Although this rise in serum urate level at the

time of menopause is well documented, little is

known about the relationship between uric acid

metabolism and the normally functioning

endocrine system.

Race

A remarkably consistent average difference of

approximately 0.5 mg/100 ml between mean

serum uric acid values of white and Negro

youths appeared for both HES males and

females. Since these are the only population

data on uric acid levels in both Negro and white

adolescents comprehensive enough to permit

analysis of racial differences, they cannot be

related directly to the findings of other studies.

As mentioned above, other studies of uric acid

levels in several adult populations have shown

racial differences, however, these differences

have not always been consistent from study to

study. Data from a study on Negro and white

adult males and females in Alabama showed that

Negro males and females had higher uric acid

levels than their white counterparts, a finding

which contrasts with HES data on

adolescents.34

Since uric acid determinations were not performed on adults in HES Cycle I, it cannot be

determined whether the racial differences for

uric acid found in adolescents are also true for

adult Americans. Cycle III data also showed that

Negro adolescents, both male and female, have

lower hematocrits than white youths of

comparable age and sex.s However, racial differences in hematocrit values were primarily at

the lower end of the distributions whereas

differences between uric acid levels of Negro

adolescents and those of white adolescents

appeared throughout the distribution—i.e., the

5th, 50th, and 95th percentiles.

Place of Residence

The fact that white adolescents from farms

had slightly but consistently higher mean uric

acid levels than comparable suburban and city

residents is an interesting finding and one that

cannot be related to other studies. However,

11
the differences found, although consistent, were

small.

Family Income and Education of Parent

Even when standardized for racial differences,

no relationship was found between uric acid

levels of HES youths and education of parent or

family income for either Negro or white persons.

Although Acheson23 found a relationship

between uric acid levels and social class in

England and also in New Haven, the relationship

was weak and was an inverse one, with uric acid

levels decreasing slightly with increase in social

class. HES data confirm earlier findings by Kasl

and his coworkers 8 of a similar lack of relationship between uric acid and education of parent

or family income.

Clinical Significance of Uric Acid Levels

Historically, elevated serum uric acid has been

of interest particularly because of its association

with two extremely painful conditions, gout and

renal stones. These conditions, however, rarely

occur in adolescence, and their clinical importance to these data would lie in what happens to

adolescents with asymptomatic hyperuricemia as

the condition accompanies them to adulthood.

To our knowledge, there have been no longitudinal studies beginning with adolescents that

have dealt tvith the above question. In adults,

the Framingham28 study followed a population

of persons initially aged 30 years and above who

were free of gout; after 12 years, gout was found

to occur in only 1.1 percent of the persons who

initially had uric acid levels under 6.0 mg/100

ml (by the enzymatic method) and in approximately 10 percent of those who initially had

levels above 6.0 mg/100 ml. Thus, development

of gout seems to be a relatively rare occurrence

among persons with asymptomatic hyperuricemia. Other clinical correlates of hyperuricemia are discussed in detail in a recent review

article,l 6 and will be examined in a subsequent

analysis of these HES data.

000

12
REFERENCES

1National Center for Health Statistics: Origin, program, and operation of the U.S. National Health Survey.

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

l-No. 1. Public Health Service. Washington. U.S. GovernmentPrinting Office, Apr. 1965.

2National Center for Health Statistics: Plan and

initial program of the Health Examination Survey. Vital

and Health Statistics. PHS Pub. No. 1000-Series l-No. 4.

Public Health Service. Washington. U.S. Government

Printing Office, July 1965.

3National Center for Health Statistics: Plan, operation, and response results of a program of children’s

examinations. Vital and Health Statistics. PHS Pub. No.

1000-Series 1-No. 5. Public Health Service. Washington.

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

4Nationrd Center for Health Statistics: Plan and

operation of a Health Examination Survey of U.S.

youths 12-17 years of age. Vital and Health Statistics.

PHS Pub, No. 1000-Series l-No. 8. Public Health

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

Sept. 1969.

5National Center for Health Statistics: Height and

weight of youths 12-17 years, United States. Vital and

Health Statistics. Series 1l-No. 124. DHEW Pub. No.

(HSM) 73-1606. Health Services and Mental Health

Administration. Washington. U.S. Government Printing

Office, Jan. 1973.

6National Center for Health Statistics: Body weight,

stature, and sitting height: White and Negro youths

12-17 years, United States. Vital and Health Statistics.

Series 11-No. 126. DHEW Pub. No. (HRA) 74-1608.

Health Resources Administration. Washington. U.S.

Government Printing Office, Aug. 1973.

7National Center for Health Statistics: Skinfold

thickness of youths 12-17 years, United States. Vital and

Health Statistics. Series 11-No. 132. DHEW Pub. No.

(HRA) 74-1614. Health Resources Administration.

Washington. U.S. Government Printing Office, 1974.

8National Center for Health Statistics: Hematocrit

values of youths 12-17 years, United States. Vital and

Health Statktics. Series 1l-No. 146. DHEW Pub. No.

(HRA) 75-1628. Health Resources Administration.

Washington. U.S. Government Printing Office, Dec.

1974.

9Herskowits, M. J.: The American Negro; a Study in

Racial Crossing. New York. Alfred A. Knopf, 1928.

10Glass, B., and Li, C. C.: The dynamics of racial

intermixture-an analysis based on the American Negro.

Amer.J.Hum.Genet. 5(1):1-20, Mar. 1953.

11Roberts, D. F.: The dynamics of racial intermixture in the American Negro: Some anthropological

considerations. Amer. J.Hum. Genet. 7(4):361-367, Dec.

1955.

12Roberts, D. F., and Hioms, R. W.: The dynamics

of racial intermixture. Amer. J. Hum. Gen

14(3):261-277, Sept. 1962.

13Reed, T. E.: Caucasian genes in American Negroes.

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

14Wyngaarden, J. B., and Kelley, W. N.: “Gout,” in

J. B. Stanbury, J. B. Wyngaarden, and D. S. Fredrickson,

eds., The Metabolic Basis of Inherited Disease, 3rd ed.

New York. McGraw-Hill Book Co., 1972. pp. 889-950.

15Mikkelsen, W. M., Dodge, H. J., and Valkenburg?

H.: The distribution of serum uric acid values in a

population unselected as to gout or hyperuricemia.

Tecumseh, Michigan, 1959-1960. Amer.J.Med.

39(2):242-251, Aug. 1965.

16 Fessel, W. J.: Hyperuricemia in health and disease.

Seminars in Arthritis and Rheum. 1:275-299, Spring

1972.

17Bywaters, E. G. L., and Holloway, V. P.: Measurement of serum uric acid in Great Britain in 1963.

Ann. Rheum.Dis. 23(3):236-239, May 1964.

18Rubin, R. T., Rahe, R. H., and Arthur, R. J.:

Serum uric acid, cholesterol, and cortisol levels. Interrelationships in normal men under stress.

Arch. Intern.Med. 125:815-819, May 1970.

1‘Myers, A. R., et al.: The relationship of serum uric

acid to risk factors in coronary heart disease.

Amer.J.Med. 45:520-528, Oct. 1968.

20 Zalokar, J., et al.: Epidemiology of serum uric acid

and gout in Frenchmen. J. Chron. Dis. 27:59-75, Feb.

1974.

21 Dunn, J. P., et al.: Social class gradient of serum

uric acid levels in males. J.A.M.A. 185(6) :431-436, Aug.

10, 1963.

22 Acheson, R. M., and Du V. Florey, C.: Bodyweight, ABO blood-groups, and altitude of domicile as

13
determinants of serum-uric-acid in military recruits in

four countries. Lancet, Vol. 2, Part 1:391, Aug. 23,

1969.

23Acheson, R. M.: Social class gradients and serum

uric acid in males and females. Brit.Med.J. 4:65-67, Oct.

11, 1969.

24 Finn, R., et al.: Frequency distribution curve of

uric acid in the general population. Lancet, Vol. 2, Part

1:185, July 23, 1966.

25 Gephardt, M.C.G., HanIon, T. J., and Matson, C.

F.: Blood uric acid values as related to sex and age.

J.A.M.A. 189(13):1028-9, Sept. 28, 1964.

26 “Biochemical Profiles.” Statistical Bulletin Metropolitan Life. 50:2-9, Dec. 1969.

27 Duff, I. F., et al.: Comparison of uric acid levels in

some oriental and Caucasian groups unselected as to

gout or hyperuricemia. Arthritis Rheum. 11:184-190,

Apr. 1968.

28 Hall, A. P., et al.: Epidemiology of gout and

hyperuricemia. A long-term population study.

Amer.J.Med. 42:27-37, Jan. 1967.

29 Boyle, J. A., et al.: Relative roles of genetic and

environmental factors in the control of serum uric acid

levels in normouricaemic subjects. Ann. Rheum.Dis.

26(3):234-238, May 1967.

30Jensen, J., et al.: Serum lipids and serum uric acid

in human twins. ]. Lipid Res. 6(2):193-205, Apr. 1965.

31 French, J. G., et al. : A study of familial

aggregation of serum uric acid levels in the population of

T e cumseh, Michigan, 1959-1960. Amer.J.Epidem.

86:214-224, July 1967.

320’Brien, W. M., Burch, T. A., and Bunim, J. J.:

Genetics of hyperuricemia in Blackfeet and Pima

Indians. Ann. Rheum.Dzk. 25(2):117-119, Mar. 1966.

33 Ford, D. K., and DeMos, A. M.: Serum uric acid

levels of healthy Caucasian, Chinese and Haida Indian

males in British Columbia. Canad.Med.Ass.J.

90:1295 -1297, June 6, 1964.

34 Casey, A. E., et al.: Race-sex values of serum

creatinine, phosphokinase, uric acid, urea nitrogen and

creatinine. Ala.J.Med. Sci. 5(4) :474-476, Oct. 1968.

35 Kasl, S. V., Brooks, G. W., and Rodgers, W. L.:

Serum uric acid and cholesterol in achievement behavior

and motivation. II. The relationship to college attendance, extracurricular and social activities, and vocational aspirations. J.A.M.A. 213(8):1291-1299, Aug. 24,

1970.

36 Noel, W. K., and Kilmore, M. A.: Socioeconomic

status and blood chemistry. J.Am. Osteopath.Ass.

70:1103 -1107, June 1971.

37 Mueller, E. F., et al.: Psychosocial correlates of

serum urate levels. Psychol. Bull. 73(4):238-257, Apr.

1970.

‘8 Kasl, S. V., Brooks, G. W., and Rodgers, W. L.:

Serum uric acid and cholesterol in achievement behavior

and motivation. I. The relationship to ability, grades,

test performance and motivation. J.A.M.A.

213(7):1158-1164, Aug. 17, 1970.

39 Brooks, G. W., and Mueller, E. F.: Serum urate

concentrations among university professors. Relation to

drive, achievement, and leadership. J.A.M.A.

195(6):415-418, Feb. 7, 1966.

40 Zalokar, J., et at.: Serum uric acid in 23,923 men

and gout in a subsample of 4257 men in France.

J. Chron.Dis. 25(5):305-312, May 1972.

41 Wolfson, W. Q., et al.: Endocrine factors in gout:

The significance of differences in childhood and adult

urate metabolism (abstract). J. Clin.Endocr. 9(7 ):666,

July 1949.

42 Wolfson, W. Q., et al.: The transport and excretion

of uric acid in man. V. A sex difference in urate

metabolism: With a note on clinical and laboratory

findings in gouty women. J. Clin.Endocr. 9(8): 749-767,

Dec. 1949.

43 Acheson, R. M., and Chan, Y. K.: The prediction

of serum uric acid in a general population. J. Chron. Dis.

21:543-553, Jan. 1969.

44 National Center for Health Statistics: Sample

design and estimation procedures for a national health

ex&nination survey of children. Vital and Health Statistics. Series 2-No. 43. DHEW Pub. No. (HRA) 74-1005.

Health Resources Administration. Washington. U.S. Government Printing Office, Aug. 1971.

45 Nation~ Center for Health Statistics: Replication:

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.

14
LIST OF DETAILED TABLES

Table 1. Estimated number of youths aged 12-17 years in the population by uric acid groups, according to sex and age:

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

2. Percent distribution of youths aged 12-17 years by uric acid groups, according to sex and age: United

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

3. Unweighted and weighted sample sizes, mean uflcacid, standard deviation, standard error, and selected percentiles,

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

4. Estimated number ofwhite youths aged 12-17years inthepopulation byuricacid groups, according tosex and age:

5,

6.

7.

8.

9.

10.

11.

12.

13.

14.

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

Estimated numbar of Negro youths aged 12-17 years in the population by uric acid groups, according to sex and

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

Percent distribution of white youths aged 12-17 years by uric acid groups, according to sex and age:

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

Percent distribution of Negro youths aged 12-17 years by uric acid groups, according to sex and age:

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

Unwaighted and weighted sample sizes, mean uric acid, standard deviation, standard error, andselected percentiles,

byrace, sex, andage: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percentage of white and Negro male and female youths aged 12-17 years with uric acid Ievals above 7.9,8.4, and 8.9

mg/lOOml: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Weighted sample size, maan uric acid, and standard error of the mean for youths, byage, sex, and annual family

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

Weighted sample siza, mean uric acid, and standard error of the mean for youths, by age, sex, and education of

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

Weighted sample size, mean uric acid, and standard error of tha mean for Negro and white female youths age~ 12-17

years, byannual family income andeducation ofparent: United States, l966-7O . . . . . . . . . . . . . . .

Mean uric acid, standard error of themean andweighted sample size forwhite youths byplace ofresidence, sex and

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

Mean uric acid levels found in Tecumseh, Mich., alongside HESfindings reduced by 0.5mg/l OOml . . . . . . .

Page

16

17

18

18

19

20

21

22

23

23

24

24

25

25

15
Tablel. Estimated number ofyouths aged 12-17years inthepopulation, byuricacid groups, sex, and age: United States, 1966-70

Uric acid group

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

Under 1.0 mg percent . . . . . .

1.0-1.4 mg percent . . . . . . . .

1.5-1.9 mg percent . . . . . . . .

2.0-2.4 mg percent . . . . . . . .

2.5-2.9 mg percent . . . . . . . .

3. O-3.4 mg percent . . . . . . . .

3.5-3.9 mg percent . . . . . . . .

4,0-4.4 mg percent . . . . . . . .

4,5-4.9 mg percent . . . . . . . .

5.0-5.4 mg percent . . . . . . . .

5.5-5.9 mg percent . . . . . . . .

6.0-6.4 mg percent . . . . . . . .

6.5-6.9 mg percent . . . . . . . .

7s0-7.4 mg percent . . . . . . . .

7.5-7.9 mg percent . . . . . . . .

8.0-6.4 mg percent . . . . . . . .

8.5-8.9 mg percent . . . . . . . .

9.&9.4 mg percent . . . . . . . .

9.5mg 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

Estimated number of youths in population in thousands

?,032

—

6

43

129

248

389

331

319

218

140

132

41

24

10

3

—

—

—

2,006

3

12

42

138

220

289

293

337

244

196

102

62

34

14

10

5

5

1,951

—

—

—

3

24

48

135

193

267

331

310

267

149

97

62

43

14

3

3

I ,900

—

—

—

—

5

28

56

165

215

311

321

227

194

176

101

56

38

—

6

1,836

4

32

15

53

73

154

298

341

363

183

141

74

52

35

8

11

1,764

—

—

4

21

27

152

206

281

307

284

211

124

74

24

14

21

12

,970

—

—

8

29

51

177

272

456

383

259

134

95

73

25

4

4

—

—

—

1,946

—

—

7

30

86

154

280

405

364

287

139

94

50

29

5

6

4

3

6

1,901

—

3

25

42

161

263

406

351

299

163

84

57

35

7

3

—

—

2

1,851

—

6

19

30

172

234

337

406

277

178

101

36

20

11

7

15

—

—

1,789

22

41

143

359

300

338

270

145

68

43

33

14

5

2

4

1,746

2

40

39

152

263

376

290

259

134

107

39

18

11

12

4

16
Table2. Percant distribution ofyouths aged 12-17years byuricacid groups, according tosex and age: United States, 1966-70

Uric acid group

All groups . . . . . .

Under 1.0 mg percent .

1.0-l.4mg parcent . .

1,5-1 .9mg percent . .

2.0-2,4mg percent . .

2.5-2 .9mg percent . .

3,Ck3.4mg percent . .

3.5-3,9 mgparcent . .

4,0-4,4 mg percent . .

4.5-4.9 mg percent . .

5.O-5.4 mg percent . .

5.5.5 .9mg percent . .

6,0-6.4 mg percent ,.

6,5-6.9 mg percent . .

7. O-7.4 mg percent . .

7.5-7,9 mg percent . .

8,0.6 .4mg percent ,.

8.5.8,9 mg percent . .

9.0-9,4mg parcant . .

9.5 mg percant and over

Male

12 13 14 15 16 17

years years years years years years

100.0

.0.3

2.1

6.4

12.2

19.1

16.3

15.7

10.7

6.9

6.5

2.0

1.2

0.5

0.1

100.0

—

—

0.2

0.6

2.1

6.9

11.0

14.4

14.6

16.8

12.2

9.7

5.1

3.1

1.7

0.7

0.5

0.3

0.2

100.0

—

—

0.2

1.2

2.5

6.9

9.9

13.7

17.0

15.9

13.7

7.7

5.0

3.2

2.2

0.7

0.1

0.2

100.0

—

—

0.3

1.5

3.0

8.7

11.3

16.4

16.9

12.0

10.2

9.2

5.3

3.0

2.0

—

0.3

100.0

—

0.2

1.7

0.8

2,9

4.0

8.4

16.2

18.6

19,8

10.0

7.7

4.0

2.9

1.9

0.4

0.6

Female

12 13 14 15 16 17

years years years years years years

Percent distribution

100.0

—

—

—

0.2

1.2

1.6

8.6

11.8

16.0

17.4

16.1

11.9

7.0

4.2

1.4

0.8

1.2

0.7

100.0

—

—

0.4

1.5

2.6

9.0

13.8

23.2

19.5

13.1

6.8

4.8

3.7

1.3

0.2

0.2

—

100.0

—

—

0.3

1.6

4.4

7.9

14.4

20.8

18.7

14.8

7.2

4.8

2.6

1.5

0.3

0.3

0.2

0.1

0.3

100.0

—

—

0.1

1.3

2.2

8.5

13.8

21.4

18.4

15.7

8.6

4.4

3.0

1.8

0.4

0.2

—

0.1

100.0

—

0.3

1.0

1.6

9.3

12.6

18.2

22.0

14.9

9.6

5.5

2.0

1.1

0.6

0.4

0.8

—

—

100.0

—

—

1.2

2.3

8.0

20.1

16.8

18.9

15.1

8.1

3.8

2.4

1.9

0.8

—

0.3

0.1

0.3

100.0

0.1

2.3

2.3

8.7

15.1

21.5

16.6

14.9

7.7

6.2

2.2

1.0

0.6

0.7

0.2

—

NOTE: Parcents maynotadd tolOO.Odue to rounding.

17
Table3. Unweighed and weighted sample sizes, mean uric acid, standard deviation, standard error, and selected percentiles, by sex

andaga: United States, 1966-70

Sex and age

Percentile

N F s~ SF

5 10 25 50 75 90 95

—

Uric acid in mg/100 ml Male

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

13yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

15 years . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . .

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

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

Female

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

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

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

15yeara . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

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

1.12

1.25

1.21

1.24

1.22

1.18

1.04

1.12

1.05

1.06

1.08

1.08

0.05

0.05

0.05

0.07

0.09

0.07

0.05

0.05

0.05

0.04

0.06

0.05

2.7

3.2

3.6

4.0

3.9

4.2

3.0

2.9

3.1

3.2

3.1

3.0

3.0

3.5

4.0

4.4

4.5

4.4

3.6

4.2

4.7

5.0

5.2

5.1

643

626

618

613

2,032

2,006

1,951

1,900

1,836

1,764

1,970

1,946

1,901

1,851

1,789

1,746

4.4

5.0

5.5

5.8

5.9

5.9

4.6

4.6

4.6

4.7

4.6

4.6

—

4.3

5.0

5.5

5.8

5.9

5.8

4.5

4.5

4.6

4.6

4.5

4.5

5.1

5.8

6.2

6.7

6.6

6.6

5.2

5.2

5.3

5.3

5.2

5.2

—

6.0

6.6

7.0

7.6

7.5

7.3

6.0

6.0

6.0

6.0

5.9

6,0

6.4

7.1

7.7

8.0

8.1

7.8

6.5

6.5

6.6

6,5

6.6

6.4

556

469

547

582

3.3

3.2

3.4

3.4

3.4

3.3

—

3.9

3.9

4.0

4.0

3.8

3.9

586

503

536

469

NOTE: n – sample size; /V –estimated number of children inth Ouwnds; X-mean; s~-standard deviation ;s~ -standard

error of the meen.

Table 4. Estimated number of white youths aged 12-17 years in tha population by uric acid groups, sex, and age: United States,

1966-70

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

Uric acid group

Estimated number of youths in population in thousands

All groups . . . . . . . . . . . . 1,747

~

—

—

4

34

78

212

332

274

282

201

133

125

38

22

10

3

—

—

—

1,729 1,686 1,646

—

16

43

115

163

275

292

200

181

171

98

49

38

—

6

1,594 1,528 1,685

=

—

8

18

34

152

191

392

335

238

124

92

67

25

4

4

—

—

—

1,667 1,633

—

—

—

19

24

119

215

345

307

270

153

79

54

35

7

3

—

—

2

I ,594 1,542 1,502

Under l. Omg percent . . . . . .

1.0-1.4 mg percent . . . . . . . .

1.5-1.9 mg percent . . . . . . . .

2.0-2,4 mg percent . . . . . . . .

2.5-2.9 mg percent . . . . . . . .

3.0-3.4 mg percent . . . . . . . .

3.5-3.9 mgpercent . . . . . . . .

4.0-4.4 mg percent . . . . . . . .

4.5-4.9 mg percent . . . . . . . .

5.0-5.4 mg percent . . . . . . . .

5.5-5.9 mg percent . . . . . . . .

6.0-6.4 mg percent . . . . . . . .

6.5-6.9 mg percent . . . . . . . .

7.0-7.4 mg percent . . . . . . . .

7.5-7.9 mg percent . . . . . . . .

8,0-8.4 mg percent . . . . . . . .

8.5-8.9 mg percent . . . . . . . .

9.0-9.4 mg percent . . . . . . . .

9.5mg percent andover . . . . .

—

—

—

12

24

112

191

257

266

284

213

164

83

59

28

14

10

5

5

—

7

32

99

166

239

287

275

235

143

87

60

41

11

3

3

—

4

—

—

17

11

31

57

128

258

298

314

174

134

70

49

35

4

11

—

—

—

—

4

18

14

108

187

255

269

246

184

115

57

24

14

17

12

—

—

7

22

54

116

232

365

327

241

125

77

50

29

5

6

4

3

6

4

14

21

129

184

—

—

15

28

103

282

265

309

251

122

68

40

31

14

5

2

4

—

40

25

119

218

334

243

233

128

89

32

18

8

12

4

290

363

246

188

88

36

18

11

7

15

18
Table 5. Estimated number of Negro youths aged 12-17 years in thepopulation, by uric acid groups, sex, and age: United States,

1966-70

Uric acid group

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

Under 1.0 mg percent . . . . . .

1.0-1.4 mg percent . . . . . . . .

1.5-1.9 mg percent . . . . . . . .

2.0-2.4 mg percent . . . . . . . .

2.5-2.9 mg parcent . . . . . . . . .

3.0-3.4 mg percent . . . . . . . .

3.5-3.9 mg percent . . . . . . . .

4.04.4 mg percent . . . . . . . .

4.5-4.9 mg percent . . . . . . . .

5.0-5.4 mg percent . . . . . . . .

5.5-5.9 mg percent . . . . . . . .

6,0-6.4 mg percent . . . . . . . .

6.5-6.9 mg percent . . . . . . . .

7.0-7.4 mg percent . . . . . . . .

7.5-7.9 mg percent . . . . . . . .

8.0-6.4 mg percent . . . . . . . .

8,6-8.9 mg percent . . . . . . . .

9.0-9.4 mg percent . . . . . . . .

9.5mgparcent andovar . . . .

Male Female

12 13 14 15 16 17 12 13 14 15 16

years years years years years years years years years years years

Estimated number of youths in population in thousands

280

.

—

2

10

51

36

56

57

32

17

7

7

3

2

—

—

—

262

—

—

3

—

19

25

29

26

25

52

26

28

19

3

7

—

—

—

256

—

—

—

3

17

17

37

27

26

41

35

29

6

10

2

3

3

—

—

241

—

—

—

—

5

12

14

49

52

36

26

25

10

5

3

3

—

—

—

231

—

—

—

14

4

22

16

26

37

43

41

9

8

5

3

—

4

—

225

—

—

—

—

—

3

13

43

21

26

35

31

26

10

14

—

—

4

—

272

—

—

—

11

16

25

81

56

48

18

5

3

7

—

—

—

—

275

—

—

—

8

32

37

47

39

37

46

10

17

—

—

—

—

—

—

266

—

—

3

6

18

42

48

61

44

29

8

5

2

—

—

—

—

—

—

235

—

—

3

5

9

39

49

38

40

26

10

13

—

2

—

—

—

—

—

243

—

—

—

7

13

39

74

35

29

19

21

—

3

3

—

—

—

—

—

17

years

237

—

—

2

—

14

33

45

42

44

26

6

15

6

—

2

—

—

—

—

19
Table6. Percent distribution of white youths aged 12-17 years byuricacid groups, according tosexand age: United States, l966-7O

Uricacid group

All groups . . . . . .

Under 1.0 mg percent.

1.0-l.4mg percent . .

1.5-l .9mg percent . .

2. O-2.4 mg percent . .

2.5-2.9 mg parcent . .

3.0-3.4 mg percent . .

3.5-3.9 mg parcent . .

4.04.4 mg percent . .

4.54.9 mg parcent . .

5.0.5.4mg percent . .

5.5-5,9 mg percent . .

6. O-6.4 mgpercent . . .

6.5-6.9 mg percent . .

7. O-7.4 mg parcent . .

7.5-7 .9mg parcent . .

8.0-8.4mg percent . .

8.5-8 .9mg percent . .

9.0-9.4mg percent . .

9.5 mg percent and

over . . . . . . . . . . .

Male I

Female

12 I

13 I14

I

15

I

16

years yeare years years years

100.0

—

0.2

1.9

4.5

12.1

19.0

15.7

16.1

11.5

7,6

7.2

2.2

1.3

0,6

0.2

—

—

100.0

—

—

0.7

1.4

6.5

11.1

14.9

15.5

16.5

12.3

9.5

4.8

3.4

1.6

0.8

0.6

0.3

0.3

100.0

—

—

—

0.4

1.9

5.9

9.8

14.2

17.0

16.3

13.9

8.5

5.1

3.6

2,4

0.7

0.2

0.2

100.0

—

—

—

—

—

1.0

2.6

7.0

9.9

16.7

17.7

12.1

11.0

10.4

6.0

3.0

2.3

—

0.4

100.0

—

0.2

—

—

1.1

0.7

2.0

3.6

8.0

16.2

18.7

19.7

10.9

8.4

4.4

3.1

2.2

0.2

0.7

17

years

12

years

Percent distribution

100.0

—

—

—

—

0.3

1.2

0.9

7.1

12.2

16.7

17.6

16.2

12.1

7.5

3.7

1.6

0.9

1.1

0.8

100.0

—

—

0.5

1.1

2.0

9.0

11.4

23.3

19.9

14.1

7.4

5.5

4.0

1.5

0.2

0.2

—

—

13

yaars I years I years

100.0

—

0.4

1.3

3.3

7.0

13.9

21.9

19.6

14.4

7.5

4.6

3.0

1.7

0.3

0.3

0.2

0.2

0.4

100.0

—

—

1.2

1.5

7.3

13.2

21.1

18.8

16.5

9.4

4.8

3.3

2.1

0.4

0.2

—

—

0.1

100.0

—

—

0.2

0.9

1.3

8.1

11.6

18.2

22.7

15.4

10.6

5.5

2.3

1.1

0.7

0.5

0.9

—

—

100.0

—

1.0

1,8

6.7

18.3

17.2

20.0

16.3

7.9

4.4

2.6

2.0

0.9

0.3

0.2

0.3

100.0

2.7

1.7

7.9

14.5

22.2

16.1

15,5

8,5

5.9

2.1

1.2

0.5

0,8

0.2

NOTE: Percents maynotadd tolOO.Odue to rounding.

20
Table 7. Percent distribution of Negro youths aged 12-17years byuricacid groups, according tosexand age: United States, l966-7O

Uric acid group

All groups . . . . . .

Under 1.0 mg percent.

1.0-1.4 mg percent .,

1.5-1.9 mg percent . .

2.0-2.4 mg percant . .

2,5-2.9 mg percent . .

3.0-3.4 mg percent . .

3.5-3,9 mg percent . .

4,0-4.4 mg percent . .

4.5.4.9 mg percent . .

5,0-5.4 mg percent . .

5,5-5,9 mg percent . .

6.0-6.4 mg percent . . .

6.5-6.9 mg percent . .

7.0-7.4 mg percent . .

7.5-7.9 mg percent . .

8.0-8.4 mg percent . .

8.5-8,9 mg percent . .

9.0-9,4 mg percent . .

9.5 mg percent and

over .,, ...,,,,,

12

years

100.0

—

—

0.7

3.4

18.4

12.9

20.0

20,2

11.4

6.1

2.6

2.6

1.0

0.6

—

—

—

Male Female

13 14 15 16 17 12 13 14 15 16 17

years years years years years years years years years years years

Percent distribution

100.0

—

1.2

—

7.2

9.6

11.1

9,8

9.6

19.9

9.9

10.8

7.1

1.3

2.5

—

—

—

100.0

—

—

—

1.2

6.7

6.4

14.3

10.6

10.2

16.0

13.7

11.4

2.5

3.9

0.9

1.1

1.1

—

—

100.0

—

—

—

—

2.2

5.1

5.6

20.5

21.7

15.0

10.8

10.2

4.3

2.0

1.2

1.3

—

100.0

—

—

—

—

6.2

1.6

9.3

7.0

11.2

15.9

18.5

17.7

4.1

3.4

2.0

1.4

—

1.6

—

100.0

—

—

—

—

—

1.5

5.8

19.2

9.3

11.5

15.3

13.7

11.7

4.2

6.0

—

—

1.6

—

100.0

—

—

—

3.9

6.1

9.2

29.8

21.4

17.8

6.5

1.8

1.1

2.4

—

—

—

—

100.0

—

—

—

3.0

11.7

13.5

17.2

14.3

13.5

16.8

3.8

6.1

—

—

—

—

—

—

—

100.0

—

—

1.0

2.2

6.7

15.8

17.9

23.0

16.5

11.1

2.8

2.1

0.9

—

—

—

—

—

100.0

—

—

1.1

2.2

3.8

16.4

21.0

16.2

17.2

11.3

4.3

5.5

—

0.9

—

—

—

—

—

100.0

—

_,

2.8

5.2

16.1

30.5

14.5

12.1

7.9

8.6

1.1

1.2

—

—

—

—

—

100.0

—

—

0.9

—

6.1

14.0

19.2

17.7

18.4”

11.0

2.6

6.5

2.7

—

1.0

—

—

—

NOTE: Percents maynotadd tolOO.Odue to rounding.

21
Table 8. .Unweighted and weighted sample sizes, mean uric acid, standard deviation, standard error, and selected percentiles, by

race, sex..-and aqe: United States. 1966-70

Race, sex, and age

White male

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

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

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

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

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

17vears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

White female

12years . . . . . . . . . . . ..o . . . . . . . . . . . . . . . . .

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

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

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

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

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

Negro male

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

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

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

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

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

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

Negro female

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

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

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

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

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

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

n

540

542

527

525

496

417

455

490

484

425

441

393

101

80

88

84

57

69

88

91

101

73

93

74

1,747

1,729

1,686

1,646

1,594

1,528

1,685

1,667

1,633

1,594

1,542

1,502

280

262

256

241

231

225

272

275

235

243

237

4.5

5.1

5.6

6.0

6.0

5.9

4.6

4.6

4.7

4.7

4.7

4.6

3.9

4.9

4.9

5.0

5.3

5.6

4.1

4.2

4.1

4.2

4.1

4.3

—

1.11

1.24

1.16

1.21

1.19

1.16

1.04

1.12

1.05

1.06

1.08

1.08

1.02

1.32

1.32

1.08

1.28

1.27

0.89

1.05

0.92

0.99

0.93

1.03

Uricacidinmg/100 ml

0.05

0.05

0.05

0.07

0.08

0.08

0.06

0.06

0.06

0.05

0.06

0.06

0.09

0.11

0.19

0.12

0.24

0.22

0.11

0.10

0.12

0.13

0.12

0.17

2.9

3.2

3.8

4.1

4.2

4.2

3.0

3.0

3.2

3.2

3.2

3.0

2.6

2.8

2.8

3.4

2.9

3.8

2.6

2.6

2.6

2.9

2.8

2.9

3.2

3.6

4.1

4.5

4.6

4.5

3.4

3.3

3.5

3.5

3.5

3.4

2.7

3.2

3.3

3.8

3.7

4.1

3.1

2.8

2.9

3.2

3.1

3.2

3.7

4.2

4.8

5.1

5.3

5.1

4.0

4.0

4.0

4.1

3.9

3.9

3.1

3.9

3.8

4.3

4.5

4.4

3.6

3.4

3.5

3.6

3.5

3.6

.

4.4

5.0

5.5

5.9

6.0

5.8

4.6

4.6

4.6

4.7

4.6

4.5

3.8

5.0

5.1

4.7

5.5

5.6

4.0

4.1

4.2

4.1

4.0

4.2

5.2

5.8

6.3

6.9

6.6

6.6

5.2

5.3

5.4

5.4

5.3

5.2

4.5

5.7

5.8

5.7

6.1

6.5

4.6

5.0

4.7

5.0

4.7

4.9

6.1

6.6

7.1

7.6

7.6

7.3

6.1

6.0

6.1

6.1

6.0

6.0

5.2

6.8

6.4

6.4

6.9

7.1

5.1

5.5

5.3

5.6

5.5

6.1

—

6.4

7,2

7.8

8.1

8.2

7.9

6.6

6.6

6.7

6.6

6.6

6.5

5.9

7.0

7.0

7.0

7.6

7.6

5.6

6.1

5.8

6.1

5.8

6.2

.

NOTE: n – sample size; N –estimated number of children inthousands; ~-mean ;s~-standard deviation; sx – standard

error of the mean.

22
Table 9. Percentage ofwhite and Negro youths aged 12-17years with uricacid levels above 7.9,8 .4, and8.9m~/l OOml: United States,

1966-70

Sex and uric acid levels

Male

Above 7.9 mgll 00 ml . . . . . . . . . . . . . . . . . . . . . . . .

Above 8,4 mg/100 ml . . . . . . . . . . . . . . . . . . . . . . . .

Above 8.9 mg/100 ml . . . . . . . . . . . . . . . . . . . . . . . .

Female

Above 7.9 mg/100 ml . . . . . . . . . . . . . . . . . . . . . . . .

Above 8.4 mg/100 ml . . . . . . . . . . . . . . . . . . . . . . . .

Above8.9mg/100ml . . . . . . . . . . . . . . . . . . . . . . . .

Age in years

Percent white Percent Negro

2.2

1.1

—

—

—

1.3

—

—

—

—

3.0

1.6

1.6

—

—

0.2

—

0.2

—

—

2.0

1.2

0.6

1.1

0.8

0.6

3.5

1.1

0.4

0.3

0.1

0.1

5.7

2.7

0.4

1.4

0.9

—

6.2

3.1

0.9

0.8

0.8

0.5

4.4

2.8

1.9

1.0

0.2

1.6

1.6

1.6

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Table IO. Weightedsa esize, mean uric acid, and standard error of the mean for youths, by age, sex, and annual family income: United States, 1966-70

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

N X- s~ N J? q N j? *X N j? SF N z q N y ~~

Sex and annual

famllylncome

—Male

All Incomes . . . . . . .

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

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

$5,0Q0.$9,999 . . . . . . . .

$l0,0000rmOre . . . . . .

Don’tkrmw . . . . . . . . . .

Blank or refused . . . . . .

Female

All Incomes . . . . . . .

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

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

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

$l0,000mmOre . . . . . .

Don’t know . . . . . . . . . .

Blank or refused . . . . . .

Uric acid in mgll 00 ml

2.032 4.4

.

4.0

4.4

4.4

4.4

4.5

3.9

4.6

.

4.6

4.5

4.6

4.5

4.4

4.5

—

0.05 2,006 5.0 0.05 5.5

=

5.4

5.5

5.4

5.5

5.7

6.0

I

d

1

4.4

4.5

4.6

4.8

4.5

4.5

—

0.05

0.16

0.17

0.09

0.08

0.34

0.22

0.05

0.21

0.10

0.09

0.09

0.23

0.31

1,90C 5.8

=

5.5

6.0

5.9

5.9

6.1

6.3

4.7

.

4.5

4.5

4.7

4.9

4.5

4.9

—

0.07 1,836 5.9 0.09

0.18

0.14

0.13

0.13

0.26

0.23

0.06

5.8

=

5.8

6.0

5.8

6.0

5.3

5.4

4.6

0.07

0.11

0.14

0.08

0.12

0.52

0.25

0.05

=

0.18

0.17

0.09

0.08

0.15

0.55

1,951 1,764

226

245

692

479

49

74

1,746

—

182

206

586

628

92

52

180 0.17

0.12

0.03

0.07

0.26

0.28

0.05

=

0.15

0.20

0.08

0.10

0.23

1.12

212

264

767

619

65

80

1,946

268

301

802

494

46

35

4.8

5.0

5.1

5.1

5.6

4.6

4.6

0.22

0.17

0.09

0.11

0.28

0.27

0.05

20+3

240

746

597

100

67

,901

241

219

719

598

76

46

1,651

0.16

0.17

0.11

0.10

0.27

0.34

0.04

201

265

719

516

82

55

,769

6.1

5.9

5.B

5.9

5.9

6.3

4.6

308

869

575

55

46

1.970

-.

257

274

722

600

79

37

4.3

4.7

4.6

4.6

4.5

4.6

.

0,17

0.14

0.09

0.09

0.25

0.37

213

300

720

554

72

42

258

264

700

533

63

32

0.17

0.12

0.07

0.08

0.17

0.61

246

166

650

594

83

50

4.6

4.2

4.6

4.6

4.8

5.1

0.13

0.13

0.09

0.09

0.14

0.33

4.4

4.5

4.6

4.6

4.6

4.8

NOTE: N-estimated number ofchildren inthousands; ~-mean; s~-standard error of the mean.

23
Tablell. Weighted sample size, mean uric acid, andstandard error of themean foryouths, byage, sex, and education of parent: United Statas,1966.70

Sax and education

of parent

Uric acid in mg/100 ml

1,951 ] 5.5 I 0.05] 1,9001 5.8

m

172 5.7 0.22 196 5.7

474 5.3 0.13 487 5.8

730 6.4 0.08 727 5.8

549 5.6 0.09 472 6.0

25 4.9 0.87 18 6.3

1,901 4.6 0.05 1,851 4.7 m

me

All education groups .

Less than 8 years . . . . . .

8-11 years . . . . . . . . . . .

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

13 years or more . . . . . .

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

FAll education groups .

Less than 8 years . . . . . .

8-11 years . . . . . . . . . . .

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

13 years or more . . . . . .

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

4.4 I 0.05 I 2,006

lT

4.2 0.25 175

4.2 0.07 502

4.5 0.09 780

4.5 0.09 527

● * 23

2,032 5.01 0.05 1,836 5.9

.

5.9

5.9

5.9

6.0

6.0

4.6

.

4,5

4.4

4,8

4.7

4.5

—

0.07 0.08 1,764 5.8 0.07

5.1 0.23

5.1 0.10

5.0 0.08

5.0 0.10

0.17

0.11

0.10

0.12

0.54

0.04

=

0.20

0.09

0.08

0.05

●

217

474

630

480

35

1,789

187

453

623

512

34

0.30

0.14

0.09

0.14

0.33

0.06

0.18

0.09

0.08

0.11

0.37

208

446

688

388

54

1,746

146

465

525

542

67

5.6

5.8

5.9

6.0

5.9

4.6

0.32

0.10

0.10

0.09

0.85

0.05

-

0.22

0.07

0.11

0.09

0.34

176

543

736

562

16 6.3 0.33

& 4.6 0.05 m

4.7 0.16 228

4.5 0.07 507

4.6 0.10 727

4.5 0.09 463

4.2 0.26 22

1,970

4.5

4.7

4.6

4,5

4.5

211

480

729

509

41

4.6 0.19

4,4 0.10

4.8 0.07

4,5 0.11

● ●

NOTE: N - estimated number of childran in thoussndsj %- mean; ST - standard error of the mean.

Table 12. Weighted sample size, mean uric acid, and standard error of the mean for Negro and white female youths aged 12-17 years,

by annual family income and education of parent: United States, 1966-70

Variable

Negro female I

White female

Annual Uric acid in mg/100 ml family income

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

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

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

$10,000 and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Education of parent

Less than 8 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . .

8-11 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

13 years or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

495

400

407

117

4.2

4.1

4.2

4.0

4.1

4.1

4.3

4.3

0.09

0.07

0.10

0.21

0.10

0.12

0.09

0.15

928

1102

3760

3258

784

2337

3600

2752

4.6

4.7

4.7

4.7

4.7

4.6

4.7

4.6

0.11

0.10

0.05

0.05

0.14

0.04

0.06

0.05

302

679

363

127

- ..

NOTE: N-etiimated numbarof children inthouwnds; ~-mean; s~-standard error of the mean.

24
Table 13. Mean uric acid, standard error of themaan, andweighted sample size forwhite youths, byplace ofresidence, sex, anda~:

United States, 1966-70

Sex and age

we

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

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

14yeers . mm,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years m. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 yaars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Female

12years o. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13yeers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

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

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

17years .. m. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Place of residence

Uricacidinmg/100 ml

4.4

5.2

5.6

6.0

6.0

6.0

4.7

4.7

4.6

4.8

4.6

4.7

—

0.11

0.11

0.12

0.18

0.16

0.22

0.09

0.13

0.14

0.14

0.14

0.13

363

400

369

376

338

372

356

407

339

335

360

392

4.4

5.1

5.5

6.0

6.0

5.9

4.6

4.7

4.8

4.9

4.7

4.5

0.11

0.10

0.08

0.14

0.12

0.12

0.11

0.11

0.12

0.10

0.07

0.11

700

615

594

579

550

441

649

522

572

580

591

531

4.8

5.3

5.8

6.1

6.3

6.2

5.0

4.6

5.0

4.5

4.7

4.7

0.22

0.17

0.27

0.21

0.26

0.14

0.36

0.15

0.35

0.11

0.20

0.18

‘Standard Metropolitan Statistical Area.

NOTE: ~-mean;s~ - standard error of the mean; N —estimated number of youths in thousends.

Table 14. Mean uric acid levels found in Tecumsah, Mich., compared with HES findings reduced by 0.5 mg/100 ml

110

123

125

137

153

119

127

132

119

134

67

121

Male Female

Agegroup

Tecumseh HES adjusted Tecumseh HES adjusted

mean mean mean maan

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

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

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

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

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

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

4.2

4.6

5.0

5.5

5.5

5.7

3.9

4.5

5.0

5.3

5.4

5.4

4.2

4.3

4.5

4.1

4.4

4.1

4.1

4.1

4.1

4.2

4.1

4.1

NOTE: The first Tecumseh study, conducted in 1959.60, yielded thaonlydete on uric acid level datailed anoughtocompereega

fOr age end for sex with HES findings. Because the Tecumsah data were determined by anzymatic (uricasa) assay, and those of H ES by

ecolorimetric method, mathematical adjustment wes necessary soastoenable comparison.

25
APPENDIX 1

TECHNICAL NOTES ON METHODS

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 land-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 H 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

initial 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 households);

household; all eligible youths; and finally, the

sample youth. Every eligible youth within the

defined population has a known and approximately equal 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

strataso that each stratum had an average size of

about 4.5 million persons. This grouping maximized the degree of homogeneity of the PSU’S

within each strata with regard to the population

size, degree of urbanization, geographic proximity to one another, and degree of industrialization. The 40 strata were then classified into four

broad geographic 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 the PSU’S was carried

out in several steps. The first step was the

selection of census enumeration districts

(ED’s)–small, well-defined areas of about 250

housing units. The entire nation was divided into

ED’s for the 1960 population census, and 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 aged 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.

26
Minor changes required in the Cycle III design

were ( 1) that it be supplemented for new

construction to a greater extent than had been

necessary in Cycle H and (2) that reserve

segments be added. Although it was the plan for

Cycle 111 to use the Cycle II segments, it was

recognized that within several PSU’S additional

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 Cycle II had yields of less

than 165 eligible children and several others

were marginal in their yield. In addition, there

was a 3-year interval between Cycle II and Cycle

111, so that it was quite possible for some

segments to have been completely demolished

due to highway construction or urban

redevelopment.

The time available for examinations at a

particular location, or stand, 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 available, excluding Saturdays,

is 17. At the rate of 12 examinations each day,

this provides for 204 examination slots. Examinations are conducted on Saturdays if necessary. Because of rescheduling for cancellations

or no-shows, the maximum number of youths

that is considered for inclusion in the sample is

200. When the number of eIigible youths

exceeds the maximum, 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

dinal study portion 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 sampIe

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 y of being drawn into

the sample.

The adjustment upward for nopresponse 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 III 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 agree 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 (approximate midsurvey point) by color

and sex for each single year of age 12 through

17. The sampling weight of every youth

examined 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

43,4 and in Series l-Numbers 11, 53, and 84,

which describe the plan and operation of the

first three cycles of the Health Examination

Survey.

Some Notes on Response Rates

the Cycle 111 sample but who were examined in

Cycle II and any twin who may have been As mentioned previously, the sample designs

deleted are scheduled, if time permits, for an

of the second and third cycles of the HES were

examination to be included only in the longitu- Note. –A list of references follows the text.

27
similar. Differences did

response rates of various

occur, however, in

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—i.e., the number of youths selected who

were actually examined-decreased from 96 percent in Cycle II to 90 percent in Cycle III. Of

the youths examined in 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

rather, a smaller decrease in response rate for

Negro youths between the two cycles than was

the case for white youths. In actuality, 13.8

percent of the sample selected for examination

was Negro in Cycle III, corresponding to 13.5

percent in 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

far less, from 98.4 percent to 96.6 percent.

Thus, relatively better response from the Negro

portion of the sample in Cycle III increased their

percentage of actual examinations as compared

with the previous cycle.

Examination of sample sizes in this report

clearly shows that at every age group, fewer

females than males were actually examined.

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

done by age, race, and sex, as follows:

can be

Age

White Negro White Negro

male male female timale

Total . . . . . . . . . 90.5 97.6 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 97.8 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 III 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

ex~ined in order ;O 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

pop ulation parameters presented in HES

publications are computed taking this weight

into consideration. Thus, ~, the estimate of a

population mean u is computed as follows:

where Xi is the observation or measurement

taken on the ith person and Wiis the statistical

weight assigned to that person.

The HES has an extremely complex sampling

plan, and obviously, by the very nature of the

sample, the estimation procedure is complex as

well. For estimating the reliability of findings, a

method is required that “reflects both the losses

28
from clustering sample cases at two stages and

the gains from stratification, ratio estimation,

and poststratification. ”*s

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 containing

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.

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, that

statistic is computed for each of the 20 half

samples. Using the mean, xi, as an example, the

w~ighted mean of the entire undivided sample

(X) is computed. The variance of the mean is the

mean square deviation of each of the 20

half-sample means about the overall mean.

Symbolically,

20

~ (jfi – X)2

Var(X) =‘= 1 Z.

and the standard error of the mean is the square

root of Var(~). In a similar manner the standard

error of any statistic may be computed.

A detailed description

process has been published

of this replication

in Vital and Health

&atistics, Series 2--Number 14.45

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 consecutive criteria: that

a sample size be at least five; and that the

estimated coefficient of variation (i.e., the standard error of the mean divided by the mean, or

(S~/~) be less than 25 percent. Thus, if the

sample size was too small, or if, given adequate

sample size, the variation with respect to the

mean was too large, then the estimate was

considered neither precise nor reliable enough to

meet the standards established for publication.

Imputation

In addition to the subject nonresponse discussed above, the problem of item nonresponse

merits consideration here. In this situation,

information about a respondent is complete

with the exception of a missing uric acid value.

Missing data were replaced by the value

recorded for a randomly selected respondent of

similar age, sex, and race. However, when only

one of the two uric acid values was missing, the

recorded measurement was substituted for the

unknown value. This occurred in 38 cases (0.6

percent of total respondents). Imputation where

there was no value recorded for examinees was

necessary in 199 cases (2.9 percent of total

respondents).

In effect, sample cases were sorted into

categories, and within each category the cases

were expected to have high intraclass‘correlation

(i.e., to be 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 of the respondent cases.

.29
APPENDIX II

DEMOGRAPHIC VARIABLES

Regional and demographic characteristics by

which the population has been classified for this

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 verified the age of 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. –Serum uric acid value was reported by

race for white and Negro youths. Youths of

other races were not sampled sufficiently for

comparison purposes and represented only 0.55

percent of the sample.

Re#”on. –Regional data are presented for four

regions of the continental United States.

Re@”on

Northeast . . .

Midwest . . .

South . . . .

States Included

Maine, Vermont, New Hampshire, Massachusetts, Rhode

Island, Connecticut, New

York, Pennsylvania, New Jersey

Minnesota, Wisconsin, Michigan, Iowa, Missouri, Illinois,

Indiana, Ohio

Delaware, Maryland, Virginia,

District of Columbia, West

Virginia, 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 gToss 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 parent 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: graded or private schools, either day

or night schools, with either full-time or parttime 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.

o 0 0

30
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 blood specimens from 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. It

was assumed, therefore, that some had never

been to a physician before and that others

would have very bad memories of and associations with such visits. In addition, because the

sample covered the entire spectrum of behavioral and physical development extant in the

United States, severe technical and behavioral

problems resulting from immaturity of 6- and

7-year-olds would be likely. It was believed that

fear or extreme distaste for having a blood

sample drawn on the part of many potential

subjects might severely affect 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 this line of reasoning.

Now, of course, it can never be known how

great a diminution of the response rate would

have been caused by the inclusion of a blood

sample from younger children in Cycle II.

In the early planning stages of Cycle III, it

was decided to obtain a blood specimen from

the youths 12-17 years if at all feasible, that is,

primarily if the price in terms of diminished

response rate and cooperation of the examinees

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. What was desired

was to draw the optimum amount of blood,

without causing emotional upset to the

examinee, or without affecting his performance

in any of the procedures to follow. 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 greatly

influenced the acceptance or rejection of 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

unfi-ozen blood, 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

spoilage.

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

“timediate HES technical staff, were Dr. Wilma

Bias and Dr. Bernice Cohen of The Johns

Hopkins University; Dr. Gerald Cooper, Chief of

Laboratories, Communicable Disease Center,

Public Health Service, Atlanta, Ga.; the many

teenage subjects during our pretest who gave

valuable suggestions and who pointed out, either

31
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, N.J.

The latter, through several personal visits by a

representative of their technical division, not

only gave excellent technical advice on bloodcollection 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

blood-drawing procedure, including their own

blood in tubes. Therefore, a technique was

employed that minimized the subject’s attention

to the operation. Effective screening was

achieved by having the subject lie down and by

draping and keeping the arm and tubes well

below the level of the examination table. After

the skin area was cleansed with alcohol, the

blood was 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 was inserted into

the holder.

From the one free-flowing venipuncture, a

total of only 55 cms of blood was collected in

four separate vacutainer tubes from all male and

almost half of the female subjects. (The difference was 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 cms drawn.)

Each test tube was 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 use by 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.

Serum Uric Acid Determinations

As already described elsewhere in the report,

the frozen serum was sent via air freight in

styrofoam containers to the Clinical Chemistry

Division, CDC, Atlanta, Ga., for the laboratory

determinations. The serum uric acid levels were

determined by a calorimetric phosphotungstic

acid procedure on the Technicon AutoAnalyzer-I using the N-13b method.’ A description of the general principles of the method and

a listing of the equipment used are quoted

below. The detailed preparation of the reagents

used (which are so crucial to the exact values

obtained), a flow diagram of the AutoAnalyzer1, and the step-by-step procedures are also

documented in the report.’

——

Principle: Semm is passed through a dialyzer where uric

acid and other dkdyzabk solutes are separated from protein.

The protein-free dialysate is mixed with urea and sodium

cyanide reagent, which provides alkalinity, followed by

phosphotungstic acid. The phosphotungstic acid is reduced by

the uric acid under these conditions to produce a blue-colored

substance. The blue color is measured photometrically and

read at 660 m/J .e

Equipment: The uric acid AutoAnalyzer-I is comprised of

the following modules: sampler with 2:1, 40 per hour cam,

pump, dmlyzer, calorimeter, and recorder. All waste was

ddned directly into a sink trap and continually flushed with

mrming water so that at no point would it come in contact

with acid with which it could combine to form the very

poisonous HCN.e

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

‘Rocedure N-13b, Technicon Laboratory Method File, 1965,

Technicon Instruments Corp., Tamytown, N.Y.

32
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

tiiking 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 which

includes the objective of overall 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

uncertainty is difficult to evaluate, and most

tittempts are restricted to subjective statements

concerning the direction and/or size of the bias

and the need for concern in the analysis of data.

In this study two extra blood samples were

drawn from a subsample of Cycle III examinees

imd were included in the shipment sent for

processing to the Lipid Standardization Laboratory (now called the Clinical Chemistry and

Hematolobv Laboratory) at the Communicable

Disease Center in Atlanta, Ga. Replicate blood

samples were taken from the same venipuncture

as the regular blood samples and, from shipment

to final processing at the Communicable Disease

Center, were treated the same as the regular

stimplcs. These replicates were labeled with

dummy examination identification numbers and

were recorded by the nurse in a replicate log

book. All samples were submitted for laboratory

analysis with no indication that any two samples

came from the same exarninee. Each sample was

split by the technician and duplicate determinations were performed; if a difference greater

than 0.4 mg/100 ml was found (it was usually a

reading or recording error), a third determination was performed and the two closest determinations were used. The analyses of replicates and

originals were performed under identical laboratory conditions by the same technician in a true

double-blind manner.

Cycle III examinees were chosen systematically for replicate blood determinations. On

every third day of the first 15 days of each

Examination Center, two extra blood samples

were drawn (preferably from girls) for the

replicate study. Since in a voluntary survey it is

impossible to follow a statistically random pro-”

cess in scheduling subjects, the replicate design

did not ensure that its subjects would be

“representative” of those in the larger Cycle III

Health Examination Survey. It is felt, however,

that this is not a crucial issue since the matter of

concern in undertaking the replicate study is not

the determination of possible differences in the

values of the measurements, but rather the

determination of possible differences in errors

associated with the measurements.

Results of the Replicate Study for Uric Acid

Two readings were made of the original split

sample obtained for each of the 6,531 (96

percent of the total sample) examinees by the

same technician. An extra blood sample was

drawn for replicate studies on 424 examinees of

which 96 percent were adequate.

Frequency and percent distributions of the

absolute differences between the duplicated determinations on the original uric acid specimen

and also between the duplicated determinations

on the replicate and original uric acid specimens

are presented in table I. The first two columns

represent the differences between the duplicated

determinations on the original specimen; the

second two columns represent the differences

between the first recorded determination values

of the original specimen and that of the replicate

specimen; and the third two columns represent

33
Table 1. Frequency and percent distribution of absolute differences between duplicated determinations of original

specimens and between original and replicated specimens

Absolute difference (mg/100 ml)

Total . . . . . . . . . . . . . . . . . . . . . . .

0.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Difference between

duplicated

determinations of

original specimen

Frequency

6,531

3,225

2,579

569

114

25

6

5

1

1

1

—

1

1

—

—

1

—

—

1

1

differences between the second (or duplicated)

recorded values of the original and replicate

specimens.

As a summary statistic of the distribution of

differences between replicate and original uric

acid determinations shown in table 1,, we have

computed 1’, the percentage technical error of

measurement which is givenby

Percent

of total

100.0

49.4

39.5

8.7

1.7

0.4

0.1

0.1

—

—

—

—

—

—

—

—

—

—

Difference between original and replicated

specimens

First determinations

Frequency

403

176

147

35

19

7

3

1

1

1

—

2

—

1

—

1

1

3

2

1

1

—

1

—

Percent

of total

100.0

43.7

36.5

8.7

4.7

1.7

0.7

0.2

0.2

0.2

—

0.5

—

0.2

—

0.2

0.2

—

0.7

0.5

—

0.2

0.2

—

0.2

—

Second

determinations

Frequency

402

162

138

61

13

8

3

1

3

1

2

1

2

2

1

1

2

1

Percent

of tota I

100.0

40,3

34.3

15.2

3.2

2.0

0.7

0.2

0.7

0.2

0.5

0.2

0.5

0.5

0.2

0.2

0.5

—

0,2

where

n is the number ofpairs of measurements m

the study,

34
d? is the square of the difference between

&embers of the ith pair of measurements (i =

1$. ..9 n), and

.~ is the arithmetic mean of the Zn measure

ments 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. As one measure

of the differences between specified determinations the values of V are given below.

Specified Determinations v

First determinations on original and replicate specimens 5.2 percent

Second determinations on

original and replicate specimens 5.1 percent

Duplicated determinations

on original specimen 1.8 percent

These values of V, however, mask the essential y excellent reproducibility y that technicians

at the Communicable Disease Center achieved.

When the frequency and percent distributions in

table I are examined, more than 95 percent of

each of the three distributions in the table are

found to be below 0.5 mg/100 ml. The few

extreme outliers account for the differences in V

noted above.

Data Handling Verification

Quality control considerations were not confined to the laboratory. Data were subject to the

possibility of error every time a human hand

touched a keyboard or moved a pencil across a

page. After the data had been put on punchcards, they were transferred to magnetic tape.

Subsequent handling of the data by programmers and transcription by clerks provided other

sources of error.

To verify all operations, the entire cohort of

16-year-old Negro males was subjected to a

thorough independent manual audit. The computer tape printout of each subject’s serum uric

acid value was listed opposite his identification.

These were individually checked against the

values originally recorded at the Communicable

Disease Center. The mean was then computed

manually on the desk calculator and proved

identical to the computer’s mean value.

In addition, ti age, race, and sex identification for members of this cohort were found to

correspond exactly to the information given on

the household interview forms completed by

census interviewers.

000

* U. S. GOVERNMENT PRINTING OFFICE :19’75 21O-9UA

35
VITAL AND HEALTH STATISTICS PUBLICATION SERIES

Formerly Public Health Sewice Publication No. 1000

Srrzks 1. Programs and collection procedures. — Reports which describe the general programs of the National

Center for Health Statistics and its offices and divisions, data collection methods used, definitions,

and other material necessary for understanding the data.

Sevies 2. Data ewzluation and methods research. —Studies of new statistical methodology including: experimental tests of new survey methods, studies of vital statistics collection methods, new analytical

techniques, objective evaluations of reliability of collected data, contributions to statistical theory.

Swim 3, Analytical studies .—Reports presenting analytical or interpretive studies based on vital and health

statistics, carrying the analysis further than the expository types of reports in the other series.

Series 4. Documents and committee repoYts.— Final reports of major committees concerned with vital and

health statistics, and documents such as recommended model vital registration laws and revised

birth and death certificates.

Series 10. Data jrom the Health Intevview Swvev.— Statistics on illness, accidental injuries, disability, use

of hospital, medical, dental, and other services, and other health-related topics, based on data

collected in a continuing national household interview survey.

SL?YicwIl. Data from the Health Examination Sumey. —Data from direct examination, testing, and measurement of national samples of the civilian, noninstitutional population provide the basis for two types

of reports: (1) estimates of the medically defined prevalence of specific diseases in the United

States and the distributions of the population with respect to physical, physiological, and psychological characteristics; and (2) analysis of relationships among the various measurements without

reference to an explicit finite universe of persons.

Wi(?s 12. Datu J1’om the Institutional Population Surveys. —Statistics relating to the health characteristics of

persons in institutions, and their medical, nursing, and personal care received, based on national

samples of es~ablishments providing these services and samples of the residents or patients.

$Wrics 13. Data from the Hospital Discharge Survey. —Statistics relating tc] discharged patients in short-stay

hospitals, based on a sample of patient records in a national sample of hospitals.

;(irics 1,$, Data on )lealtjl Yesources: manpower and facilities. —Statistics on the numbers, geoWaPMc ~smibution, and characteristics of health resources including physicians, dentists, nurses, other health

occupations, hospitals, nursing homes, and outpatient facilities.

%?vic’s 20. Data on movkzlity.-Various statistics on mortality other than as included in regular annual or

monthly reports-b ‘pecial analyses by cause of death, age, and other demographic variables, also

geographic and time series analyses.

;cw’es 21. Datu on rtatulity, mawiage, and divorce. —Various statistics on natality, marriage, and divorce

other than as included in regular annual or monthly reports +pecial analyses by demographic

variables, also geographic and time series analyses, studies of fertility.

Writs 22. Data from the National Natality and h~ortality Surveys. — Statistics on characteristics of births

and deaths not available from the vital records, based on sample surveys stemming from these

records, including such topics as mortality by socioeconomic class, hospital experience in the

last yeiir of life, medical care during pregnancy, health insurance coverage, etc.

For a list of titles of reports published in these series, write to: Scientific and Technical Information Branch

National Center for Health Statistics

Public Health Service, HRA

Rockville, Md. 20852