Series 13, Number 164 January 2007

Characteristics of

Office-Based Physicians

and Their Practices:

United States, 2003–04
Copyright information

All material appearing in this report is in the public domain and may be

reproduced or copied without permission; citation as to source, however, is

appreciated.

Suggested citation

Hing E, Burt CW. Characteristics of office-based physicians and their practices:

United States, 2003–04. Series 13, No. 164. Hyattsville, MD: National Center

for Health Statistics. 2007.

Library of Congress Cataloging-in-Publication Data

Characteristics of office-based physicians and their practices : United States,

2003–04.

p. ; cm. — (DHHS publication; no. (PHS) 2007–1735) (Vital and health

statistics. Series 13, Data from the National Health Care Survey; no. 164)

Includes bibliographical references.

ISBN 0–8406–0611–7

1. Physician practice patterns—United States—Statistics. 2. Ambulatory medical

care—United States—Statistics. 3. Primary care (Medicine)—United States—

States. I. Series. II. Series: Vital and health statistics. Series 13, Data from the

National Health Survey; no. 164.

[DNLM: 1. Physician’s Practice Patterns—United States—Statistics. 2.

Ambulatory Care—United States—Statistics. 3. Physician’s Office—United

States—Statistics. 4. Practice Management, Medical—United States—Statistics.

W2 A N148vm no.164 2006]

RA399.A3C485 2006

362.17’20973—dc22

2006029856

For sale by the U.S. Government Printing Office

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Printed on acid-free paper.
National Center for Health Statistics

Edward J. Sondik, Ph.D., Director

Jennifer H. Madans, Ph.D., Acting Co-Deputy Director

Michael H. Sadagursky, Acting Co-Deputy Director

Jennifer H. Madans, Ph.D., Associate Director for Science

Jennifer H. Madans, Ph.D., Acting Associate Director for

Planning, Budget, and Legislation

Michael H. Sadagursky, Associate Director for

Management and Operations

Lawrence H. Cox, Ph.D., Associate Director for Research

and Methodology

Margot A. Palmer, Director for Information Technology

Margot A. Palmer, Acting Director for Information Services

Linda T. Bilheimer, Ph.D., Associate Director for Analysis

and Epidemiology

Charles J. Rothwell, M.S., Director for Vital Statistics

Jane E. Sisk, Ph.D., Director for Health Care Statistics

Jane F. Gentleman, Ph.D., Director for Health Interview

Statistics

Clifford L. Johnson, Director for Health and Nutrition

Examination Surveys

Division of Health Care Statistics

Jane E. Sisk, Ph.D., Director

Robin Remsburg, Dr.N., Deputy Director

Catharine W. Burt, Ed.D., Chief, Ambulatory Care Statistics

Branch

Charles Adams, Chief, Technical Services Branch
Contents

Abstract ................................................................................................ 1

Introduction ............................................................................................. 1

Data Highlights .......................................................................................... 1

Methods ................................................................................................ 2

Results ................................................................................................... 3

Physician Characteristics................................................................................... 3

Physician Supply and Utilization ............................................................................ 3

Practice Characteristics .................................................................................... 4

Revenues and Access ..................................................................................... 5

Patient Encounters........................................................................................ 6

Discussion ................................................................................................ 7

References ................................................................................................ 9

Appendix I............................................................................................... 21

Technical Notes ......................................................................................... 21

Appendix II ............................................................................................. 29

Definition of Terms...................................................................................... 29

Appendix III ............................................................................................. 31

Excerpts from the 2004 Physician Induction Interview form ..................................................... 31

Figures

1. Percent distribution of sample physicians by in-scope status: National Ambulatory Medical Care Survey, 2003–04 ..... 2

2. Percent of office-based physicians who are female, by age: United States, 2003–04 .............................. 3

3. Percent of office-based physicians who are graduates of a foreign medical school, by age: United States, 2003–04 ..... 4

4. Average annual number of visits per physician, by location of physician: United States, 2001–02 and 2003–04 ........ 4

5. Percent of office-based physicians in practice-based research networks, by practice size: United States, 2003–04....... 5

6. Percent of office-based physicians using electronic medical records, by specialty: United States, 2003–04 ............ 5

7. Percent of office-based physicians not accepting new patients, by payment method: United States, 2003–04........... 6

8. Percent distribution of hospital visits made by office-based physicians, according to specialty: United States, 2003–04 . . 7

9. Number of managed care contracts as a function of mean weekly office volume and mean visit duration: United States,

2003–04............................................................................................ 7

Detailed Tables

1. Number and percent distribution of office-based physicians with corresponding standard errors, by selected

characteristics: United States, 2003–04 .................................................................. 11

2. Percentage with corresponding standard error of office-based physicians who are female or graduates of a

foreign medical school, by age, specialty type, and physician specialty: United States, 2003–04.................... 12

3. Number of office-based physicians with corresponding standard errors, by specialty type and geographic

characteristics: United States, 2003–04 .................................................................. 13

4. Number of physicians per 100,000 population with corresponding standard errors, by physician specialty and

geographic characteristics of physicians: United States, 2003–04 ............................................. 14

iii
5. Number, standard error, percent distribution, and mean percent of office-based physicians by selected practice

characteristics, according to specialty type: United States, 2003–04........................................... 15

6. Percentage with corresponding standard error of office-based physicians by specialty type and physician

accessibility: United States, 2003–04 ................................................................... 17

7. Mean number, percentage, and standad errors of patient encounters during the last full week of practice, by

physician’s specialty and type of patient encounter: United States, 2003–04 .................................... 18

8. Average number of weekly consultations per physician during last full week of practice with corresponding

standard errors, by type of encounter and practice characteristics: United States, 2003–04 ........................ 19

9. Average number of weekly consultations per physician during last full week of practice with corresponding

standard errors, by type of encounter and physician specialty: United States, 2003–04 ........................... 20

Appendix Tables

I. Average number of physicians in the universe, total sample, sample response categories, for the Physician Induction

Interview, and unweighted response rate by physician stratum: National Ambulatory Medical Care Survey, 2003–04. . . 21

II. Reasons sampled physicians were out of scope for the 2003–04 National Ambulatory Medical Care Survey.......... 22

III. Characteristics of the 2003–04 National Ambulatory Medical Care Survey, physician respondents and nonrespondents

to the Physician Induction Interview ................................................................... 24

IV. Weighted item nonresponse rates for report variables...................................................... 25

V. Reclassification of Physician Specialty Strata based on the American Medical Association specialty designations for

use in the National Ambulatory Medical Care Survey ...................................................... 26

VI. Reclassification of physician specialty into specialty type for use in the National Ambulatory Medical Medical Care

Survey ............................................................................................ 28

iv
Objective

This report presents demographic

and practice characteristics of

nonfederal physicians who were

primarily engaged in office-based

patient care in the United States during

2003–04.

Methods

The data in this report were

collected during the physician induction

interview for the 2003 and 2004

National Ambulatory Medical Care

Surveys (NAMCS). NAMCS includes a

national probability sample of

nonfederal office-based physicians who

saw patients in an office setting. It

excludes physicians in the specialties of

anesthesiology, radiology, and

pathology, as well as physicians

practicing in hospitals, institutions, and

occupational settings. Sample data

were weighted to produce national

estimates of the number of physicians

and characteristics of their practices.

Results

During 2003–04, an average annual

of 311,200 office-based physicians

provided patient care in the United

States, an overall rate of 108.4

physicians per 100,000 persons.

Approximately three-fourths of

office-based physicians owned or were

part owner of their practice, two-thirds

of physicians worked in group practices

with two or more physicians, and

one-half of office-based physicians

were primary care specialists.

Physicians with 10 or more managed

care contracts spent less time per

patient visit, but had more weekly visits

compared with physicians with fewer

than three managed care contracts.

The average total weekly number of

encounters (consults or visits) and the

average number of office visits per

physician were greater among primary

care specialists compared with other

specialty types. About one-fourth of

physicians (25.5 percent), reported that

they did not accept new Medicaid

patients and 13.9 percent did not

accept new Medicare patients—similar

to previous years.

Keywords: ambulatory care c work

force c physician supply

Characteristics of Office-Based

Physicians and Their Practices:

United States, 2003–04

by Esther Hing, M.P.H., and Catharine W. Burt, Ed.D., Division of

Health Care Statistics

Introduction

Physician offices are the settings

most frequently used for health

care, including the delivery of

primary and specialty care (1).

Describing the characteristics of

physicians providing this care and

factors influencing the care provided is

integral to monitoring the health of the

U.S. population and planning for future

health care delivery needs. The National

Ambulatory Medical Care Survey

(NAMCS), which began in 1973,

collects data on the utilization of

ambulatory medical care services

provided by nonfederal office-based

physicians. It was conducted annually

until 1981, again in 1985, and resumed

an annual schedule in 1989.

This report presents estimates of

physician practice and encounter

characteristics based on data collected

during the physician induction

interviews of the 2003–04 NAMCS. The

information complements data on

utilization of ambulatory medical care

services provided by office-based

physicians (2,3) by describing

characteristics of the physicians

providing care. The physician practice

characteristics described in this report

include size of practice, ownership,

revenue sources, use of information

technology, weekly workload, and

willingness to accept new patients. This

is the first of a series of reports on

characteristics of office-based physicians

that will permit tracking of physician

practice characteristics in more detail

than previously reported (4–6). It should

be noted that due to the scope of

NAMCS, physicians studied in this

report represent a subset of all

physicians (See Appendix I for details).

Data Highlights

+ Since 2001–02, the ratio of

office-based physicians to population

has not changed. The annual volume

of visits per physician, however,

decreased by 6%. Most of the

decrease occurred in the Northeast

(15%) and in metropolitan statistical

areas (MSAs) (7%).

+ Approximately three-fourths of

office-based physicians owned or

were part owner of their practice

(74.9 percent).

+ Two-thirds of physicians worked in

group practices with two or more

physicians.

+ In 2003–04, 35.8 percent of

physicians were in solo practices,

43.1 percent were in single-specialty

group practices, and 21.1 percent

were in multi-specialty group

practices.

+ Physicians with 11 or more managed

care contracts had 26 percent more

weekly office visits, but spent 18

percent less time on average with

each patient compared with

physicians with 1-2 managed care

contracts.

+ In 2003–04, 25.5 percent of

office-based physicians did not

accept new Medicaid patients, and

13.9 percent did not accept new

Medicare patients.

+ In 2003–04, office-based physicians

reported an average of 73.7 office

visits, 12.7 hospital visits, and 11.1

Page 1
telephone consultations during their

last full week of practice.

+ About one out of five physicians

(19.0 percent) reported using

electronic medical records (EMRs).

Methods

NAMCS is an annual national

probability sample survey of

visits to the offices of physicians

classified by the American Medical

Association (AMA) and American

Osteopathic Association (AOA) as

primarily engaged in ‘‘office-based

patient care.’’ Federally employed

physicians; those who specialize in

anesthesiology, radiology, or pathology;

and physicians who do not see patients

in an office, such as the majority of

emergency medicine physicians, are

excluded. NAMCS physician estimates

are roughly two-thirds the average

number of physicians (486,427) found

in the 2003 (483,025) and 2004

(489,829) combined AMA and AOA

master files of nonfederal office-based

physicians primarily engaged in patient

care (7,8), which is used as the

sampling frame for NAMCS. When

contacted, one-third of sampled

physicians were found to be ineligible

because they were out of scope as listed

above (11.3 percent), retired or deceased

(9.5 percent), practiced in a nonoffice

setting such as an institution or

occupational setting (4.7 percent), not

practicing (4.4 percent), or were

otherwise ineligible (3.9 percent)

(Figure 1).

NAMCS utilizes a multistage

probability sample design involving

samples of 112 geographic primary

sampling units (PSUs), physicians

stratified by specialty within PSUs, and

patient visits within physician practices.

PSUs are counties, groups of counties,

county equivalents (such as parishes or

independent cities), or towns and

townships for some PSUs in New

England.

Of 6,000 physicians sampled in

2003–04, 3,968 (66.1 percent) were

found to be eligible for the survey (2,3).

Data presented in this report are based

on physician responses to the Physician

Induction Interview (PII) questionnaire

(see Appendix III for excerpts of the

PII). Two years of data were analyzed to

improve the precision of the estimates.

During 2003–04, 2,235 of the eligible

physicians responded to the PII, for an

unweighted response rate of

56.3 percent. Sampling weights,

reflecting the multistage sample of

physicians, and nonresponse adjustments

were used to make average annual

national estimates of physicians.

Because the sampling frame is frozen at

the time of sample selection, the

estimator includes a calibration ratio that

adjusts the physician count in the frame

to match final AMA and AOA counts

for the survey year. See Appendix I for

more information on estimation,

response rates, and survey definitions.

The PII questionnaire included

questions used to determine physician

eligibility for the survey as well as to

gather information about the practice

such as size, ownership, and revenue

source (see Appendix II for definitions

of selected variables). Some

characteristics of physicians were taken

from the master files of the AMA and

AOA. These include age, sex, race and

ethnicity, foreign medical school

graduate, and specialty.

Many of the tables present estimates

by physician specialty. Two methods of

categorizing physician specialty are

provided. The first method was 13

major specialties, and the second used

three broad types of specialty (primary

care, surgical, and medical specialties).

See Appendix I for definitions. Both

methods are based on the specific

physician self-designated subspecialty

codes provided by the AMA and AOA

on the sampling frame and updated by

the physician during the NAMCS

induction interview.

Because estimates presented in this

report are based on sample surveys

rather than the universe of office-based

physicians, they are subject to sampling

variability. Appendix I includes an

explanation of the sampling errors with

guidelines for judging the precision of

the estimates and information on

physician and item nonresponse. The

standard errors were calculated using

Taylor series approximations in

SUDAAN, which take into account the

complex sample design of NAMCS (9).

In this report, estimates are not

presented if they are based on fewer

than 20 physicians in the sample data;

only an asterisk (*) appears in the

tables. Estimates based on 30 or more

physicians but with a standard error that

is more than 30 percent of the estimate

have an asterisk to indicate that they do

not meet the reliability standard set by

NCHS; estimates based on 20–29

physicians are also considered unreliable

and are presented with asterisks. In this

report, percentages based on categorical

responses were computed with missing

data (‘‘unknown’’ or ‘‘blank’’) in the

denominator so that responses represent

all physicians. This method, however, may

understate percentages if the distribution

among unknowns is similar to the

distribution among responses (see

Out-of-scope reasons

In scope

66.1%

Out of scope

33.9%

11.3%

9.5%

4.7%

4.4%

3.9%

Hospital-based, radiologist, 

anesthesiologist, 

pathologist, or 

federally employed

Retired or deceased

Nonoffice-based

Not practicing

Other ineligible

In-scope status

Figure 1. Percent distribution of sample physicians by in-scope status: National

Ambulatory Medical Care Survey, 2003–04

Page 2 [ Series 13, No. 164
Appendix I for information on missing

data for characteristics presented in the

report).

Chi-square tests using SUDAAN

were performed to detect significant

associations between provider

characteristics. All other tests of

statistical significance between two

estimates are based on the two-tailed

t-test at the 0.05 level of significance,

unless otherwise noted. Terms relating

to differences such as ‘‘greater than’’ or

‘‘less than’’ indicate that the difference

is statistically significant. A lack of

comment regarding the difference

between any two estimates does not

mean that the difference was tested and

found to be not significant.

The U.S. Census Bureau is the data

collection agent for NAMCS, and the

data are centrally processed by Constella

Group, Inc. There was 100 percent

independent keying of the 2003–04

induction forms, with a quality control

error rate of 0.1 percent. More

information about the data collection

procedures and survey background may

be found elsewhere (2,3).

Several tables in this report present

rates of physicians per population. The

population figures used in calculating

these rates are based on Census Bureau

monthly postcensal estimates of the

civilian noninstitutional population of

the United States as of July 1, 2003, and

July 1, 2004. These population estimates

are available from the U.S. Census

Bureau. See Appendix I for more

information.

Table 3 presents the annual number

of office visits per physician. The

numerator is the weighted number of

office visits estimated from NAMCS.

Each participating physician was asked

to provide information for a systematic

sample of office encounters during a

randomly selected 1-week reporting period.

Data from these encounters were weighted

to reflect national annual estimates.

Results

Physician characteristics

During 2003–04, 311,200

office-based physicians, on average,

were in practice on any given week in

the United States. Table 1 provides

national estimates of office-based

physicians by characteristics available

from the sampling frame. One-third of

physicians (34.1 percent) were 45–54

years of age at the time of the survey;

the mean age was 50.3 years. The

distribution of physicians by race and

ethnicity is presented in Table 1. These

data should be viewed with caution,

however, because item nonresponse for

physician race or ethnicity was

29 percent.

About one-half of physicians

practiced in primary care specialties

(49.5 percent). About 27.8 percent of

physicians were in medical specialties,

and 22.7 percent were in surgical

specialties. Specialties with the most

physicians include general and family

practice (17.6 percent), internal medicine

(15.6 percent), pediatrics (9.0 percent),

and obstetrics and gynecology

(7.8 percent).

About one in five office-based

physicians (22.2 percent) were female

(Table 1). The percentage of physicians

that were female decreased with

physician age (Figure 2). Nearly

one-half of office-based physicians

under 35 years of age were female

(47.8 percent) (Table 2). Females made

up a larger proportion of physicians in

pediatrics (50.3 percent) than in the

other specialties.

During 2003–04, 21.9 percent of

office-based physicians were graduates

of medical schools outside the United

States (Table 2). The percentage of

physicians that graduated from foreign

medical schools increased with age

among physicians under 65 years

(Figure 3). Graduates of foreign medical

schools made up a larger proportion of

physicians in primary care specialties

(23.7 percent) and medical specialties

(24.8 percent) than in surgical specialties

(14.5 percent).

Physician Supply and

Utilization

During 2003–04, the supply of

nonfederal office-based physicians per

population was 108.4 per 100,000

persons (Table 3). The overall ratio of

physicians per 100,000 population and

primary care specialists per 100,000

population were each greater in the

Northeast than in the South and West

regions. The overall visit load (annual

visits per provider), however, was higher

in the South (3,300 visits per physician)

than in the other regions of the country

(2,699–2,742 visits per physician). A

similar pattern occurred among primary

care specialists; the visit load for these

physicians was higher in the South

(3,976 per physician) than in the other

regions (3,045–3,321 per physician).

0

10

20

30

40

50

60

Under 35 35–44 45–54 55–64 65 and over

Physician age (years)

47.8

35.5

21.8

9.3

5.9 *

* Figure does not meet standard of reliability or precision. Percent of physicians

Figure 2. Percentage of office-based physicians who are female, by age: United States,

2003–04

Series 13, No. 164 [ Page 3
During 2003–04, there were more

nonfederal office-based physicians per

population in MSAs (114.2 per 100,000

persons) than in non-MSAs (78.4 per

100,000 persons). Although physicians

in primary care specialties were equally

distributed per population in MSAs

(54.9 per 100,000 persons) and

non-MSAs (47.0 per 100,000 persons),

the rate of medical specialists in

non-MSAs (12.4 per 100,000 persons)

was less than one-half the rate in MSAs

(33.6 physicians per 100,000 persons).

The visit load was equivalent for

physicians in MSAs and non-MSAs

regardless of whether the physician was

engaged in primary care, surgical

specialties, or medical specialties.

Table 4 shows physician-topopulation ratios by physician specialty

and location of the physician. With the

exception of the ‘‘All other’’ specialties

category, the physician-to-population

ratio was greater among general and

family practice physicians (19.1 per

100,000 persons) and internal medicine

physicians (16.9 per 100,000 persons)

than among the remaining specialties

(2.1–9.8 per 100,000 persons).

Between 2001–02 and 2003–04, the

ratio of nonfederal office-based

physicians to population remained

constant (between 105.4 and 108.4

physicians per 100,000 persons). The

visit load per physician decreased by

6% (Figure 4), from 3,102 visits per

physician in 2001–02 to 2,919 visits per

physician in 2003–04. Most of the

decreased visit volume per physician

occurred in the Northeast (down by

15%), specifically among primary care

specialties in this region (down by 18%,

data not shown). Between 2001–02 and

2003–04, the visit volume per physician

decreased in MSAs (down by 7%); most

of this decrease occurred among medical

specialists within MSAs (down by 13%,

data not shown).

Practice Characteristics

About one-third of the physicians

were in solo practices (35.8 percent),

about one-half were in practices with 2

to 10 physicians (53.5 percent), and

10.7 percent were in practices with 11 or

more physicians (Table 5). About

two-fifths of physicians (43.1 percent)

were in single-specialty group practices

with two or more physicians, and

21.1 percent were in multispecialty

group practices. The majority of

physicians were the owners or part

owners of their practices (74.9 percent).

Primary care specialists (28.1 percent)

were employees more frequently than

medical (17.2 percent) or surgical

specialists (14.7 percent) (Table 5).

Another practice characteristic

collected in the NAMCS induction

interview was whether the physician

participated in a practice-based research

network (PBRN), a consortium of

primary care physicians or providers

joining together for research purposes

(10). Providers join these networks to

investigate questions related to

community-based practice and to

improve the delivery and quality of

primary care. In 2004, there were more

0

10

20

30

40

Under 35 35–44 45–54 55–64 65 and over

Percent of physicians

Physician age (years)

* Figure does not meet standard of reliability or precision.

17.2

21.6

29.0

23.5

12.4 *

Figure 3. Percentage of office-based physicians who are graduates of a foreign medical

school, by age: United States, 2003–04

2003–04

2001–02

1Difference between 2001–02 and 2003–04 is statistically significant (p<0.05).

Average annual visits per physician

3,102

2,919

3,156

2,943

2,736

3,410

3,300

2,791

2,742

3,098

2,889

3,125

3,154

Geographic region

Metropolitan status

2,699

0 1,000 2,000 3,000 4,000

Total1

Non-MSA2

MSA1,2

West

South

Midwest

Northeast1

2 MSA is metropolitan statistical area.

Figure 4. Average annual number of visits per physician, by location of physician:

United States, 2001–02 and 2003–04

Page 4 [ Series 13, No. 164
than 110 PBRNs in the United States,

some of which have been in existence

for more than 20 years (10). In

2003–04, 6.0 percent of physicians

participated in PBRNs. Although the

percentage participating did not vary by

specialty type, the likelihood of

physician participation increased with

practice size (Figure 5).

The NAMCS induction interview

also asked about types of information

technology used by physicians. In

2003–04, the most frequent technology

used by office-based physicians was

electronic billing records (74.2 percent),

followed by electronic medical records

(19.0 percent) and a computerized

prescription order entry (CPOE) system

to fill prescriptions (9.2 percent).

Although the 2003–04 percentage of

physicians using electronic medical

records appears to have increased

slightly since 2001–02 (17.7 percent),

the difference was not statistically

significant (p = 0.76). Figure 6 presents

use of electronic medical records by

physician specialty in 2003–04. Use was

greater among primary care specialties

(11.8 percent) than among surgical

(6.4 percent) or medical specialties

(7.0 percent). Physicians in practices

using CPOE reported 80.4 percent of

prescriptions were written using this

technology.

Revenues and Access

During 2003–04, 86.3 percent of

physicians reported having at least one

managed care contract and 9.8 percent

reported having none. This information

was missing for 3.9 percent of

physicians (Table 5). About 40 percent

of physicians reported having between 3

and 10 managed care contracts, and

36.1 percent reported 10 or more

contracts. Of practices reporting at least

one managed care contract, the mean

percentage of revenue from these

contracts was 44.7 percent. The mean

percentage of revenue from managed

care contracts was higher among

primary care specialists (50.8 percent)

than among surgical (38.6 percent) or

medical (39.1 percent) specialists.

The NAMCS physician induction

interview included questions about the

percentage of practice revenue from

various payment sources (Table 5).

Among physicians reporting this

information, private insurance accounted

for about one-half of office revenue (on

average, 46.7 percent) and Medicare

accounted for an average of 31.1 percent

of revenue. Primary care specialists

reported a higher mean percentage of

revenue from private insurance

(51.1 percent) and Medicaid

(16.3 percent) than surgical or medical

specialists (Table 5). The mean

percentage of Medicare revenues,

however, was higher among surgical

(39.0 percent) and medical

(36.0 percent) specialists than among

primary care specialists (24.7 percent).

When physicians were asked if they

were currently accepting ‘‘new’’ patients

into their practice, 96 percent responded

positively (Table 6). Responses varied,

however, when physicians were asked

which payment sources they accepted

from new patients (47.7–91.0 percent).

Figure 7 presents the percentage of

physicians who reported what payment

sources they would not accept from new

patients. Approximately 40.3 percent of

Percent of physicians

NOTE: Linear trend by practice size is significant (p<0.01).

0 3 6 9 12 15

All physicians

11 or more

6–10

3–5

Partner

Solo

Practice size

2.7

4.8

5.8

9.5

14.2

6.0

Figure 5. Percentage of office-based physicians in practice-based research networks, by

practice size: United States, 2003–04

0 5 10 15 20 25 30

Psychiatry

Dermatology

Obstetrics and gynecology

Opthalmology

General surgery

Urology

Internal medicine

Pediatrics

Neurology

General and family practice

Orthopedic surgery

All other specialties

Otolaryngology

Cardiovascular diseases

Percent of physicians

27.2

24.4

21.6

21.6

20.2

10.1

19.7

18.2

18.2

17.3

17.3

17.2

15.5

12.5

Figure 6. Percentage of office-based physicians using electronic medical records, by

specialty: United States, 2003–04

Series 13, No. 164 [ Page 5
office-based physicians did not accept

new charity cases (as defined by no

charge or charity), 25.5 percent did not

accept new Medicaid cases, and

13.9 percent did not accept new

Medicare cases. Primary care specialists

were more likely not to accept new

Medicare cases (20.3 percent) compared

with either surgical specialists

(3.7 percent) or medical specialists

(10.8 percent). They were also less

likely to accept new Medicaid cases

(29.3 percent) than surgical specialists

(17.0 percent) (data not shown). For this

analysis, physicians who reported not

accepting any new patients, had

responses for each of the expected

payment sources edited to ‘‘no.’’ ‘‘No’’

responses may be understated if the

amount of missing data is large because

each percentage includes unknowns in

the denominator. The percentage with

missing data for these items ranged

from 3.0 for self-pay to 12.0 percent for

no charge or charity (see Appendix I for

further information).

Physicians also reported on

difficulty they had referring certain

types of patients for specialty care

(Table 6). Physicians had the least

difficulty referring Medicare and

privately insured patients. About

one-third had difficulty referring

Medicaid and uninsured patients.

Patient Encounters

Another practice characteristic

collected in the Physician Induction

Interview is the number of encounters

physicians had during their last full

week of practice prior to the interview

(Table 7). During 2003–04, the average

number of office visits reported was

73.8 visits per week, representing an 8%

decline since 2001 (3).

Other types of physician patient

encounters reported during the last full

week of practice included: hospital

visits, telephone consults, home visits,

and Internet e-mail consultations. During

2003–04, 69.7 percent of physicians

reported making at least one hospital

visit, 58.5 percent had at least one

telephone consultation, 10.6 percent

made one or more house visits

(including visits to nursing homes), and

5.5 percent reported having an e-mail or

Internet consultation during the week.

These recent estimates indicate declines

since 2001; the percentage of physicians

reporting hospital visits declined by

10%, telephone consultations declined

by 21%, and home visits declined by

40% (4).

During 2003–04, surgical specialists

were more likely to make a hospital

visit in their last full week of work

(78.5 percent) compared with other

types of specialties. However, the mean

number of visits for physicians who did

make hospital visits was about one-half

as much among surgical specialists (16.3

visits) as among medical specialists

(30.9 visits).

Some physicians may have provided

care in an emergency department (ED)

during their hospital visit. The

Emergency Medical Treatment and

Labor Act (EMTALA) of 1986 requires

hospitals accepting Medicare funding to

screen all patients presenting to the ED

for care and to stabilize emergency

medical conditions before transferring or

discharging patients from the ED (11).

In 2003–04, such care was provided by

22.8 percent of physicians during their

last full week of practice; at that time,

they provided, on average, 10.6 hours of

care (Table 7). Surgical specialists were

more likely to have provided EMTALA

care during the week (34.3 percent) than

were primary care (22.3 percent) or

medical care specialists (14.5 percent).

Office-based physicians provided a total

of 649,000 EMTALA hours per week in

local hospitals.

Table 8 shows the average weekly

number of consultations for all

physicians during their last full week of

practice, as well as those that occurred

during office visits, hospital visits, and

telephone consultations across practice

characteristics. To approximate total

volume of patient consultations made by

office-based physicians during their last

full week of practice, all types of

consultations—those conducted by

telephone, e-mail, or during any patient

visit occurring inside and outside of the

office (house or hospital visit)—were

summed, including those with no

encounters (Table 8). This is in contrast

to the data in Table 7, which excludes

doctors who reported no encounters.

In 2003–04, office-based physicians

had an average of 101.6 patient

encounters during their last full week of

work. This includes an average of 73.7

office visits, 12.7 hospital visits, 11.1

telephone consultations, 0.7 home visits,

and 0.5 e-mail consultations (last two

estimates not shown). The total volume

Percent of physicians

0 10 20 30 40 50

Self-pay

Noncapitated private insurance

Medicare

Medicaid

Worker's compensation

Capitated private insurance

No charge or charity

NOTE: See Appendix I for percentage missing for each payment method.

40.3

36.8

35.5

25.5

13.9

11.0

6.0

Figure 7. Percentage of office-based physicians not accepting new patients, by payment

method: United States, 2003–04

Page 6 [ Series 13, No. 164
of consultations was greater for primary

care specialists (114.7 encounters) than

for surgical and medical specialists

(85.6–90.4 encounters). However,

hospital visits were higher for medical

specialists (18.8 visits) than for primary

care and surgical specialists (9.4–12.8

visits). Office volume and total volume

increased with the number of managed

care contracts that physicians reported

(Table 8), driven by the positive

associations between office visit volume

and the number of contracts among

primary care and medical specialists

(data not shown).

Table 9 presents the average weekly

encounter volume by physician

specialty. Although dermatologists had

the highest average volume of office

visits, they had the lowest average

volume of hospital visits.

Figure 8 shows the percent

distribution of the estimated total annual

volume of hospital visits made by

office-based physicians (see Appendix I

for details). Although pediatricians

accounted for 11.6 percent of all office

visits, they made only 4.4 percent of

hospital visits. General and family

practice physicians accounted for

23.7 percent of office visits, but only

10.4 percent of hospital visits. The

largest share of hospital visits was made

by office-based physicians who are not

categorized among the leading 14

specialty groups used in NAMCS. The

high volume of hospital calls in the

residual ‘‘all other’’ specialty category is

driven by high volumes among

physicians specializing in

gastroenterology, nephrology, physical

medicine and rehabilitation, vascular

surgery, medical oncology, and

infectious diseases.

High office visit volume is

associated with shorter average visit

duration. Figure 9 shows the association

among office volume, visit duration (as

measured by the mean face-to-face

duration of their sampled patient visits),

and the number of managed care

contracts. As a group, physicians with

10 or more contracts had the highest

volume and shortest average duration,

whereas physicians with less than three

contracts had less volume, but higher

average duration.

Discussion

This report presents nationally

representative estimates of

office-based physicians who saw

patients during 2003–04, as well as

characteristics of their practices.

Although selected physician estimates

have been published previously (4–6),

the focus of those reports was patient

visits rather than the characteristics of

office-based physicians. This report is

the first to use NAMCS to focus on

physicians and the characteristics of

their practices. These data can be used

6.6

6.2

4.4

4.1

2.8

2.1

36.7

10.4

9.2

17.5

0 10 20 30 40

Urology

Neurology

Orthopedic surgery

Pediatrics

Obstetrics and gynecology

General surgery

Cardiovascular disease

General and family medicine

Internal medicine

Other specialties1

Percentage of hospital visits

1About four-fifths of hospital visits in this category were made by physicians specializing in either gastroenterology, 

nephrology, physical medicine and rehabilitation, vascular surgery, medical oncology, or infectious diseases.

NOTE: Based on a total estimated 142,312,000 visits made annually to patients in hospitals.

Figure 8. Percent distribution of hospital visits made by office-based physicians,

according to specialty: United States, 2003–04

Visit duration in minutes

NOTE: Each data point (centroid) represents the intersection between the mean visit duration and the mean weekly volume 

of office visits for physicians grouped by number of managed care contracts (None, 1–2, 3–10, 11 or more). 

11 or more 

3–10 

1–2

None

Weekly visits volume

0 20 25 30

0

65

70

75

80

Figure 9. Number of managed care contracts as a function of mean weekly volume of

office visits and mean visit duration: United States, 2003–04

Series 13, No. 164 [ Page 7
Page 8 [ Series 13, No. 164

to track trends on supply of office-based

physicians who actually see patients in

an office setting, patterns of care

provided, and organizational factors

affecting care.

One use of these data is the

tracking aspects of the quality of patient

care. The federal government, health

insurers, accrediting organizations, and

consumer groups have advocated

increased adoption of electronic medical

record (EMR) systems by physicians to

reduce medical errors and to improve

patient care (12). This study found that

in 2003–04, EMR use by physicians

(19.0 percent) was not widespread.

However, recent estimates from the

survey indicate EMR use by officebased physicians increased to

23.9 percent in 2005 (13). EMR

adoption could improve patient care by

reducing prescription errors due to

transcription errors, providing prevention

reminders to the physicians, and

providing the latest information on

evidence-based care for chronic

conditions (14) and on the quality of

their own clinical performance. A recent

study found that only one-third of

physicians had access to data to monitor

the quality of their clinical performance

(15). The current study also documented

physician participation (6 percent) in

practice-based research networks

(PBRN). Physicians join these networks

to understand and improve primary care

within a research environment. Recent

PBRN research supports quality

improvements and adoption of

evidence-based culture in primary care

practice (10).

As measured by the ratio of

physicians to population, the report

found no change in the overall supply of

office-based physicians between

2001–02 and 2003–04, although the

regional variation noted in previous

studies (6,16,17) persisted in 2003–04.

The stability in the overall supply of

physicians may be partly due to

international medical graduates who

emmigrated to the United States.

According to the AMA, international

medical graduates accounted for 29% of

the increase in office-based physicians

between 1980 and 2004 (18). This study

found that foreign medical school

graduates accounted for 21.9 percent of

office-based physicians in 2003–04. The

overall supply of physicians could have

also been affected by the availability of

mid-level providers (physician assistants,

nurse practitioners, nurse midwives, and

clinical nurse specialists) in physician

practices who may be potential

caregivers. The proportion of physicians

in noninstitutional practice settings

employing mid-level providers increased

from 40 percent in 1997 to 48 percent in

2001 (19).

As discussed earlier, because

NAMCS physician estimates are lower

than AMA and AOA physician

estimates, physician-to-population ratios

presented in this report are also lower

than ratios derived using AMA (18) and

AOA physician estimates. NAMCS

estimates are lower because one-third of

the sampled physicians were found to be

out of scope for NAMCS during the

induction interview (see Appendix I for

more details). Of physicians found to be

out of scope, one-half were ineligible

because the physician was in a

hospital-based specialty or was

classified as a radiologist,

anesthesiologist, or pathologist, was

federally employed, or worked in a

nonoffice based setting (Table II). The

remaining physicians were ineligible

because they were not practicing

medicine; they were retired, deceased,

worked as an administrator, moved,

couldn’t be located, or were otherwise

not seeing patients.

Although the overall ratio of

physicians to population did not change

between 2001–02 and 2003–04, the

annual visit volume per physician

decreased by 6%. Between 2001–02 and

2003–04, decreases in annual volume of

visits per physician occurred in the

Northeast (down by 15%), principally

among primary care specialists in this

region (down by 18%). Since 2001–02,

the visit volume per physician also

decreased among physicians located in

MSAs (down by 7%), principally among

medical specialists in this region (down

by 13%). In contrast to the decline in

visit volume per physician, the volume

of hospital emergency department (ED)

visits per operating ED increased by

78% between 1995 and 2003 (20), while

the visit volume to hospital outpatient

department clinics per operating OPD

remained constant since 1999 (data not

shown).

In addition to a decline in annual

volume of visits per physician since

2001–02, the report found that

physicians had fewer patient encounters

during their last complete week of

practice. Between 2001 and 2003–04,

the average number of office visits per

physician declined by 8%, the

percentage of physicians reporting

hospital visits declined by 10%, the

percentage reporting telephone

consultations declined by 21%, and the

percentage making home visits declined

by 40% (4). These data support previous

research indicating that physicians may

be reducing the number of hours they

work (21,22).

Two factors may be related to

physicians working fewer hours. First,

the pool of physicians is aging. In

2003–04, the median age of office-based

physicians was 50.3 years. With

one-half of office-based physicians 50

years of age and over, some physicians

may work fewer hours because they are

nearing retirement age. Second, the

proportion of female physicians is

increasing. According to the Association

of American Medical Colleges, the

percentage of female medical school

students increased by 77% between

1980–81 (26.5 percent) and 2002–03

(46.8 percent) (23). Female physicians

increased the most during that period in

office-based practices (up by 567%)

(18). Previous research found female

physicians generally work fewer hours

than male physicians (17,22,24). This

may partially explain the decrease in

total hours worked by physicians.

Another study concluded that an

observed trend of more pediatricians

working part-time (11% in 1993

compared with 15% in 2000) was likely

to continue because of the increasing

proportion of females in this specialty

(25). In 2003–04, half of all officebased pediatricians were women

(Table 2).

The report found that the number of

patient visits made to physicians was

associated with the number of managed

care contracts the physician had. In

2003–04, physicians with 10 or more

managed care contracts spent less time

per patient visit, but had more weekly
Series 13, No. 164 [ Page 9

visits than physicians with fewer than

three managed care contracts. In

contrast, physicians with fewer than

three managed care contracts spent more

time with their patients and had fewer

weekly visits. This finding is consistent

with previous research, which found that

a majority of physicians in managedcare systems (75 percent) felt pressure to

see more patients per day (26). In

2003–04, a higher percentage of primary

care specialists’ revenue (50.8 percent)

came from managed care contracts than

from surgical (38.6 percent) and medical

specialists (39.1 percent). Although it is

unclear whether a shorter visit duration

results in lower quality of care or less

patient satisfaction, the previous study

found that physicians with managed care

incentives tied to productivity believed

that pressure to see more patients per

day compromised care (26). It is also

possible that shorter visits associated

with physicians with many managed

care contracts may have occurred

because substitution of mid-level

providers and use of disease

management programs are more

frequent among physicians with

managed care contracts. Unpublished

visit data from NAMCS indicates that

use of physician assistants and nurse

practitioners increases with the number

of managed care contracts physicians

had (data not shown).

Finally, although physicians

reported seeing fewer patients per week

in 2003–04 compared with 2001, time

spent by physicians in nonpatient care

activities may be increasing. A previous

study found that nearly one-half of a

primary care physician’s work day was

spent on followup and documentation of

patient care occurring outside of time

spent in the face-to-face patient

encounter (27). Although new

technologies such as electronic medical

records and computerized physician

order entry systems have the potential to

make physicians more productive by

reducing time spent documenting care

(28), they may also increase the time

spent by physicians during the initial

implementation phase (29).

As the previous discussion

illustrates, data presented in this report

can be used to track multiple issues

affecting the supply and practice

characteristics of office-based

physicians. The NAMCS physician

interview data can also be used to

examine patient care decisions made by

medical practices, such as adoption of

evidence-based guidelines or use of

electronic medical records, based on

derived medical practice estimates (30).

The data also provide estimates of

terrorism training and preparedness for

office-based physicians and their staff

(physician assistants, nurse practitioners

and nurses) (31).

Additional information about

office-based physicians is available from

the NCHS Ambulatory Health Care

website at http://www.cdc.gov/nchs/

about/major/ahcd/ahcd1.htm. Data from

the 2003–04 NAMCS PII are available

through the NCHS Research Data

Center. Queries regarding NAMCS data

may be sent to NCHS at

nchsquery@cdc.gov.

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hitframework.pdf .

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Schoenbaum SC. Measure, learn, and

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Series 13, No. 164 [ Page 11

Table 1. Number and percent distribution of office-based physicians with corresponding standard errors, by selected characteristics:

United States, 2003–04

Number of Standard Percent Standard

Selected characteristics1 physicians2 error distribution error

Total ......................... 311,200 8,000 100.0 . . .

Age

Under 35 years ................... 14,300 1,900 4.6 0.6

35–44 years ..................... 86,000 4,300 27.6 1.3

45–54 years ..................... 106,200 4,700 34.1 1.3

55–64 years ..................... 75,300 4,500 24.2 1.2

65 years and over ................. 29,400 2,600 9.4 0.8

Sex

Male .......................... 242,000 7,400 77.8 1.1

Female ........................ 69,200 1,900 22.2 1.1

Race and ethnicity

White, not Hispanic ................. 176,900 6,800 56.9 1.4

Asian or Pacific Islander.............. 28,100 3,000 9.0 0.9

Black, not Hispanic ................. 8,000 1,300 2.6 0.4

Hispanic........................ 7,800 1,600 2.5 0.5

Other or unknown.................. 90,300 4,300 29.0 1.2

Graduate of foreign medical school

No ........................... 225,200 7,600 72.4 1.3

Yes........................... 68,300 4,200 21.9 1.3

Unknown ....................... 17,700 1,400 5.7 0.5

Specialty type3

Primary care ..................... 153,900 4,600 49.5 1.1

Medical ........................ 86,600 4,400 27.8 1.1

Surgical ........................ 70,600 3,400 22.7 0.9

Physician specialty4

General and family practice............ 54,800 2,500 17.6 0.8

Internal medicine .................. 48,400 2,800 15.6 0.8

Pediatrics ....................... 28,100 1,700 9.0 0.5

Obstetrics and gynecology ............ 24,200 1,700 7.8 0.5

Psychiatry ...................... 18,000 1,000 5.8 0.3

Orthopedic surgery ................. 15,400 1,300 4.9 0.4

Cardiovascular diseases.............. 14,000 1,000 4.5 0.3

Ophthalmology.................... 12,700 900 4.1 0.3

General surgery ................... 12,300 800 3.9 0.3

Urology ........................ 6,800 400 2.2 0.1

Dermatology ..................... 6,800 300 2.2 0.1

Otolaryngology.................... 6,300 400 2.0 0.1

Neurology....................... 6,200 400 2.0 0.1

All other specialties ................. 57,200 3,800 18.4 1.0

...Not applicable.

1

Characteristic information is from the master files of the American Medical Association and the American Osteopathic Association.

2

Average number of nonfederal office-based physicians during 2003–04, excluding the specialties of radiology, pathology, and anesthesiology. Estimates were rounded to the nearest hundred.

3

Specialty type is defined in Table VI.

4

Physician specialty is defined in Table V.

NOTE: Numbers may not add to totals because of rounding. Figures are annual averages.
Page 12 [ Series 13, No. 164

Table 2. Percentage with corresponding standard error of office-based physicians who are female or graduates of a foreign medical school,

by age, specialty type, and physician specialty: United States, 2003–04

Selected characteristics1 Female Graduate of foreign medical school

Percent

Standard

error Percent

Standard

error

Total ......................... 22.2 1.1 21.9 1.3

Age

Under 35 years ...................

35–44 years .....................

45–54 years .....................

55–64 years .....................

65 years and over .................

Specialty type2

Primary care .....................

Medical ........................

Surgical ........................

Physician specialty3

Pediatrics .......................

Obstetrics and gynecology ............

Psychiatry ......................

Internal medicine ..................

Dermatology .....................

General and family practice............

Neurology.......................

Ophthalmology....................

Cardiovascular diseases..............

Otolaryngology....................

General surgery ...................

Orthopedic surgery .................

Urology ........................

All other specialties .................

47.8

35.5

21.8

9.3

*5.9

32.3

17.6

6.0

50.3

39.1

27.7

27.5

25.6

23.8

22.1

11.8

*9.6

*6.5

*6.0

*2.4

*1.0

11.7

6.5

2.5

2.0

1.5

2.0

1.9

2.0

1.1

3.9

4.7

3.8

4.0

4.5

2.3

4.0

3.3

3.3

2.3

2.3

1.4

0.7

2.5

*12.4

17.2

21.6

29.0

23.5

23.7

24.8

14.5

23.1

11.9

19.6

35.5

9.8

17.7

30.0

*7.8

28.4

12.6

17.2

11.9

25.1

25.4

4.1

2.1

2.3

2.7

3.5

1.9

2.3

1.6

3.4

3.4

3.4

4.3

2.8

2.4

4.1

2.5

4.3

2.8

3.0

2.8

3.7

3.2

* Figure does not meet standard of reliabiity or precision.

1

Characteristic information is from the master files of the American Medical Association and the American Osteopathic Association.

2

Specialty type is defined in Table VI.

3

Physician specialty is defined in Table V.
Series 13, No. 164 [ Page 13

Table 3. Number of office-based physicians with corresponding standard errors, by specialty type and geographic characteristics:

United States, 2003–04

Specialty type1

Geographic characteristic

All

specialties

Primary

care Surgical Medical

All

specialties

Primary

care Surgical Medical

Number of physicians Standard error

Total ..................... 311,200 153,900 70,600 86,600 8,000 4,600 3,400 4,400

Geographic region

Northeast ..................

Midwest ...................

South ....................

West .....................

66,600

69,400

105,000

70,200

33,500

35,200

50,200

34,900

14,900

15,800

24,400

15,500

18,100

18,300

30,400

19,800

4,000

3,300

5,600

2,300

1,900

2,800

3,000

1,600

1,500

1,900

1,900

1,200

1,700

1,700

3,100

1,700

Metropolitan status

MSA2 ....................

Non-MSA2 .................

275,000

36,200

132,200

21,700

61,900

8,800

80,900

5,700

7,600

5,100

4,000

3,000

3,000

1,900

4,400

1,300

Number of physicians per 100,000 persons3

Total ..................... 108.4 53.6 24.6 30.2 2.8 1.6 1.2 1.5

Geographic region

Northeast ..................

Midwest ...................

South ....................

West .....................

124.0

107.5

102.0

106.7

62.4

54.6

48.8

53.0

27.8

24.5

23.7

23.5

33.7

28.4

29.5

30.1

7.4

5.2

5.5

3.5

3.6

4.3

2.9

2.5

2.7

2.9

1.9

1.8

3.2

2.6

3.1

2.6

Metropolitan status

MSA2 ....................

Non-MSA2 .................

114.2

78.4

54.9

47.0

25.7

19.0

33.6

12.4

3.2

11.1

1.7

6.4

1.3

4.0

1.8

2.8

Number of physicians per county4

Total ..................... 99.0 48.9 22.5 27.6 2.6 1.5 1.1 1.4

Metropolitan status

MSA2 .................... 253.0 121.6 56.9 74.4 7.0 3.7 2.8 4.0

Non-MSA2 ................. 17.6 10.6 4.3 2.8 2.5 1.4 0.9 0.6

Number of annual office visits per physician5

Total ..................... 2,919 3,465 2,542 2,258 55 75 89 98

Geographic region

Northeast .................. 2,699 3,045 2,378 2,324 109 149 158 219

Midwest ................... 2,736 3,279 2,415 1,967 111 145 164 168

South .................... 3,300 3,976 2,807 2,577 110 144 188 200

West ..................... 2,742 3,321 2,414 1,978 88 155 145 147

Metropolitan status

MSA2 .................... 2,889 3,436 2,582 2,229 58 82 99 100

Non-MSA2 ................. 3,154 3,641 2,260 2,674 141 213 142 422

1

Specialty type is defined in Table VI.

2

MSA is metropolitan statistical area.

3

Regional population estimates are based on U.S. Census Bureau estimates of the civilian noninstitutionalized population of the United States as of July 1, 2003, and July 1, 2004. Metropolitan area

estimates are from the National Health Interview Survey with adjustments to match the 2003–04 population estimates obtained from the U.S. Census Bureau.

4

Based on 3,144 counties: 1,087 MSA counties and 2,057 non-MSA counties.

5

Rate is the 2003–04 annual average number of office visits divided by the 2003–04 average number of physicians.

NOTE: Numbers may not add to totals because of rounding. Figures are annual averages.
Page 14 [ Series 13, No. 164

Table 4. Number of physicians per 100,000 population with corresponding standard errors, by physican specialty and geographic

characteristics of physicians: United States. 2003–04

Geographic region Metropolitan status

Physican specialty1 Total Northeast Midwest South West MSA2 Not MSA2

Number of physicians per 100,000 population3

All specialties................ 108.4 124.0 107.5 102.0 106.7 114.2 78.4

General and family practice ....... 19.1 15.9 22.8 17.5 20.6 18.5 22.0

Internal medicine ............. 16.9 23.5 15.8 15.2 15.2 16.9 16.6

Pediatrics .................. 9.8 13.3 8.4 8.7 10.1 11.0 *

Obstetrics and gynecology ....... 8.4 9.5 8.0 8.8 7.5 9.2 *

Psychiatry.................. 6.3 8.3 5.2 5.7 6.5 6.8 *

Orthopedic surgery ............ 5.4 5.8 5.4 5.0 5.6 5.3 5.8

Cardiovascular diseases ......... 4.9 5.7 4.3 5.1 4.4 5.6 *

Ophthalmology ............... 4.4 5.3 4.1 4.1 4.6 4.8 *

General surgery .............. 4.3 4.5 4.8 4.2 3.6 4.0 5.5

Dermatology ................ 2.4 3.0 2.2 2.0 2.5 2.6 *

Urology ................... 2.4 2.7 2.4 2.4 2.0 2.5 *

Otolaryngology ............... 2.2 2.2 2.2 2.2 2.2 2.4 *

Neurology .................. 2.1 2.5 2.0 2.1 2.0 2.4 *

All other specialties ............ 19.9 21.8 19.8 19.1 19.8 22.1 8.8

Standard error

All specialties................ 2.8 7.4 5.2 5.5 3.5 3.2 11.1

General and family practice ....... 0.9 1.7 2.6 1.4 1.5 1.0 3.1

Internal medicine ............. 1.0 2.1 2.0 1.6 2.3 1.0 3.5

Pediatrics .................. 0.6 1.2 1.0 1.1 1.4 0.6 *

Obstetrics and gynecology ....... 0.6 1.6 1.0 1.1 1.2 0.7 *

Psychiatry.................. 0.4 1.4 0.4 0.4 0.7 0.4 *

Orthopedic surgery ............ 0.5 0.8 1.3 0.7 0.8 0.5 1.5

Cardiovascular diseases ......... 0.4 0.8 0.8 0.5 0.9 0.4 *

Ophthalmology ............... 0.3 0.6 0.6 0.7 0.6 0.4 *

General surgery .............. 0.3 0.7 0.5 0.6 0.5 0.3 1.1

Dermatology ................ 0.1 0.3 0.2 0.2 0.3 0.1 *

Urology ................... 0.1 0.3 0.3 0.3 0.2 0.2 *

Otolaryngology ............... 0.1 0.3 0.3 0.2 0.2 0.1 *

Neurology .................. 0.1 0.3 0.4 0.2 0.2 0.2 *

All other specialties ............ 1.3 2.0 2.5 2.8 2.1 1.5 2.9

* Figure does not meet standard of reliability or precision.

1

Physician specialty is defined in Table V.

2

MSA is metropolitan statistical area.

3

Regional population estimates are based on U.S. Census Bureau estimates of the civilian noninstitutionalized population of the United States as of July 1, 2003, and July 1, 2004. Metropolitan area

estimates are from the National Health Interview Survey with adjustments to match the 2003–04 population estimates obtained from the U.S. Census Bureau.
Series 13, No. 164 [ Page 15

Table 5. Number, standard error, percent distribution, and mean percent of office-based physicians by selected practice characteristics,

according to specialty type: United States, 2003–04

Specialty type1

Practice characteristics

All

specialties

Primary

care Surgical Medical

All

specialties

Primary

care Surgical Medical

Average number of physicians Standard error

All office-based physicians ............... 311,200 153,900 70,600 86,600 8,000 4,600 3,400 4,400

Percent distribution

All office-based physicians ............... 100.0 100.0 100.0 100.0 . . . . . . . . . . . .

Number of in-scope office locations

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

2 or more .........................

85.6

14.4

91.1

8.9

78.6

21.4

81.6

18.4

1.0

1.0

1.3

1.3

2.0

2.0

1.8

1.8

Practice size2

Solo.............................

Partner...........................

3–5 .............................

6–10 ............................

11 or more ........................

35.8

11.8

26.9

14.8

10.7

33.4

12.9

28.5

14.9

10.3

34.0

11.7

29.3

14.0

11.0

41.6

10.0

21.9

15.3

11.1

1.4

0.9

1.4

0.9

0.9

2.1

1.5

2.0

1.5

1.4

2.4

1.5

2.2

1.7

1.6

2.2

1.4

2.2

1.9

1.5

Solo and group practice

Solo............................. 35.8 33.4 34.0 41.6 1.4 2.1 2.4 2.2

Group practice:

Single-specialty practice ...............

Multispecialty practice ................

43.1

21.1

41.8

24.8

48.5

17.5

40.9

17.5

1.7

1.3

2.3

1.9

2.6

1.9

2.8

2.0

Employment status

Owner ...........................

Employee .........................

Contractor .........................

74.9

22.0

3.0

69.0

28.1

2.8

82.8

14.7

*

78.9

17.2

3.9

1.3

1.3

0.5

2.1

2.1

0.7

1.6

1.6

*

1.8

1.7

1.0

Ownership

Physician or group....................

Health maintenance organization ...........

Other ............................

85.7

2.0

12.3

80.2

2.9

16.9

93.2

1.1

5.7

89.5

1.2

9.4

1.2

0.4

1.1

1.9

0.8

1.7

1.2

0.4

1.1

1.5

0.4

1.4

Participates in practice-based

research network

Yes .............................

No..............................

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

6.0

81.9

12.1

5.9

80.6

13.5

5.0

84.8

10.2

7.1

81.8

11.1

1.0

1.3

0.9

1.2

1.8

1.4

1.3

1.9

1.4

1.6

1.9

1.6

Information technology3

Electronic billing records ................

Electronic medical records ...............

CPOE4 ...........................

74.2

19.0

9.2

76.0

18.4

11.8

76.0

19.7

6.4

68.1

19.5

7.0

1.2

1.3

1.0

1.9

1.8

1.5

2.0

2.3

1.3

2.1

2.2

1.2

Mean percent5

Percent of prescriptions written using CPOE4 . . . 80.4 82.9 80.3 73.7 2.7 3.4 4.5 6.0

Number of managed care contracts Percent distribution

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

None ............................

1–2 .............................

3–10 ............................

More than 10 .......................

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

100.0

9.8

11.2

39.1

36.1

3.9

100.0

8.7

11.6

40.4

35.6

3.6

100.0

7.8

10.0

38.9

39.5

3.7

100.0

13.4

11.3

36.8

34.0

4.6

. . .

0.9

1.0

1.7

1.8

0.7

. . .

1.3

1.5

2.3

2.4

0.8

. . .

1.4

1.4

2.4

2.6

1.0

. . .

1.4

1.3

2.6

2.5

1.1

See footnotes at end of table.
Page 16 [ Series 13, No. 164

Table 5. Number, standard error, percent distribution, and mean percent of office-based physicians by selected practice characteristics,

according to specialty type: United States, 2003–04—Con.

Specialty type1

Practice characteristics

All

specialties

Primary

care Surgical Medical

All

specialties

Primary

care Surgical Medical

Mean percent6

Percent of revenue from managed care

contracts ......................... 44.7 50.8 38.6 39.1 1.2 1.7 1.5 1.5

Percent of revenue from selected sources7 Mean percent Standard error

Private insurance .................... 46.7 51.1 41.4 43.3 0.8 1.2 1.2 1.2

Medicare.......................... 31.1 24.7 39.0 36.0 0.7 0.9 1.1 1.3

Medicaid .......................... 13.2 16.3 9.6 10.7 0.5 0.9 0.6 0.8

Other sources ...................... 9.4 8.3 10.1 10.8 0.6 0.7 1.0 1.3

...Data not applicable.

* Figure does not meet standards of reliability or precision.

1

Specialty type is defined in Table VI.

2

Practice size is number of physicians in practice.

3

The level of missing data was 8 percent for electronic billing records, 1 percent for electronic medical records, and 2 percent for CPOE.

4

CPOE is computerized prescription order entry system.

5

Mean percent of prescriptions written by physicians using CPOE. Information on prescriptions written was missing for 11 percent of physicians using CPOE.

6

Mean percent among physicians with any managed care revenue. Information on managed care revenue was missing for 21 percent of physicians with any managed care contract.

7

Mean percent of revenue among physicians. Sum will approximate a percent distribution, but responses were provided as a percentage for each source of revenue. Cases with missing data were

excluded (6–15 percent depending on type of payment source).
Series 13, No. 164 [ Page 17

Table 6. Percentage with corresponding standard error of office-based physicians by specialty type and physician accessibility: United

States, 2003–04

Specialty type1 Specialty type1

All Primary All Primary

Physician accessibility specialties care Surgical Medical specialties care Surgical Medical

Percent of physicians accepting new

patients by payment source2 Percent of physicians Standard error

Any new patients .................. 95.8 94.2 98.6 96.5 0.6 1.1 0.4 0.8

Self-pay ........................ 91.0 89.4 93.8 91.5 0.8 1.4 1.0 1.2

Medicare ....................... 83.0 75.6 94.1 86.9 1.0 1.7 1.2 1.5

Noncapitated private insurance ......... 79.1 79.5 82.9 75.1 1.2 1.7 1.8 2.0

Medicaid ....................... 70.4 66.4 79.6 69.9 1.3 2.1 2.0 2.2

Worker’s compensation .............. 57.9 50.8 80.6 52.2 1.6 2.1 1.9 2.9

Capitated private insurance ............ 52.8 58.8 47.4 46.4 1.7 2.4 2.8 2.7

No charge or charity ................ 47.7 44.5 53.6 48.5 1.8 2.5 2.9 2.6

Percent with difficulty referring certain types

of patients for specialty consultation3

Medicaid ....................... 32.0 37.6 26.2 26.8 1.5 2.2 2.2 2.1

Medicare ....................... 10.4 11.7 6.5 11.1 0.9 1.5 1.1 1.6

Private insurance .................. 14.2 15.3 10.9 14.8 1.1 1.6 1.4 2.0

Uninsured....................... 32.2 33.5 29.0 32.4 1.4 1.9 2.3 2.4

1

Specialty type is defined in Table VI.

2

Information on accepting any new patients was missing for 0.7 percent of cases. The level of missing data for each type of new patient accepted ranged from 3–12 percent depending on type of

payment source.

3

Difficulty refers to the practice experiencing some or a lot of difficulty in referring patients with various types of health insurance for specialty consultation in the last 12 months. The level of missing

data for each type of patient ranged from 13–22 percent depending on payment source.
Page 18 [ Series 13, No. 164

Table 7. Mean number, percentage, and standard errors of patient encounters during the last full week of practice, by physician’s specialty

and type of patient encounter: United States, 2003–04

Type of patient encounter

All

specialties

Specialty type1

Primary

care Surgical

Mean number in week2

Medical

All

specialties

Specialty type1

Primary

care Surgical

Standard error

Medical

Volume of office visits last full week . .

Type of consultation3

73.8 84.9 66.9

Percent of physicians4

59.6 1.3 1.8 2.3 2.6

Hospital visits ............... 69.7 68.5 78.5 64.7 1.3 2.1 1.9 2.1

Telephone consultation .......... 58.5 66.7 47.0 52.9 1.8 2.3 2.7 3.1

Home visits ................. 10.6 15.8 4.9 5.8 0.9 1.6 1.1 1.2

E-mail or Internet consultation ..... 5.5 6.3 4.7 4.9 1.0 1.2 1.5 1.3

EMTALA-mandated care5 ........ 22.8 22.3 34.3 14.5 1.3 2.2 2.3 1.6

Volume of consultations or visits3 Mean number in week6

Telephone consultation .......... 19.0 22.5 11.0 16.7 1.0 1.5 0.7 1.5

Hospital visits ............... 18.7 13.8 16.3 30.9 0.9 0.8 1.3 2.8

Home visits ................. 7.0 7.6 4.1 6.0 0.8 1.0 1.0 1.9

E-mail or Internet consultations..... 5.7 6.3 3.8 5.9 1.0 1.6 0.8 1.2

Hours of EMTALA-mandated care5 . . 10.6 11.6 10.6 8.1 1.1 1.9 1.2 1.0

1

Specialty type is defined in Table VI.

2

Mean number of office visits during last full week of practice among physicians with any visits.

3

Information on type of consultations was missing from 10–14 percent of cases, depending on type of consultation.

4

Percent of physicians reporting any consultations during last full week of practice with any of that type of consultation.

5

EMTALA is Emergency Medical Treatment and Labor Act of 1986.

6

Mean number of consultations during last full week of practice for physicians reporting any of that type of consultation.
Series 13, No. 164 [ Page 19

Table 8. Average number of weekly consultations per physician during last full week of practice with corresponding standard errors, by

type of encounter and practice characteristics: United States, 2003–04

Practice characteristic

Total

consultations1

Office

visits

Hospital

visits

Telephone

consultations

Total

consultations1

Office

visits

Hospital

visits

Telephone

consultations

Average number of consultations reported2 Standard error

All office-based physicians ....... 101.6 73.7 12.7 11.1 2.1 1.3 0.6 0.7

Specialty type3

Primary care................

Surgical ...................

Medical ...................

114.7

85.6

90.4

84.8

66.7

59.5

9.4

12.8

18.8

15.0

5.2

8.8

2.9

2.8

3.7

1.8

2.3

2.6

0.7

1.0

1.5

1.1

0.4

1.0

Practice size

Solo .....................

Partner....................

3–5 ......................

6–10 .....................

11 or more .................

100.0

108.7

105.4

98.6

93.7

72.1

80.8

77.9

70.5

64.5

11.2

11.9

14.3

13.5

14.1

11.7

10.4

11.3

11.5

8.7

3.8

5.3

3.5

3.7

4.8

2.6

3.7

2.3

2.9

2.6

1.0

1.7

1.4

1.4

1.5

1.1

1.4

1.3

1.3

2.0

Number of managed care contracts

None .....................

1–2 ......................

3–10 .....................

More than 10 ................

83.6

81.4

103.2

111.8

64.2

62.6

74.9

79.2

8.3

10.0

13.5

13.9

6.5

9.7

10.3

13.4

6.2

4.1

3.6

3.3

4.6

3.0

2.3

2.3

1.5

1.6

1.0

1.0

0.9

1.3

1.1

1.3

Ownership

Physician or group ............

Health maintenance organization....

Other.....................

102.6

94.6

96.3

74.2

70.7

70.5

13.2

6.8

10.5

11.1

12.9

11.0

2.3

5.9

4.7

1.5

6.1

2.8

0.7

2.0

1.6

0.8

2.7

1.6

Geographic region

Northeast ..................

Midwest ...................

South ....................

West .....................

101.6

99.5

111.9

88.8

67.7

74.8

81.8

65.9

11.5

13.9

15.5

8.4

15.9

9.0

9.9

10.4

5.9

3.6

3.7

3.3

2.8

2.8

2.6

2.1

1.3

1.4

1.2

0.8

2.0

0.9

1.1

1.4

Metropolitan status

MSA4 ....................

Non-MSA4 .................

100.1

114.8

72.8

80.4

12.7

12.7

11.1

11.5

2.1

7.4

1.4

3.7

0.7

1.7

0.8

1.5

1

Total consultations include patient encounters in the office, at the hospital, at home, over the telephone, and over the Internet.

2

Estimates include means across all office-based physicians including those who report zero encounters for any of these types.

3

Specialty type is defined in Table VI.

4

MSA is metropolitan statistical area.
Page 20 [ Series 13, No. 164

Table 9. Average number of weekly consultations per physician during last full week of practice with corresponding standard errors, by

type of encounter and physician specialty: United States, 2003–04

Physician specialty1

Total

consultations2

Office

visits

Hospital

visits

Telephone

consultations

Total

consultations2

Office

visits

Hospital

visits

Telephone

consultations

Average number of counsultations reported3 Standard error

All office-based physicians ....... 101.6 73.7 12.7 11.1 2.1 1.3 0.6 0.7

Dermatology ................

Pediatrics ..................

135.7

123.0

124.3

97.2

*1.4

6.4

8.0

15.4

6.4

8.5

6.0

6.6

0.7

0.9

1.9

2.0

General and family practice .......

Internal medicine .............

116.6

113.1

91.4

74.8

6.7

14.1

13.9

16.1

3.4

6.2

2.6

3.2

0.7

1.8

1.3

2.6

Otolaryngology ...............

Obstetrics and gynecology .......

Ophthalmology ...............

Orthopedic surgery ............

Urology ...................

Neurology ..................

Cardiovascular disease .........

105.1

103.9

103.7

100.9

99.0

87.9

84.7

86.8

76.5

98.1

84.9

73.6

58.2

45.4

6.5

10.2

1.9

12.4

12.7

18.6

28.0

10.6

13.9

5.0

6.0

8.9

10.0

10.7

6.1

6.4

7.1

4.7

5.3

5.3

4.4

4.6

3.9

6.2

3.8

3.6

4.1

2.4

0.8

1.2

0.5

1.1

1.3

2.1

2.1

2.0

2.7

0.9

1.1

1.4

1.8

1.7

General surgery ..............

Psychiatry..................

Other specialties..............

65.6

55.1

88.4

40.2

42.2

52.5

21.4

5.3

23.2

3.6

6.3

7.5

3.8

3.8

5.5

2.7

2.4

3.3

2.8

1.1

2.6

0.5

1.1

1.5

* Figure does not meet standard of reliability or precision.

1

Physician specialty is defined in Table V.

2

Total consultations include patient encounters in the office, at the hospital, at home, over the telephone, and over the Internet.

3

Estimates include means across all office-based physicians including those who report zero encounters for any of these types.
Series 13, No. 164 [ Page 21

Appendix I

Technical Notes

Data collection

The NAMCS data collection is

authorized under Section 308d of

the Public Health Service Act

(Title 42 United States Code, Section

306[242k]). Participation is voluntary.

NAMCS utilizes a multistage probability

sample design involving samples of 112

geographic primary sampling units

(PSUs), physicians within PSUs, and

patient visits within physician practices.

PSUs are counties, groups of counties,

county equivalents (such as parishes or

independent cities), or towns and

townships for some PSUs in New

England. For the 2003–04 NAMCS,

6,000 physicians were selected from the

master files of the American Medical

Association (AMA) and American

Osteopathic Association (AOA). Of

these physicians, 3,968 of them were in

scope (eligible to participate in the

survey). Sampled physicians were

screened at the time of the survey using

the Physician Induction Interview (PII)

form before selecting a sample of

patient visits from a randomly selected

week. During the 2003 and 2004 rounds

of the survey, 2,235 physicians

completed the PII and provided visit

encounter data, for an unweighted

physician response rate of 56.3 percent.

The average physician universe for

2003–04, sample size, and unweighted

response rates by physician specialty are

shown in Table I. Physicians not seeing

patients in an office during their

sampled week often did not complete

the practice information requested on

the PII. For this report, they were

considered as nonrespondents, and

sampling weights were adjusted to

account for them.

The scope of NAMCS is visits to

the offices of nonfederally employed

physicians classified by the AMA or

AOA as ‘‘office-based, patient care.’’

Physicians working in private,

nonhospital-based clinics and health

maintenance organizations (HMOs) were

within the scope of the survey.

Physicians in the specialties of

anesthesiology, pathology, and radiology

were excluded. Physicians practicing in

federal and nonfederal hospitals,

including hospital-based outpatient

clinics, and other institutional settings

(for example, nursing homes) were also

excluded.

Among sampled physicians,

66.1 percent were in scope at the time

of the survey and 33.9 percent were out

of scope. As shown in Figure 1, sampled

physicians were out of scope if their

practice was hospital-based; they were

federally employed; in the specialties of

anesthesiology, pathology, or radiology;

or nonoffice-based (institutional,

occupational) (16.0 percent); retired or

deceased (9.5 percent); or nonpracticing

because their job was nonclinical or

they were temporarily not practicing

(e.g., on sabbatical or on military detail)

(4.4 percent). Table II presents the

reasons physicians were out of scope in

more detail. Changes in work status for

sampled physicians could occur because

the time between creating the AMA and

AOA sample and the interview could

range from 3 to 18 months.

Additionally, only one-fourth of the

AMA master file is surveyed each year

to obtain updated information, and

response to this survey is low (32). As a

result, information on the master file

tends to be outdated.

The U.S. Census Bureau, acting as

the data collection agent for the survey,

provided training to field representatives

(FRs) throughout the Nation. These FRs

oversaw data collection at the

physician’s office. They contacted

physicians for induction into the survey

after an advance letter was mailed by

NCHS notifying the physicians of their

Table I. Average number of physicians in the universe, total sample, sample response categories for the Physician Induction Interview, and

unweighted response rate by physician stratum: National Ambulatory Medical Care Survey, 2003–04

2-year sample

Response rate

Physician stratum Universe1 Total Out of scope2 In scope Nonrespondents Respondents (unweighted)3

Total ..................... 486,427 6,000 2,032 3,968 1,733 2,235 56.3

General and family practice ....... 71,354 634 230 404 151 253 62.6

Osteopathy ................. 27,706 460 165 295 135 160 54.2

Internal medicine ............. 74,044 342 118 224 94 130 58.0

Pediatrics .................. 48,863 394 166 228 75 153 67.1

General surgery .............. 20,070 398 145 253 88 165 65.2

Obstetrics and gynecology ....... 33,236 314 95 219 111 108 49.3

Orthopedic surgery ............ 18,389 274 59 215 104 111 51.6

Cardiovascular diseases ......... 17,094 416 104 312 165 147 47.1

Dermatology ................ 8,472 234 49 185 69 116 62.7

Urology ................... 8,691 306 70 236 93 143 60.6

Psychiatry.................. 30,252 562 245 317 149 168 53.0

Neurology .................. 9,386 504 185 319 158 161 50.5

Ophthalmology ............... 16,095 252 59 193 80 113 58.5

Otolaryngology ............... 8,038 294 71 223 91 132 59.2

All other specialties ............ 94,741 616 271 345 170 175 50.7

1

Data were derived from the American Medical Association and the American Osteopathic Association and represent the average number of physicians who were eligible for the 2003 and 2004 NAMCS.

2

See Table II for reasons physicians were out of scope.

3

Response rate is the number of respondents divided by number of in-scope physicians.
Page 22 [ Series 13, No. 164

Table II. Reasons sampled physicians were out of scope for the 2003–04 National

Ambulatory Medical Care Survey

Reason Sample size Percent of physicians

All out-of-scope physicians .......... 2,032 100.0

Works in hospital ED or OPD1

........ 592 29.1

Retired ...................... 521 25.6

Works in institutional setting ......... 139 6.8

Unable to locate ................ 100 4.9

Works in industrial setting .......... 91 4.5

Temporarily not practicing .......... 89 4.4

Federally employed .............. 74 3.6

Not licensed ................... 65 3.2

Sees no ambulatory patients......... 61 3.0

Nonoffice-based practice ........... 54 2.7

Administrator .................. 51 2.5

Deceased .................... 48 2.4

Moved out of United States ......... 41 2.0

Moved out of primary sampling unit .... 14 0.7

Radiologist, anesthesiologist, or

pathologist ................... 11 0.5

Other ineligible ................. 81 4.0

1

ED is emergency department and OPD is outpatient department.

selection in the survey. During the who see patients in office settings and

induction interview, the visit sampling annual office visits are unbiased

rate is established, and the final estimates based on a complex sampling

disposition of the interview is recorded. design with multistage estimation.

The induction interview is also used to Physician weights were used to estimate

obtain basic information about the national numbers and characteristics of

practice such as the physician’s office-based physicians including

employment status, ownership of the characteristics about the physician (e.g.,

practice, practice size, and office type. sex, age, specialty) and the practice

Sample physicians are asked to (e.g., number of physicians in the

complete Patient Record forms (PRFs) practice, single or multispecialty

for a systematic sample of about 30 practice, type and number of patient

visits occurring during a randomly encounters in last full week of practice).

assigned 1-week period. In most cases, The visit weight was used to estimate

physicians or their staff completed the the numerator (annual volume of office

information requested from patient visits) for the rate of annual office visits

medical records. Confidentiality of the per physician (Table 3).

data collected in the survey is protected A distinction should be made

under the Privacy Act, Public Health between estimates of patient volume

Service Act, Title 42 of the United obtained by asking the physician a

States Code, Section 242m (d), and Title question and by counting the number of

V of the E-Government Act of 2002. encounters and weighting them.

The NAMCS protocol with a waiver of Information about encounters from the

patient authorization was approved by last full week of work is based on the

the NCHS Research Ethics Review respondent’s memory rather than on

Board in accordance with the Privacy records (see question 19a in Appendix

Rule of the Health Insurance Portability III). Information about the number of

and Accountability Act (HIPAA) of visits that occur during the randomly

2003. assigned reporting week is based on

counts from records maintained by the

Estimation office. Characteristics about the office

visits such as face-to-face duration are

In this report, estimates are based obtained via medical record abstraction

on two different sampling weights: one on a sample of encounters during the

for nonfederal office-based physicians randomly assigned week.

and one for office visits to these Both the NAMCS physician and

physicians. Estimates of physicians office visit estimation procedures have

three basic components: 1) inflation by

reciprocals of the sampling selection

probabilities, 2) adjustment for physician

nonresponse, and 3) a calibration ratio

adjustment between the number of

physicians in the sample frame between

the time the sample was selected and

the time that the NAMCS data were

collected. For each physician, the

sampling selection probability reflects

the probability of PSU selection and

selection of physicians within each PSU.

The physician nonresponse adjustment

factor is the sample weight for

responding physicians augmented by a

factor accounting for the amount of

nonresponse by similar physicians.

Similar physicians were judged to be

physicians having the same specialty

designation and practicing in the same

PSU, region, or MSA status. The

calibration ratio adjusts the number of

physicians based on the sample frame

within specialty stratum and region cells

to reflect universe counts provided by

AMA and AOA just prior to the

NAMCS weights being finalized. For

example, the 2003 estimated number of

physicians increased from 280,500 to

312,400 after calibration ratios were

applied. Similarly, the 2004 estimated

number of physicians increased from

282,100 to 309,900 after application of

the calibration ratios.

The sample weights for office visits

include the same physician nonresponse

adjustment and calibration ratio

components utilized in the physician

weight. The major difference between

the physician and visit weight is in the

sampling probabilities for visits. That is,

the visit sample selection probabilities

reflect selection of PSUs, selection of

physicians within each PSU, and

selection of visits within physician

practices. In addition, the visit weights

go through a smoothing process so that

excessively large visit weights are

truncated and a ratio adjustment is

performed. This technique preserves the

total estimated visit count within each

specialty by shifting the excess from

visits with the largest weights to visits

with smaller weights. More details on

the NAMCS sampling design and

estimation process have been published

(7,8).
Series 13, No. 164 [ Page 23

To describe the distribution of

hospital encounters (seeing patients in a

hospital setting rather than in the office)

by physician specialty (Figure 8),

arithmetic modifications were made to

the total number of hospital encounters

reportedly made in the last full week of

practice by specialty to approximate an

annual number of hospital encounters.

The underlying assumption is that the

ratio of reported last full week of office

encounters to the annual NAMCS visit

estimates of office visits is the same as

would be found for hospital encounters

if NCHS were to actually sample the

hospital encounters made by officebased physicians during a randomly

assigned week. For example, the ratio of

the weighted volume of office visits for

all physicians (908,440,000) divided by

the weighted number of office visits

during the last full week of practice

(22,509,800) was 40.4. Thus, the

weighted weekly number of hospital

visits (3,526,300 visits) multiplied by

40.4 yielded an estimated 142 million

annual hospital visits. To present this

estimate by physician specialty, these

calculations were performed separately

for each specialty and then summed for

the total number of annual hospital

patient encounters made by office-based

physicians.

Coverage quality

Two internal evaluations of the

NAMCS sampling frame have been

conducted. The completeness of the

AMA frame was evaluated by

comparing physicians from two states

(California and Georgia) from the AMA

sampling frame with the American

Medical Information (AMI) Physician

and Surgeons database. The study found

that the AMI had more current

information on physicians than found on

the AMA frame. However, the AMA

was more complete (33) ( e.g., had more

physicians in the frame who in fact saw

patients in an office-setting).

Complement surveys conducted in the

1997–1999 NAMCS included 500

additional physicians that were not

designated as ‘‘office-based’’ in each

survey year to determine how many

office visits were missed by limiting

the survey to ‘‘office-based’’ physicians.

The study found that 17 percent of

nonoffice-based physicians saw patients

in an office. The majority of these

physicians were hospital-based

physicians who occasionally saw

patients in an office. Visits to

nonoffice-based physicians represent

11 percent of all visits (34). Thus,

NAMCS estimates of physicians who

see patients in an office and the number

of office visits may be slightly underestimated.

Sampling errors

The standard error is primarily a

measure of the sampling variability that

occurs by chance when only a sample,

rather than an entire universe, is

surveyed. The standard error does not

measure any systematic biases in the

data. The standard errors presented in

the tables and used in tests of

significance for this report were

estimated using SUDAAN software.

SUDAAN computes standard errors by

using a first-order Taylor approximation

of the deviation of estimates from their

expected values. A description of the

software and the approach it uses has

been published (9). The relative standard

error (RSE) of an estimate is obtained

by dividing the standard error by the

estimate itself. The result is then

expressed as a percentage of the

estimate.

Nonsampling errors

As in any survey, results are subject

to both sampling and nonsampling

errors. Nonsampling errors include

reporting and processing errors as well

as biases due to nonresponse and

incomplete response. The magnitude of

the nonsampling errors cannot be

computed. However, these errors were

kept to a minimum by procedures built

into the operation of the survey. To

eliminate ambiguities and encourage

uniform reporting, attention was given

to the phrasing of items, terms, and

definitions. Also, pretesting of most data

items and survey procedures was

performed. Quality control procedures,

consistency, and edit checks reduced

errors in data coding and processing.

Coding error rates ranged from 0.1 to

1.1 for various data items.

Adjustments for survey

nonresponse—The weighted response

rate for physicians who provided visit

data for their sampled week in the

2003–04 NAMCS Physician Induction

Interview (PII) form was 56.8 percent.

Table III presents weighted

characteristics of NAMCS respondents

and nonrespondents, along with

weighted response rates. Distributions

were similar, with the exception of

annual visit volume; practices with low

annual visit volume were more likely to

cooperate.

Additionally information on practice

size and ownership was obtained from

two-thirds of survey nonrespondents. A

comparison between respondents and

nonrespondents on these characteristics

found that response was slightly greater

for physicians in large practices

compared with solo and partner

practices. Resulting estimates of

nonresponse bias on items related to

practice size, such as EMR use, were

found to be negligible (i.e., less than

20% of the standard error for the

national estimate) (data not shown).

Adjustments for item nonresponse—

Item nonresponse rates in the NAMCS

PII varied considerably in the survey.

Most nonresponse occurs when the

needed information is unknown or

unavailable to the respondent or the

respondent refuses to answer the item.

Nonresponse can also result when the

information is available, but survey

procedures are not followed and the

item is left blank (i.e., interview did not

follow the correct skip pattern). In this

report, the majority of estimates

presented include a combined entry of

‘‘unknown’’ or ‘‘blank’’ to display

missing data. Estimates based on

categorical responses will generally

include the missing cases in the

denominator. Table IV presents

information on item nonresponse for

variables presented in this report.

Estimates based on numeric entries,

such as volume of encounters during the

last full week of practice, were an

exception to this rule because computed
Page 24 [ Series 13, No. 164

Table III. Characteristics of the 2003–04 National Ambulatory Medical Care Survey, physician respondents and nonrespondents to the

Physician Induction Interview

Physician characteristic1

Number of

sampled

in-scope

physicians2

Total

sample

percent

distribution3

(weighted)

Responding

physician

distribution4

(weighted)

Nonresponding

physician

distribution5

(weighted)

Weighted

response

rate6

All office-based physicians ....... 3,968 100.0 100.0 100.0 0.568

Age

Under 35 years ..............

35–44 years ................

45–54 years ................

55–64 years ................

65 years and over.............

128

1,039

1,429

975

397

4.1

27.6

36.2

23.1

8.9

5.0

28.0

34.3

23.9

8.8

3.0

27.1

38.8

22.1

9.0

0.688

0.576

0.538

0.587

0.564

Sex

Male .....................

Female ...................

740

3,228

21.8

78.2

22.3

77.7

21.1

78.9

0.582

0.564

Region

Northeast ..................

Midwest ...................

South ....................

West .....................

907

888

1,272

901

21.4

22.3

33.7

22.6

20.5

22.9

35.4

21.3

22.6

21.6

31.6

24.2

0.544

0.582

0.595

0.536

Metropolitan status

MSA7 ....................

Not MSA7 .................

3,540

428

88.2

11.8

86.6

13.4

90.2

9.8

0.558

0.642

Physician specialty8

General or family practice ........

Internal medicine .............

Pediatrics ..................

General surgery ..............

Obstetrics and gynecology .......

Orthopedic surgery ............

Cardiovascular diseases .........

Dermatology ................

Urology ...................

Psychiatry..................

Neurology ..................

Opthalmology ...............

Otolaryngology ...............

All other specialties ............

554

243

231

240

234

235

323

188

237

327

320

198

228

410

17.6

15.5

9.0

3.9

7.7

5.0

4.6

2.2

2.2

5.7

2.0

4.0

2.1

18.5

18.9

15.7

10.6

4.4

6.8

4.6

3.7

2.4

2.3

5.5

1.8

4.2

2.1

17.0

15.7

15.3

7.0

3.3

8.9

5.6

5.7

1.9

1.9

6.1

2.3

3.8

2.0

20.4

0.613

0.574

0.665

0.633

0.500

0.516

0.462

0.618

0.614

0.541

0.507

0.593

0.588

0.523

Specialty type8

Primary care................

Surgical ...................

Medical ...................

1,238

1,268

1,462

49.0

23.0

28.1

51.4

22.9

25.7

45.8

23.0

31.2

0.596

0.567

0.520

Practice type9

Solo .....................

Two physicans ...............

Group or HMO10..............

Medical school or government .....

Other.....................

Unclassified.................

1,240

277

1,389

101

65

896

29.4

6.5

34.3

2.3

1.7

25.8

28.3

7.1

34.6

2.6

1.8

25.6

30.9

5.8

33.8

1.9

1.7

26.0

0.547

0.618

0.574

0.646

0.582

0.564

See footnotes at end of table.
Series 13, No. 164 [ Page 25

Table III. Characteristics of the 2003–04 National Ambulatory Medical Care Survey, physician respondents and nonrespondents to the

Physician Induction Interview—Con.

Physician characteristic1

Number of

sampled

in-scope

physicians2

Total

sample

percent

distribution3

(weighted)

Responding

physician

distribution4

(weighted)

Nonresponding

physician

distribution5

(weighted)

Weighted

response

rate6

Annual visit volume9,11

Low......................

Medium ...................

High .....................

1,334

1,327

1,307

32.2

33.2

34.6

34.2

30.5

35.3

29.6

36.7

33.7

0.603

0.522

0.580

1

Characteristic information is from the master files of the American Medical Association and the American Osteopathic Association.

2

In-scope physicians are those who verified that they were nonfederal and involved in direct patient care in an office-based setting, excluding the specialties of radiology, pathology, and

anesthesiology.

3

Total physicians are those who were selected from the master files of the American Medical Association and the American Osteopathic Association.

4

Responding physicians are those who were in scope and responded to the NAMCS Physician Induction Interview (PII) form.

5

Nonresponding physicians are those who were in scope and refused to respond to the NAMCS PII form.

6

Numerator is the number of in-scope physicians who responded to the NAMCS PII form. Denominator is all in-scope sampled physicians.

7

MSA is metropolitan statistical area.

8

Physician specialty and specialty type is defined in ‘‘Physician specialty groups’’ section of ‘‘Technical Notes.’’

9

Chi-square test of association is significant at p < 0.05.

10HMO is health maintenance organization.

11Low is the lowest third of annual visit volume, medium is the middle third, and high is the highest third.

estimates exclude cases with missing

data. If nonresponse is random, the

observed distribution for the reported

item (i.e., excluding cases for which the

information is unknown) would be close

to the true distribution. However, if with high levels of missing responses.

nonresponse is not random, the observed For items with a nonresponse greater

distribution could vary significantly than 50 percent, data are not presented.

from the actual distribution. Researchers

need to decide how best to treat items Tests of significance and

rounding

Table IV. Weighted item nonresponse rates for report variables

In this report, the determination of

Weighted item statistical inference is based on a Variable nonresponse

two-tailed t-test. The Bonferroni

Race and ethnicity ...........................

Graduate of foreign medical school.................

Practice-based research network .................

Electronic medical record.......................

Computerized prescription order entry (CPOE) .........

Percent of prescriptions written using CPOE ...........

Electronic billing records .......................

Number of managed care contracts ................

Percent revenue from managed care contracts .........

Percent revenue from private insurance ..............

Percent revenue from Medicare...................

Percent revenue from Medicaid ...................

Percent revenue from other sources ................

Any new patients ............................

New self-pay patients accepted ...................

New Medicare patients accepted ..................

New noncapitated private insurance patients accepted ....

New Medicaid patients accepted ..................

New Worker’s compensation patients accepted .........

New capitated private insurance patients accepted ......

New no charge or charity patients accepted ...........

Difficulty referring Medicaid patients ................

Difficulty referring Medicare patients ................

Difficulty referring private insurance patients ...........

Difficulty referring uninsured patients................

Volume of office visits during last full week of practice .....

Weekly hospital visits .........................

Weekly telephone consultations ...................

Weekly home visits ..........................

Weekly e-mail or Internet consultations ..............

Hours of EMTALA-mandated care per week1 ..........

29.0 inequality was used to establish the

5.7 critical value for statistically significant 12.1 differences (0.05 level of significance) 1.1

1.8 based on the number of possible

9.1 comparisons within a particular variable

8.1 (or combination of variables) of interest.

3.9 Terms relating to differences such as 20.9

8.0 ‘‘greater than’’ or ‘‘less than’’ indicate

7.4 that the difference is statistically

8.7 significant. A lack of comment

16.1 regarding the difference between any 0.7

3.0 two estimates does not mean that the

3.2 difference was tested and found to be

9.9 not significant. 4.1

6.5 A weighted least-squares regression

10.5 analysis was used to determine the

12.0 significance of trends by age. For the

21.1 weighted least-squares test, the null 19.8

13.4 hypothesis is that the slope, β, of the

22.1 regression line between the two

1.8 variables of interest does not

10.8 significantly differ from zero, and the 12.4

10.1 alternative hypothesis is that it does

12.7 differ from zero (i.e., H0 : β = 0, and HA 14.1 : β 7 0). In this modified least-square

1

EMTALA is the Emergency Medical Treatment and Labor Act of 1986. regression, each estimate is weighted by

the inverse of the standard error (35).
Published and flagged estimates

Estimates are not presented unless a

reasonable assumption regarding their

probability distributions is possible on

the basis of the Central Limit Theorem.

This theorem states that given a

sufficiently large sample size, the

sample estimate approximates the

population estimate and, upon repeated

sampling, its distribution would be

approximately normal.

In this report, estimates are not

presented if they are based on fewer

than 20 cases in the sample data; only

an asterisk (*) appears in the tables.

Estimates based on 20–29 cases are

presented with asterisks regardless of

the RSE level. Estimates based on 30 or

more cases include an asterisk only if

the RSE of the estimate exceeds

30 percent.

In the tables, estimates of

office-based physicians have been

rounded to the nearest hundred.

Consequently, estimates will not always

add to totals. Rates and percentages

were calculated from original unrounded

figures and do not necessarily agree

with figures calculated from rounded

data.

Physician specialty groups

In this report, physician specialty is

defined in two ways: ‘‘physician

specialty’’ and ‘‘specialty type.’’

Physician specialty is based on the 15

strata of physician specialties used for

sampling purposes in the NAMCS

survey design. One stratum, doctors of

osteopathy, was based on information

from the AOA. The ‘‘physician

specialty’’ classification presented in this

report include the same physician

specialty strata used for sampling

purposes with the exception of the

doctors of osteopathy stratum, which is

combined with doctors of medicine in

the following 14 categories: general and

family practice, internal medicine,

pediatrics, general surgery, obstetrics

and gynecology, orthopedic surgery,

cardiovascular diseases, dermatology,

urology, psychiatry, neurology,

ophthalmology, otolaryngology, and a

residual category of other specialties.

Table V defines the 14 ‘‘physician

Table V. Reclassification of physician specialty based on American Medical Association

subspecialty designations for use in the National Ambulatory Medical Care Survey

Physician specialty Subspecialty designation

General practice . . . . . . . . . . . . . . FP - Family practice

FPG - Family practice, geriatric medicine

FSM - Sports medicine (family practice)

GP - General practice

Internal medicine . . . . . . . . . . . . . IM - Internal medicine

Pediatrics . . . . . . . . . . . . . . . . . . ADL - Adolescent medicine

CCP - Critical care pediatrics

DBP - Developmental-behavioral pediatrics

MPD - Internal medicine (pediatrics)

NDN - Neurodevelopmental disabilities

NPM - Neonatal-perinatal medicine

PD - Pediatrics

PDA - Pediatric allergy

PDC - Pediatric cardiology

PDE - Pediatric endocrinology

PDI– Pediatric infectious diseases

PDP - Pediatric pulmonology

PDT - Medical toxicology (pediatrics)

PEM - Pediatric emergency medicine

PG - Pediatric gastroenterology

PHO - Pediatric hematology or oncology

PN - Pediatric nephrology

PPR - Pediatric rheumatology

PSM - Sports medicine (pediatrics)

General surgery . . . . . . . . . . . . . . GS - General surgery

Obstetrics and gynecology . . . . . . . GO - Gynecological oncology

GYN - Gynecology

MFM - Maternal and fetal medicine

OBG - Obstetrics and gynecology

OBS - Obstetrics

OCC -Critical care medicine (obstetrics and gynecology)

REN - Reproductive endocrinology

Orthopedic surgery . . . . . . . . . . . . OAR - Adult reconstructive orthopedics

OFA - Foot and ankle orthopedics

OMO - Musculoskeletal oncology

OP - Pediatric orthopedics

ORS - Orthopedic surgery

OSM - Sports medicine (orthopedic surgery)

OSS - Orthopedic surgery of the spine

OTR - Orthopedic trauma

Cardiovascular diseases . . . . . . . . . CD - Cardiovascular diseases

Dermatology . . . . . . . . . . . . . . . . D - Dermatology

Urology . . . . . . . . . . . . . . . . . . . U - Urology

UP - Pediatric urology

Psychiatry. . . . . . . . . . . . . . . . . . ADP - Addiction psychiatry

CHP - Child psychiatry

NUP - Neuropsychiatry

P - Psychiatry

PFP - Forensic psychiatry

PYA - Psychoanalysis

PYG - Geriatric psychiatry

Neurology . . . . . . . . . . . . . . . . . . CHN - Child neurology

CN - Clinical neurophysiology

ESN - Endovascular surgical neuroradiology

N - Neurology

NRN - Neurology (diagnostic radiology)

Ophthalmology . . . . . . . . . . . . . . . OPH - Ophthalmology

PO - Pediatric ophthalmology

Otolaryngology . . . . . . . . . . . . . . . NO - Otology-neurotology

OTO - Otolaryngology

PDO - Pediatric otolaryngology

Page 26 [ Series 13, No. 164
Series 13, No. 164 [ Page 27

Table V. Reclassification of physician specialty based on American Medical Association specialty’’ categories in terms of

subspecialty designations for use in the National Ambulatory Medical Care Survey—Con. self-designated subspecialty provided by

Physician specialty Subspecialty designation

All other ................... A - Allergy

ADM - Addiction medicine

AI - Allergy and immunology

ALI - Allergy and immunology or diagnostic laboratory immunology

AM - Aerospace medicine

AMI - Adolescent medicine (internal medicine)

AS - Abdominal surgery

CBG - Clinical biochemical genetics

CCG - Clinical cytogenetics

CCM - Critical care medicine

CCS - Critical care surgery

CFS - Craniofacial surgery

CG - Clinical genetics

CMG - Clinical molecular genetics

CRS - Colon and rectal surgery

CS - Cosmetic surgery

DDL - Dermatological immunology or

diagnostic laboratory immunology

DIA - Diabetes

DS - Dermatologic surgery

EM - Emergency medicine

END - Endocrinology

EP - Epidemiology

ESM - Sports medicine (emergency medicine)

ETX - Medical toxicology (emergency medicine)

FPS - Facial plastic surgery

GE - Gastroenterology

GPM - General preventive medicine

HEM - Hematology

HEP - Hepatology

HNS - Head and neck surgery

HO - Hematology or oncology

HS - Hand surgery

HSP - Hand surgery (plastic surgery)

HSS - Hand surgery (surgery)

IC - Interventional cardiology

ICE - Cardiac electrophysiology

ID - Infectious diseases

IG - Immunology

ILI - Internal medicine or diagnostic laboratory immunology

IMG - Geriatric medicine (internal medicine)

ISM - Sports medicine (internal medicine)

LM - Legal medicine

MDM - Medical management

MG - Medical genetics

NEP - Nephrology

NS - Neurological surgery

NSP - Pediatric surgery (neurology)

NTR - Nutrition

OM - Occupational medicine

OMF - Oral and maxillofacial surgery

OMM - Osteopathic manipulative medicine

ON - Medical oncology

PA - Clinical pharmacology

PCC - Pulmonary critical care medicine

PCS - Pediatric cardiothoracic surgery

PDS - Pediatric surgery

PE - Pediatric emergency medicine (emergency medicine)

PHM - Pharmaceutical medicine

PHP - Public health or general preventive medicine

PLI - Pediatric diagnostic laboratory immunology

PLM - Palliative medicine

PM - Physical medicine and rehabilitation

PMD - Pain medicine

PMM - Sports medicine (physical medicine and rehabilitation)

PRM - Pediatric rehabilitation medicine

the AMA. The ‘‘physician specialty’’

classification is updated with

information provided by sampled

physicians at the time of the survey. In

this classification, for example, a

pediatric cardiologist is grouped with

other pediatricians.

The second ‘‘specialty type’’

classification divides AMA selfdesignated subspecialties into three

major categories: primary care, surgical

specialties, and medical specialties

(Table VI) and puts more emphasis on

specialization type. For example,

pediatric cardiologist is classified as a

medical specialty in this classification.

It should be noted that although

emergency medicine physicians made up

2.5 percent of sampled physicians in

2003–04 and are included in the

physician specialty category ‘‘all other

specialties,’’ few of these physicians are

included in NAMCS because they rarely

see patients in an office setting and thus

are often outside the scope of the

survey.

Population figures and rate

calculation

The denominators used in

calculating 2003–04 physician-topopulation rates by geographic region

are census 2000-based postcensal

estimates of the civilian noninstitutional

population of the United States. The

population estimates are special

tabulations developed by the Population

Division, U.S. Census Bureau from the

July 1, 2003, and July 1, 2004, sets of

state population estimates by region.

Population estimates by MSA status are

based on data from the 2003–04

National Health Interview Survey

(NHIS), National Center for Health

Statistics (NCHS), adjusted to U.S.

Census Bureau definition of core-based

statistical areas as of December 2003

and December 2004. See http://

www.census.gov/population/www/

estimates/metrodef.html for more about

MSA definitions.

Estimates of visit rates for MSAs

and non-MSAs in 2003–04 may differ

somewhat from those reported in 2002

and previous years because of

methodological differences in how the
Page 28 [ Series 13, No. 164

Table V. Reclassification of physician specialty based on American Medical Association

subspecialty designations for use in the National Ambulatory Medical Care Survey—Con.

Physician specialty Subspecialty designation

All other—Con ............... PRO - Proctology

PS - Plastic surgery

PSH - Plastic surgery within the head and neck

PTX - Medical toxicology (preventive medicine)

PUD - Pulmonary diseases

RHU - Rheumatology

SCI - Spinal cord injury

SM - Sleep medicine

SO - Surgical oncology

TRS - Traumatic surgery

TS - Thoracic surgery

TTS - Transplant surgery

UCM - Urgent care medicine

UM - Undersea medicine

VM - Vascular medicine

VS - Vascular surgery

OS - Other specialty

US - Unspecified

Table VI. Reclassification of physician specialty into specialty type for use in the National Ambulatory Medical Care Survey

Specialty type Physician subspecialty

Primary care specialties ......... Family practice, geriatric medicine (family practice), sports medicine (family practice), general practice, internal medicine, internal

medicine (pediatrics), adolescent medicine (internal medicine), geriatric medicine (internal medicine), adolescent medicine,

pediatrics, pediatric sports medicine, gynecology, maternal and fetal medicine, obstetrics and gynecology, obstetrics

Surgical specialties ............ General surgery, gynecological oncology, critical care medicine (obstetrics and gynecology), hand surgery (orthopedic surgery),

adult reconstructive orthopedics, foot and ankle orthopedics, musculoskeletal oncology, pediatric orthopedics, orthopedic surgery,

sports medicine (orthopedic surgery), orthopedic surgery of the spine, orthopedic trauma, urology, pediatric urology,

ophthalmology, pediatric ophthalmology, otology-neurotology, otology, otolaryngology, pediatric otolaryngology, abdominal surgery,

cardiovascular surgery, colon and rectal surgery, cardiothoracic surgery, craniofacial surgery, critical care surgery, dermatologic

surgery, facial plastic surgery, head and neck surgery, hand surgery (plastic surgery), hand surgery (surgery), critical care

(neurological surgery), neurological surgery, pediatric surgery (neurology), pediatric cardiothoracic surgery, pediatric surgery,

plastic surgery, surgical oncology thoracic surgery, transplant surgery, traumatic surgery, vascular surgery, proctology

Medical specialties ............ Critical care pediatrics, developmental-behavioral pediatrics, neurodevelopmental disabilities, neonatal-perinatal medicine,

pediatric allergy, pediatric cardiology, pediatric endocrinology, pediatric infectious diseases, pediatric pulmonology, medical

toxicology (pediatrics), pediatric emergency medicine, pediatric gastroenterology, pediatric hematology/oncology, pediatric

nephrology, pediatric rehabilitation medicine, pediatric rheumatology, reproductive endocrinology, cardiovascular diseases,

dermatology, psychiatry, addiction psychiatry, child psychiatry, forensic psychiatry, psychoanalysis, geriatric psychiatry, neurology,

child neurology, clinical neurophysiology, neurology (diagnostic radiology), addiction medicine, aerospace medicine, allergy,

allergy and immunology/diagnostic laboratory immunology, cardiac electrophysiology, clinical genetics, clinical biochemical

genetics, clinical cytogenetics, clinical molecular genetics, critical care medicine, dermatological immunology/diagnostic laboratory

immunology, diabetes, emergency medicine, epidemiology, endocrinology, gastroenterology, general preventive medicine,

hematology, hepatology, hematology/oncology, infectious diseases, internal medicine/diagnostic laboratory immunology,

interventional cardiology, legal medicine, medical management, medical genetics, medical toxicology (emergency medicine),

medical toxicology (preventive medicine), medical oncology, nephrology, nutrition, occupational medicine, osteopathic

manipulative medicine, pain medicine, palliative medicine, pediatric emergency medicine (emergency medicine), pediatric/

diagnostic laboratory immunology, pharmaceutical medicine, public health, public health and general preventive medicine, clinical

pharmacology, physical medicine and rehabilitation, pulmonary critical care medicine, pulmonary diseases, sports medicine

(emergency medicine), sports medicine (physical medicine and rehabilitation), rheumatology, spinal cord injury, sleep medicine,

undersea medicine, vascular medicine

denominators were calculated. In survey

years 1992–2002, NHIS used a 1992

definition of MSAs and non-MSAs.

NHIS also used 1990-based census

estimates as controls for calculating

population estimates through 2002.

Because NAMCS used 2000-based

estimates beginning in 2001,

adjustments needed to be made to the

MSA figures obtained from NHIS in

2001 and 2002. For 2003–04, special

tabulations were obtained from the

Office of Analysis and Epidemiology,

NCHS, where 2003 and 2004 NHIS data

were matched to the December 2003

and December 2004 U.S. Census Bureau

definition of core-based statistical areas.

The estimates were further adjusted

based on the 2003–04 population

estimates obtained from the Census

Bureau.
Series 13, No. 164 [ Page 29

Appendix plan. When a physician contracts with a II managed care plan, the plan may pay

the physician at a negotiated rate per

capita, a flat retainer, or on a negotiated Definition of terms fee-for-service basis for patients covered

Geographic region—The 50 states by the plan. Under the contract, the

and the District of Columbia are physician may also serve as the primary

grouped for statistical purposes by the care physician (PCP) for patients under

U.S. Census Bureau into the following the plan. The PCP oversees care for

four geographic regions: these patients as well as provides

referrals to specialists when needed.

Region States included Metropolitan status—Providers are

classified by their location in a

Northeast Connecticut, Maine, metropolitan statistical area or

Massachusetts, New nonmetropolitan statistical area as

Hampshire, New Jersey, follows:

New York, Pennsylvania,

Rhode Island, Vermont + Metropolitan statistical area

(MSA)—As defined by the U.S.

Midwest Illinois, Indiana, Iowa, Office of Management and Budget,

Kansas, Michigan, the definition of an individual MSA

Minnesota, Missouri, involves two considerations: first, a

Nebraska, North Dakota, city or cities of specified population

Ohio, South Dakota, that constitute the central city and

Wisconsin identify the county in which it is

South Alabama, Arkansas, located as the central county;

Delaware, District of second, economic and social

Columbia, Florida, Georgia, relationships with ‘‘contiguous’’

Kentucky, Louisiana, counties that are metropolitan in

Maryland, Mississippi, North character so that the periphery of the

Carolina, Oklahoma, South specific metropolitan area may be

Carolina, Tennessee, Texas,

determined. MSAs may cross state

Virginia, West Virginia lines. In New England, MSAs

consist of cities and towns rather

West Arizona, California, than counties.

Colorado, Idaho, Montana, + Non-MSA—Non-MSA areas are

Nevada, New Mexico, those not defined as MSAs,

Oregon, Utah, Washington, including rural and micropolitan

Wyoming, Alaska, Hawaii areas.

In-scope physician—An in-scope Office—An office is the space

physician is a duly licensed doctor of identified by physicians as a location for

medicine (M.D.) or doctor of osteopathy their ambulatory practice. Offices

(D.O.) who is currently in office-based customarily include consultation,

practice and who spends some time examination, or treatment spaces that

caring for ambulatory patients. Excluded patients associate with the particular

from NAMCS are physicians who are physician.

hospital-based; who specialize in Patient—A patient is an individual

anesthesiology, pathology, or radiology; seeking personal health care services

who are federally employed; who treat and who is not currently admitted to any

only institutionalized patients; or who health care institution on the premises.

are employed full time by an institution Practice size—Practice size was

and spend no time seeing ambulatory defined by the number of physicians in

patients. the practice. Physicians could report a

Managed care contracts—Managed maximum of four locations where they

care includes any type of group health saw patients. For this report, practice

plan using financial incentives or size was usually the number of

specific controls to encourage utilization physicians at the first listed location (see

of specific providers associated with the question 17b. in Appendix III). Practice

size may be underestimated for

physicians working in large practices

with multiple sites.

Primary care specialist—A primary

care specialist has designated a primary

care specialty of general or family

practice, internal medicine, pediatrics,

etc. Primary care specialists are grouped

and presented in Table V. The terms

‘‘primary care specialties’’ and ‘‘primary

care specialists’’ are used

interchangeably throughout this report

and refer to the self-designated

classification by physicians in the AMA

and AOA masterfiles.

Patient payment source—Payment

sources used by patients to pay for

charges incurred during visits are

categorized as follows:

+ Self-pay—Charges billed directly to

the patient that will not be

reimbursed by a third party. Does

not include prepaid plans for which

a copayment is charged.

+ Medicare—Charges paid in part or

in full by a Medicare plan, including

payments made directly to the

physician as well as payments to the

patient.

+ Medicaid/SCHIP—Charges paid in

part or in full by a Medicaid or

State Children’s Health Insurance

Plan (SCHIP), including payments

made directly to the physician as

well as payments to the patient.

SCHIP, enacted as part of the

Balanced Budget Act of 1997, gave

states the opportunity to provide free

or low-cost insurance coverage to

low-income children not otherwise

eligible to be covered by Medicaid.

States began enrolling children in

1998 using Medicaid, state-specific

programs separate from Medicaid, or

both. By 2000, all states had

implemented their SCHIP programs.

+ Private insurance—Charges paid in

part or in full by a private insurance

company, health maintenance

organization (HMO), or other

prepayment plan This includes

independent practice associations

(IPAs) and preferred provider

organizations (PPOs).

+ No charge or charity—Visits for

which no fee is charged (not

including visits paid for as part of a
Page 30 [ Series 13, No. 164

total care package (e.g.,

postoperative visits included in a

surgical fee, pregnancy visits for

which a flat fee was charged, and

HMO and prepaid systems).

+ Other sources—All other sources of

payment not in the preceding

categories. Charges paid under any

other local, state, or federal health

care program such as worker’s

compensation programs and

CHAMPUS.

+ Unknown—Cases where none of the

previous sources of payment

categories was checked.

Three questions on the PII refer to

payment sources used by patients to pay

for charges incurred during a visit: 1)

whether physicians accept new patients

into their practices with selected types

of payment, 2) difficulty in referring

patients with selected types of health

insurance for specialty consultation, and

3) percent of revenues from specific

types of payment. See ‘‘Patient Payment

Source’’ for defininitions.
Series 13, No. 164

[ Page 31

Appendix III

Excerpts from the 2004

Physician

Induction

Interview

form
Page 32 [ Series 13, No. 164
Series 13, No. 164 [ Page 33
Page 34 [ Series 13, No. 164
Vital and Health Statistics

series descriptions

SERIES 1. Programs and Collection Procedures—These reports

describe the data collection programs of the National Center

for Health Statistics. They include descriptions of the methods

used to collect and process the data, definitions, and other

material necessary for understanding the data.

SERIES 2. Data Evaluation and Methods Research—These reports

are studies of new statistical methods and include analytical

techniques, objective evaluations of reliability of collected

data, and contributions to statistical theory. These studies

also include experimental tests of new survey methods and

comparisons of U.S. methodology with those of other

countries.

SERIES 3. Analytical and Epidemiological Studies—These reports

present analytical or interpretive studies based on vital and

health statistics. These reports carry the analyses further than

the expository types of reports in the other series.

SERIES 4. Documents and Committee Reports—These are 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 5. International Vital and Health Statistics Reports—These

reports are analytical or descriptive reports that compare U.S.

vital and health statistics with those of other countries or

present other international data of relevance to the health

statistics system of the United States.

SERIES 6. Cognition and Survey Measurement—These reports are

from the National Laboratory for Collaborative Research in

Cognition and Survey Measurement. They use methods of

cognitive science to design, evaluate, and test survey

instruments.

SERIES 10. Data From the National Health Interview Survey—These

reports contain statistics on illness; unintentional injuries;

disability; use of hospital, medical, and other health services;

and a wide range of special current health topics covering

many aspects of health behaviors, health status, and health

care utilization. They are based on data collected in a

continuing national household interview survey.

SERIES 11. Data From the National Health Examination Survey, the

National Health and Nutrition Examination Surveys, and

the Hispanic Health and Nutrition Examination Survey—

Data from direct examination, testing, and measurement on

representative samples of the civilian noninstitutionalized

population provide the basis for (1) medically defined total

prevalence of specific diseases or conditions in the United

States and the distributions of the population with respect to

physical, physiological, and psychological characteristics, and

(2) analyses of trends and relationships among various

measurements and between survey periods.

SERIES 12. Data From the Institutionalized Population Surveys—

Discontinued in 1975. Reports from these surveys are

included in Series 13.

SERIES 13. Data From the National Health Care Survey—These

reports contain statistics on health resources and the public’s

use of health care resources including ambulatory, hospital,

and long-term care services based on data collected directly

from health care providers and provider records.

SERIES 14. Data on Health Resources: Manpower and Facilities—

Discontinued in 1990. Reports on the numbers, geographic

distribution, and characteristics of health resources are now

included in Series 13.

SERIES 15. Data From Special Surveys—These reports contain

statistics on health and health-related topics collected in

special surveys that are not part of the continuing data

systems of the National Center for Health Statistics.

SERIES 16. Compilations of Advance Data From Vital and Health

Statistics—Advance Data Reports provide early release of

information from the National Center for Health Statistics’

health and demographic surveys. They are compiled in the

order in which they are published. Some of these releases

may be followed by detailed reports in Series 10–13.

SERIES 20. Data on Mortality—These reports contain statistics on

mortality that are not included in regular, annual, or monthly

reports. Special analyses by cause of death, age, other

demographic variables, and geographic and trend analyses

are included.

SERIES 21. Data on Natality, Marriage, and Divorce—These reports

contain statistics on natality, marriage, and divorce that are

not included in regular, annual, or monthly reports. Special

analyses by health and demographic variables and

geographic and trend analyses are included.

SERIES 22. Data From the National Mortality and Natality Surveys—

Discontinued in 1975. Reports from these sample surveys,

based on vital records, are now published in Series 20 or 21.

SERIES 23. Data From the National Survey of Family Growth—These

reports contain statistics on factors that affect birth rates,

including contraception, infertility, cohabitation, marriage,

divorce, and remarriage; adoption; use of medical care for

family planning and infertility; and related maternal and infant

health topics. These statistics are based on national surveys

of women of childbearing age.

SERIES 24. Compilations of Data on Natality, Mortality, Marriage, and

Divorce—These include advance reports of births, deaths,

marriages, and divorces based on final data from the National

Vital Statistics System that were published as National Vital

Statistics Reports (NVSR), formerly Monthly Vital Statistics

Report. These reports provide highlights and summaries of

detailed data subsequently published in Vital Statistics of the

United States. Other special reports published here provide

selected findings based on final data from the National Vital

Statistics System and may be followed by detailed reports in

Series 20 or 21.

For answers to questions about this report or for a list of reports published

in these series, contact:

Information Dissemination Staff

National Center for Health Statistics

Centers for Disease Control and Prevention

3311 Toledo Road, Room 5412

Hyattsville, MD 20782

1-866-441-6247

E-mail: nchsquery@cdc.gov

Internet: www.cdc.gov/nchs
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DHHS Publication No. (PHS) 2007-1735, Series 13, No. 164