NCHS Data Brief ■ No. 47 ■ October 2010

u.s. department of health and human services

Centers for Disease Control and Prevention

National Center for Health Statistics

Visits to Primary Care Delivery Sites: United States, 2008

Esther Hing, M.P.H., and Sayeedha Uddin, M.D., M.P.H.

Key findings 

•	 In 2008, the majority 

of visits to primary care 

delivery sites (84%) occurred 

in physician offices, 11%

in hospital outpatient 

departments (OPDs), 

and 5% in community 

health centers (CHCs).

•	 Patients with Medicaid, 

State Children’s Health 

Insurance Plan (SCHIP) or 

no insurance accounted for a 

higher percentage of visits to 

CHCs (56%) and OPDs 

(40%) than to physician 

offices (17%).

•	 CHCs had a higher ageadjusted percentage of visits 

by patients with one or more 

chronic conditions (56%) 

compared with visits 

physician offices (49%)

and OPDs (49%).

Interest in access, utilization, and quality of primary care has increased due to 

its potential to prevent more serious health-related events (1–4). This report

compares care delivered in physician offices, hospital outpatient departments

(OPDs) and community health centers (CHCs). 

billion ambulatory care visits were made to primary care delivery sites 

(5–7). Although primary care may be provided by any specialty, our analysis

is limited to visits to office-based physicians, CHC providers, and OPD

clinics specializing in internal medicine, family or general practice, general 

pediatrics, and general obstetrics and gynecology.

Keywords: physician offices • hospital outpatient departments • community 

health centers

CHCs and OPDs are important sources of primary care for 

poor populations.

NOTE: Ambulatory setting was significantly associated with poverty level (χ2=4.69, df=4, and p<0.001) . Poverty level estimates 

exclude 4.8% of visits missing patient ZIP Code.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, and National Hospital Ambulatory Medical Care Survey.

Figure 1. Percent distribution of visits to primary care sites, by setting and poverty level in

patient’s ZIP Code: United States, 2008

Under 20% poverty

20–29% poverty

Physician offices Community health centers Outpatient departments

30% or more poverty

All visits

84% 86%

72% 67%

10%

4%

11% 5%

18% 25%

8%

10%
NCHS Data Brief ■ No. 47 ■ October 2010

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•	 Based on the National Ambulatory Medical Care Survey and the National Hospital

Ambulatory Medical Care Survey, there were 664.0 million visits to primary care clinicians

in 2008; 84% were to office-based physicians (556.6 million visits), 11% to hospital OPDs

(73.1 million visits), and 5% were to CHCs (34.3 million visits).

•	 The proportion of visits made to CHCs and OPD clinics combined increased to

approximately one-third of visits, as the poverty level of patients’ neighborhood increased

to 30% or more in poverty (Figure 1).

Visit rates were higher for persons with public insurance.

•	 Private insurance was used more frequently for physician office visits (61%) than for visits

to CHCs (17%) and OPDs (37%). A higher percentage of visits to CHCs (56%) and OPDs

(40%) than to physician offices (17%) were made by patients using only Medicaid, State

Children’s Health Insurance Plan (SCHIP) or no insurance for payment (Figure 2).

Medicaid or SCHIP1 No insurance1 Other Me 1 dicare Pr 2 ivate insurance1

1

Difference between physician office percentage and other settings is statistically significant.

2

Includes patients dually eligible for Medicare and Medicaid.

NOTE: Payment source is the primary expected source of payment.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, and National Hospital Ambulatory Medical Care Survey.

Figure 2. Visits by primary care setting and payment source: United States, 2008

P Medicare Medicaid unins other

Outpatient departments

9%

9%

31%

14%

37%

Private ins Medicare Medicaid No insurance o insPriv insOther

Community health centers

15% 17%

12%

44%

12%

Private insurance/1 sur Medicare Medic /2 Medicaid or SCHIP/1 or No insurance/1 u anceOther/1

Physician offices

5%

13%

17% 61%

4%

•	 Overall, the visit rates for persons with Medicare and persons relying only on Medicaid or 

SCHIP exceeded that for all other payment sources (Figure 3).
NCHS Data Brief ■ No. 47 ■ October 2010

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NOTES: Medicare includes patients eligible for Medicare and Medicaid. SCHIP is State Children’s Health Insurance Plan. 

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, and National Hospital Ambulatory Medical Care Survey.

Figure 3. Visit rates to primary care sites, by primary expected payment source and setting: United States, 2008

Visits per 100 persons

0 100 200 300 400

No insurance

Only Medicaid or SCHIP

Medicare

Private insurance

Hospital outpatient

department

Community health

center

Physician offices

All visits to primary

care sites

195

250

312

78

178

219

205

54

3

9

43

9

14

22

65

15

The chronic disease burden is higher in CHCs than in other settings.

•	 After adjusting for differences in age distributions across settings, CHCs had a higher

percentage of visits by patients with one or more chronic conditions (56%) compared with 

physician offices (49%) and OPDs (49%) (Figure 4).

1

Community health center (CHC) percentage differs significantly from percentages in other settings. 

2

CHC percentage differs significantly from physician office percentage. 3

Physician office percentage differs significantly from outpatient department (OPD) percentage.

NOTES: CHC and OPD percentages were age adjusted to physician office distribution. In physician offices, the percentage of visits by patients aged 65 

years and over was higher and the percentage of visits by patients aged 18–44 years was lower than comparable percentages in OPDs and CHCs. All 

visits with any chronic condition includes conditions shown as well as: cancer, cerebrovascular disease, congestive heart failure, chronic renal failure, 

chronic obstructive pulmonary disease, ischemic heart disease, obesity, and osteoporosis.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey, and National Hospital Ambulatory Medical Care Survey.

Figure 4. Visits with selected chronic conditions, by primary care setting: United States, 2008 

0 10 20 30 40 50 60

Outpatient departments

Community health centers

Physician offices

Asthma2

Arthritis

Depression1

Diabetes1

Hyperlipidemia3

Hypertension2

All visits with any

chronic condition1

49

49

56

24

26

30

17

12

16

11

12

15

8

9

12

10

9

13

6

8

8

Age-adjusted percent of visits
NCHS Data Brief ■ No. 47 ■ October 2010

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•	 The age-adjusted percentage of CHC visits made by patients with diabetes (15%) and

depression (12%) exceeded analogous percentages in physician offices and hospital OPDs.

The age-adjusted percentage of CHC visits made by patients with hypertension (30%)

exceeded the percentage in physician offices (24%), while the age-adjusted percentage of

physician office visits by patients with hyperlipidemia (17%) exceeded the percentage in

OPDs (12%).

•	 The age-adjusted percentage of visits for acute conditions in CHCs (39%) was lower

compared with OPDs (46%). The comparable percentage for office-based physicians (40%)

was similar to that for CHCs (data not shown).

Imaging and nonmedication treatment were more common at OPDs.

•	 Hospital OPDs had a higher age-adjusted percentage of visits during which imaging was 

ordered or provided (18%) compared with physician offices (14%) and CHCs (11%) (Table).

Table. Selected services ordered or provided by primary care setting: United States, 2008

Services ordered or provided Physician offices Community health centers Outpatient departments

Age-adjusted percentage of visits

Drug or immunization 

mentioned

80 83 81

Lab and other tests1 50 49 52

Health education service2 39 40 46

Any imaging3 14 11 18

Nonmedication treatment3,4 10 10 16

1

Lab and other tests include scope procedures, biopsy. EKG/ECG, spirometry/pulmonary function test, and other services. 2

Health education services include education about asthma, diet and nutrition, exercise, growth and development, injury prevention, stress management, tobacco 

use and exposure, weight reduction, and other education.

3

Difference between outpatient department and other settings is statistically significant. 4

Non-medication treatment includes: complementary and alternative medicine, durable medical equipment, home health care, hospice care, physical therapy, 

radiation therapy, speech and occupational therapy, psychotherapy, other mental health counseling, excision of tissue, orthopedic care, wound care, other 

nonsurgical procedures, and other surgical procedures.

NOTES: Community health center (CHC) and outpatient department (OPD) visits were age-adjusted to physician office distribution. In physician offices, the

percentage of visits by patients 65 years and older was higher and the percentage of visits by patients aged 18–44 years was lower than comparable percentages

in CHCs and OPDs.

SOURCES: CDC/NCHS, National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey.

•	 Hospital OPDs also had a higher percentage of age-adjusted visits during which 

nonmedication treatment was ordered or provided (16%) compared with physician offices

(10%) and CHCs (10%).

•	 There was no difference among settings in the age-adjusted percentage of visits in which

drugs or immunizations were prescribed or continued, lab and other types of tests were 

ordered or administered, and health education was documented.
NCHS Data Brief ■ No. 47 ■ October 2010

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Summary

This study describes primary care delivery across ambulatory care settings. Although the

majority of visits to primary care settings occur in physician offices (84%), OPDs and CHCs are

important sources of primary care for poor and uninsured populations.

CHCs also had a higher percentage of visits by patients with one or more chronic conditions 

compared with office-based physicians and OPDs. This higher burden may not be surprising,

as there are well-established associations between socioeconomic status and health (8). Although

OPDs and CHCs serve patients from similar neighborhoods and with similar sources of payment, 

OPDs receive fewer visits by patients with chronic disease. These observations may reflect true

differences in case mix or differences in awareness or documentation of chronic disease 

across settings.

The higher percentage of hospital OPD visits in which imaging and nonmedication treatment was

ordered or provided compared with physician offices and CHCs may be due to greater access

to these services in a hospital setting. Additionally, our analysis suggests OPDs serve a critical

complementary function to CHCs by providing care for acute conditions. These findings are

consistent with the role of CHCs and OPDs in the health care safety net (9–12).

Definitions

Community health center (CHC): An outpatient clinic that serves a medically underserved

population or is located in a medically underserved area. CHCs represented in NAMCS include

clinics that receive Section 330 grants under the Public Health Services Act, “look-alike” Health

Centers that meet Federally Qualified Health Center requirements, and Federally Qualified urban

Indian Health Service clinics (5).

Outpatient department: A hospital facility where nonemergent ambulatory medical care is

provided under the supervision of a physician.

Physician office: A place where nonfederally employed physicians provide direct patient

care in the 50 states and the District of Columbia, excluding radiologists, anesthesiologists, 

and pathologists.
NCHS Data Brief ■ No. 47 ■ October 2010

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Data sources and methods

All estimates are from the 2008 National Ambulatory Medical Care Survey (NAMCS) and

the National Hospital Ambulatory Medical Care Survey (NHAMCS). NAMCS is an annual

nationally representative survey of visits to nonfederal office-based physicians in the United

States. Starting in the 2006 data year, the NAMCS sample includes a separate stratum of

CHCs that includes physicians and nonphysician clinicians. NHAMCS is an annual nationally

representative survey of visits to nonfederal, general and short-stay hospital emergency and 

OPDs. More details about NAMCS and NHAMCS methodology are available (5–7).

In this report, physician and OPD visits were based on physician or clinic specialty; OPD clinics 

were selected based on a review of the clinic’s description (7). All CHC visits were included

except visits to providers seeing only patients with mental disorders or substance abuse. CHC and 

OPD visits include visits to both physicians and nonphysician clinicians (physician assistants, 

nurse practitioners, and nurse midwives). Comparable information on visits to nonphysician 

clinicians is underrepresented in the NAMCS compared with hospital OPDs and CHCs (13). 

However, analysis of these data after excluding visits to nonphysician clinicians yielded nearly 

identical patterns of care to those presented.

Data analyses were performed using the statistical packages SAS version 9.2 (SAS Institute,

Cary, N.C.) and SUDAAN version 9.0 (Research Triangle Institute, Research Triangle Park,

N.C.). Differences by site of care and selected patient and visit characteristics were examined 

using t-tests for differences in rates and Chi-square tests for differences in percent distributions at 

the p=.05 level.

About the authors

Esther Hing and Sayeedha Uddin are with the Centers for Disease Control and Prevention’s

National Center for Health Statistics, Division of Health Care Statistics. 
NCHS Data Brief ■ No. 47 ■ October 2010

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References

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health in a new era. National Academy Press, Washington, DC: 1996. http://books.nap.edu/

openbook.php?record_id=5152, last accessed July 7, 2010.

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last accessed July 7, 2010.

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Health Center data from the 2006–2008 National Ambulatory Medical Care Survey. Hyattsville,

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7.	 National Hospital Ambulatory Medical Care Survey. Public Use Data File Documentation. 

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Health Statistics. 2010.

8. Marmot M Wilkinson RG (eds). Social Determinants of Health, Oxford University Press,

New York: 1999.

9.	 Taylor J. The Fundamentals of Community Health Centers. National Health Policy Forum

Background Paper. The George Washington University. Washington, DC. August 31, 2004.

10.	Regenstein M, Huang J. Stresses to the Safety Net: The Public Hospital Perspective. The

Kaiser Commission on Medicaid and the Uninsured. June 2005.

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

United States, 2005–06. National Center for Health Statistics. Vital Health Stat 13(166). 2008.

12.	Forrest CB, Whelan EM. Primary care safety-net delivery sites in the United States: A

comparison of community health centers, hospital outpatient departments, and physicians’ offices. 

JAMA; 284(16):2077–83. Oct 25, 2000.

13.	Morgan PA, Strand J, Ostbye T, Albanese MA. Missing in action: Care by physician

assistants and nurse practitioners in national health surveys. HSR 42(5): 2022–37. 2007.
NCHS Data Brief ■ No. 47 ■ October 2010

Suggested citation

Hing E, Uddin S. Visits to primary care

delivery sites: United States, 2008. NCHS

data brief, no 47. Hyattsville, MD: National

Center for Health Statistics. 2010.

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source, however, is appreciated.

National Center for Health 

Statistics

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Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Health Care Statistics

Jane E. Sisk, Ph.D., Director

U.S. Department of

Health & Human Services

Centers for Disease Control and Prevention

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