National Ambulatory Care Medical Survey Methods:
What Clinicians Need to Know
Release Date: January 1, 2007
Expiration Date: December 31, 2009

Richard Niska, MD, MPH
David Woodwell, BA
Kathryn Porter, MD, MS
Beth Han, MD, PhD, MPH, MA
Donald Cherry, MS
Robin Remsburg, APRN, PhD
National Center for Health Statistics

Mary Lambert, RN, BSN, MN
Coordinating Center for Health Information and Service

Centers for Disease Control and Prevention (CDC)

CDC, our planners, and our content experts wish to disclose they have no financial interests or other relationships with the manufacturers of commercial products, suppliers of commercial services, or commercial supporters.

Presentations will not include any discussion of the unlabeled use of a product or a product under investigational use.

Instructions for Completing This Continuing Professional Education Activity

This program is set up to introduce key concepts in short written sections, punctuated by quiz questions to test your knowledge of the concepts just introduced. Please read each section, and then choose your answer to the quiz questions as you go. The answer key is at the end of this activity.

After the written material is reviewed, there is an abstraction exercise where you will be able to complete the survey instrument using a patient chart from your own records, and an evaluation form to help us improve this activity in future editions. Instructions for completing these are included below.

This activity has been developed for physicians and nurses.
CDC is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

CDC designates this educational activity for a maximum of 1.25 of category 1 credits toward the AMA Physician's Recognition Award. Each physician should claim only those credits that he/she actually spent in the activity.

This activity for 1.4 contact hours is provided by CDC, which is accredited as a provider of continuing education in nursing by the American Nurses Credentialing Center's Commission on Accreditations.

CDC has been reviewed and approved as an Authorized Provider by the International Association for Continuing Education and Training (IACET) 1620 I Street, NW, Suite 615, Washington, DC 2006. CDC has awarded 0.1 CEU's to participants who successfully complete this program.

Objectives

• Describe the methods for the National Ambulatory Medical Care Survey.
• Describe how complex survey designs can yield reliable estimates from small samples.
• Identify the strengths of National Center for Health Statistics survey designs and methods.
• Identify the limitations of National Center for Health Statistics survey designs and methods.
• List examples of health care survey findings used to influence physician practice.
• Describe the impact of nonresponse on the accuracy of the findings.
• Describe how the Centers for Disease Control and Prevention ensures confidentiality and complies with the Health Insurance Portability and Accountability Act in its national health surveys.

History and Background

The National Ambulatory Medical Care Survey (NAMCS) was initiated by the National Center for Health Statistics in May 1973 to gather and disseminate statistical data about medical care provided by office-based physicians to the population of the United States. The need for such a data collection system had been recognized many years before, having been pointed out as early as 1953 by the Subcommittee on National Morbidity Surveys of the U.S. National Committee on Vital and Health Statistics. Feasibility studies and field tests were conducted between 1968 and 1971, in which different data collection forms and procedures were tested. In addition to extensive consultation with experts in medicine and statistics, three major national pilot studies and several small area studies were employed in developing the NAMCS instruments and procedures. Through this process, these materials were refined to request only information considered essential to describe the utilization of ambulatory services and to require a minimal amount of time for the participating physicians. In its 1992 study, Toward a National Health Care Survey: a Data System for the Twenty-first Century, the Institute of Medicine endorsed “the National Center for Health Statistics plan to conduct the provider surveys on an annual basis.”

The NAMCS was conducted from 1973 through 1981, in 1985, and from 1989 onward as an annual survey. The breaks in data collection from 1982–1984 and 1986–1988 were due primarily to budget constraints. Except for those breaks, it has been conducted annually, yielding a database that permits analysis over more than 30 years.

The purpose of the NAMCS is to meet the needs and demands for statistical information about the provision of ambulatory medical care services in the United States. Ambulatory services are rendered in a wide variety of settings, including physician offices and hospital outpatient and emergency departments. Since more than 80 percent of all direct ambulatory medical care visits occur in physician offices, the NAMCS provides data on the greatest part of this sector of medicine. If NAMCS data were not collected, there would be a no national estimates on the content of physician office visits. Each year, the NAMCS provides baseline data on characteristics of the users and providers of physician office-based care. Data collected include patient demographics, reasons for visits, diagnoses, diagnostic services, medications, and disposition. These annual data, together with trends from other years, may be used to understand health care practice, identify and track problems, identify inequalities in the provision of health care services, establish national priorities, serve as comparison points for states, and measure Federal health guidelines such as the Healthy People objectives.

The NAMCS is part of the ambulatory care component of the National Health Care Survey, which is a family of surveys that captures health care utilization in settings such as outpatient, hospital inpatient and long-term care facilities. To complement the NAMCS, the National Center for Health Statistics initiated the National Hospital Ambulatory Medical Care Survey to provide data on patient visits to hospital outpatient and emergency departments. For the last ten years, the National Center for Health Statistics surveys of health care providers, including the NAMCS, National Hospital Ambulatory Medical Care Survey, National Hospital Discharge Survey, National Nursing Home Survey, National Health Provider Inventory, National Home and Hospice Care Survey and National Survey of Ambulatory Surgery have been modified and expanded into an integrated National Health Care Survey approach.

Q1: Why was the NAMCS initiated?
a. to gather and disseminate data about medical care in US physician offices
b. to do government feasibility studies
c. to serve as a publication mechanism for federal employees
d. to test different data collection instruments

Q1 Answer:
(a) The NAMCS was initiated to gather and disseminate statistical data about medical care provided at visits to office-based physicians in the United States. Feasibility studies and testing of data instruments were performed as part of the development of the NAMCS. Data from the survey have been used by both federal and non-federal researchers in studying questions of interest to the peer-reviewed literature. Examples of these studies are in this continuing education activity.

Q2: How often has the NAMCS been conducted since 1989?
a. Occasionally, when funding has been available
b. Annually
c. Every two years
d. The NAMCS was discontinued in 1989.

Q2 Answer:
(b) The NAMCS was first initiated in May of 1973. Between 1973 and 1989, there were six years when the survey was not funded. Since 1989, however, the survey has been conducted annually.

Q3: The NAMCS is part of the ambulatory care component of what larger survey?
a. National Health Service Corps Survey
b. National Health Care Survey
c. National Center for Health Statistics Survey
d. National Hospital Ambulatory Care Medical Survey

Q3 Answer:
(b) The NAMCS is part of the National Health Care Survey, as is the National Hospital Ambulatory Medical Care Survey. The National Center for Health Statistics and National Health Service Corps are federal agencies that conduct a variety of surveys as part of their missions.

Law Authorizing CDC to Conduct National Health Care Surveys

The National Center for Health Statistics (NCHS) is the nation’s principal statistical agency and is part of CDC's. It has the legal authority to collect health statistics as defined in the Public Health Service Act, Title 42, United States Code 242k, Section 306(a). The code states that NCHS shall collect statistics on a wide variety of health issues, including illness and disability in the population and the utilization of health care. Information on ambulatory health services is specifically mentioned in the legislation and is to be gathered and described by health professionals’ specialties and type of practice.

Confidentiality

The confidentiality of the data is protected by the Public Health Service Act, Title 42, United States Code 242m, Section 308(d). The code states that:

"No information, if an establishment or person supplying the information or described in it is identifiable, obtained in the course of activities undertaken or supported under section 306, may be used for any purpose other than the purpose for which it was supplied unless such establishment or person has consented (as determined under regulations of the Secretary) to its use for such other purpose and (1) in the case of information obtained in the course of health statistical or epidemiological activities under section 306, such information may not be published or released in other form if the particular establishment or person supplying the information or described in it is identifiable unless such establishment or person has consented (as determined under regulations of the Secretary) to its publication or release in other form..."

In addition, legislation covering confidentiality is provided according to section 513 of the Confidential Information Protection and Statistical Efficiency Act (PL 107-347), which states:

“Whoever, being an officer, employee, or agent of an agency acquiring information for exclusively statistical purposes, having taken and subscribed the oath of office, or having sworn to observe the limitations imposed by section 512, comes into possession of such information by reason of his or her being an officer, employee, or agent and, knowing that the disclosure of the specific information is prohibited under the provisions of this title, willfully discloses the information in any manner to a person or agency not entitled to receive it, shall be guilty of a class E felony and imprisoned for not more than 5 years, or fined not more than $250,000, or both.”

The records are also covered under the Privacy Act System of Records 09-20-0167, Health Resources Utilization Statistics. The NAMCS is designed so that NCHS receives no patient names, Social Security numbers, or health identification numbers. The top section of each patient record form, which contains the patient's name and record number, is separated from the bottom section by a perforation. The top section remains attached to the bottom until the entire patient record form is completed. Before collecting the completed patient record form, the top section is detached and given to the physicians or their staff to ensure confidentiality. The field representative instructs the physician to keep this portion for four weeks, in case it is necessary to retrieve missing information or clarify information that had been recorded.

Therefore, information collected in the survey is used only for statistical purposes. No information that could identify a person or establishment can be released to anyone - including the President, Congress, or any court, without the consent of the provider. The Census Bureau field representatives, who are collecting the data, sign an affidavit making them subject to the Privacy Act, the Public Health Service Act and other laws that require the data be protected. The National Center for Health Statistics and the Census Bureau maintain a perfect record in protecting the privacy of health care providers and patients.

HIPAA

The Health Insurance Portability and Accountability Act of 1996 (HIPAA) Privacy Rule (45 CFR 164.512) applies to data collected for the NAMCS. The Privacy Rule permits physicians and hospitals to make disclosures of protected health information without patient authorization, for public health purposes or for research that has been approved by an Institutional Review Board (IRB) with a waiver of patient authorization.

Before 2003, the NAMCS was exempted from IRB review because physician practices were not considered to be human subjects, the medical record data already existed, and no patient identifiers were collected. But with the implementation of the Privacy Rule in April 2003, a full IRB review of the NAMCS protocol was required.

The NCHS Research Ethics Review Board, which serves as an IRB, reviews the NAMCS protocol annually. The approval letter from the Ethics Review Board can be found on the Web at http://www.cdc.gov/namcs. The Board has granted (1) a waiver of the requirement to obtain informed consent from the patient, (2) a waiver of the documentation of informed consent by physicians, and (3) a waiver of patient authorization for release of patient medical record data by health care providers.

Q4. What laws authorize the National Center for Health Statistics to conduct national health care surveys?
a. National Health Survey Act
b. Public Health Service Act
c. Health Protection Act
d. Freedom of Information Act

Q4 Answer:
(b) The National Center for Health Statistics has the legal authority to collect health statistics as defined in the Public Health Service Act, Title 42, United States Code 242k, Section 306(a).

Q5. The National Center for Health Statistics will release identifiable health information only if the agency receives a:
a. Consent from the person or entity whose health information will be disclosed
b. Freedom of Information Act request
c. Court ordered subpoena
d. Patriot Act investigation

Q5 Answer:
(a) No one can get private data from the National Center for Health Statistics without the consent of the establishment or person. This means the National Center for Health Statistics can not give records to the police, military, courts, or any branch of government for whatever reason.

Q6. The National Center for Health Statistics Ethics Review Board granted waivers for all of the following EXCEPT:
a. the requirement to obtain informed consent from the patient
b. the documentation of informed consent by physicians
c. future Ethics Review Board review
d. patient authorization for release of patient medical records

Q6 Answer:
(c) The National Center for Health Statistics Ethics Review Board reviews the NAMCS protocol annually.

Methods

The NAMCS uses a multistage sampling design with the elementary sampling unit being a physician patient encounter or "visit." The first stage of selection is a probability sample of 112 geographic primary sampling units which comprise a subset of the 1985-94 National Health Interview Survey primary sampling units. Within primary sampling units, physicians are stratified into 14 major specialty groups and an additional catch-all group for other specialties. This assures that physicians within each of these specialty groups are selected in the sample. Within each specialty stratum, a systematic random sample of physicians is selected. The total physician sample is divided into 52 sub-samples that are randomly assigned to the 52 weeks of the year. Each physician's practice is sampled by randomly assigning a one week data reporting period during the calendar year, and by selecting a systematic random sample of approximately 30 patient visits during the assigned week. Substitution of the reporting week is not permitted. This provides for continuous data collection throughout the year to account for seasonal variation in disease and patient visit patterns. Data collection within a physician's practice begins on Monday morning of the assigned reporting week and continues through the following Sunday. Visits are recorded on a "Patient Visit Worksheet." This worksheet allows the office staff to easily keep track of the patients as they enter the office and select (through the sampling plan) those that will fall into the survey sample.

Data is collected by field representatives from the Bureau of the Census, through an interagency agreement with CDC. Physicians who have been selected to participate in the survey receive an introductory letter, signed by the Director of NCHS, approximately three weeks before their reporting period is to begin. This letter explains the basics of the survey, that participation is voluntary, and that a Census Bureau field representative will contact them shortly to further explain the survey. We include a motivational brochure with the introductory letter. This short brochure contains reasons for participation, and questions and answers on confidentiality issues including the HIPAA Privacy Rule. In addition, the envelope contains endorsing letters from medical specialty associations and other professional and trade organizations.

The introductory letter is followed by a telephone call to the physician from the Census Bureau field representative to schedule a personal interview so that the physician can be inducted into the NAMCS sample. During the induction visit, the interviewer provides the physician, nurses and staff with verbal and written instructions on the completion of patient records. At this time the interviewer also instructs the physician, nurses and staff on the sampling procedures, which vary according to how many visits the physician expects to see during the sample week. Printed on the folder are general instructions and definitions for easy reference. More detailed definitions and instructions for selected Patient Record Form items are provided on a printed card placed in a pocket of the folder. While the Census field representatives can abstract the medical records onto the patient record form themselves, many physicians prefer the added confidentiality safeguard of performing the abstraction themselves or having their nurses or office staff do so.

A Physician Induction Interview form is completed for each sampled physician during the induction visit. The questions in the first-half of the physician induction interview are used to guide the field representatives through the induction process and verify the physician's eligibility. The second half of the form is dedicated to obtaining information concerning selected practice characteristics. During the week after the physician's reporting period, the field representative returns to the office to retrieve all completed survey materials and to do a brief edit of the patient record forms. Attempts are made while in the physician's office to retrieve missing data, correct inconsistencies, and clarify unclear entries directly with the responding physician and his or her nurses or staff.

The major portion of the data collection occurs with the completion of patient record forms by the sampled physician, office nurses or staff, or Census field representative. A random “start with” number is provided to each physician (e.g. “start with the fifth chart on the list”) after whom every nth patient (e.g. “take every fifth chart”) is sampled throughout the 7-day reporting period. Based on this algorithm, the physician, nurse or staff records each patient visit in sequence during the reporting week and completes patient record forms for the designated sample visits. We provide a worksheet in the back of the Patient Record Form Instruction Booklet to guide through this process. The patient visit sample size is assigned to physicians according to practice size so that about 30 patient record forms will be completed during the reporting week.
Data on patient characteristics (like age, sex, race and ethnicity), visit characteristics (such as date and source of payment), reason for the visit in the patient’s own words, up to three primary and secondary diagnoses, and medications mentioned, are recorded on the NAMCS patient record form.

Q7: The elementary sampling unit for the NAMCS is the:
a. physician
b. physician-patient encounter (visit)
c. patient
d. physician’s practice

Q7 Answer:
(b) The NAMCS uses a multistage sampling design with the elementary sampling unit being a physician patient encounter or "visit." The selection stages leading up to that are the geographic primary sampling units, physician specialty groups, individual physicians, and then about 30 patient visits during the assigned week.

Q8: Data collection for the physician’s practice begins on:
a. Monday and continues to the following Sunday
b. January 1st and continues through January 7th
c. Day one of the assigned month and continues through last day of the month
d. Randomly assigned day and continues for 7 days

Q8 Answer:
(a) Within one of 52 randomly assigned weeks, data collection begins on Monday and continues to the following Sunday.

Q9: The questions in the Physician Induction Interview are used to:
a. Guide the Field Representative through the interview process
b. Verify the physician’s eligibility
c. Obtain information on selected practice characteristics
d. All of the above

Q9 Answer:
(d) The Physician Induction Interview is used by the field representative a guide while interviewing the physician. Questions are included about eligibility criteria and practice characteristics.

Q10: Which of these patient characteristics are recorded on the Patient Record Form?
a. Age, sex, race and ethnicity
b. Date of visit and source of payment
c. Diagnoses and medications provided or prescribed
d. All of the above

Q10 Answer:
(d) In addition to these choices, many other patient and visit characteristics are recorded on the Patient Record Form. One other example is the reason for the visit in the patient’s own words.

Q11: Which following statement about the NAMCS is true?
a. The NAMCS includes primary diagnoses at visits to U.S. physician offices.
b. The NAMCS includes secondary diagnoses at visits to U.S. physician offices.
c. The NAMCS provides major reasons for the visits to U.S. physician offices.
d. All of the above

Q11 Answer:
(d) The NAMCS includes up to three primary and secondary diagnoses related to visits to US physician offices. Also, the NAMCS provides major reasons for the visits to US physician offices.

Generalizability and Nonresponse

Since NAMCS responses are weighted according to the inverse probability of selection into the national sample, it is possible to make accurate inferences about ambulatory medical care throughout the nation. However, because our sample size is not large, each physician who does not respond has an impact on the accuracy and generalizability of the national estimates coming from this survey. Some demographic factors in nonresponse are controlled for in the analysis, such as physician specialty. But if nonresponse rates become too high within some strata, the quality of the data can be compromised significantly. Discussions of these issues, where they arise, are generally included in the appendices to the survey.

NAMCS participation is important because without it, physicians cannot benefit from being represented in the national description of office-based patient care. Physicians were randomly chosen to represent not only themselves but also other physicians in the same geographic region and medical specialty.

Q12: Why is it important for physicians to cooperate in the NAMCS?
a. In small samples, accuracy and generalizability can be affected by nonresponse.
b. In large samples, individual physician responses are unimportant.
c. Physicians can be sanctioned by Medicare for not participating.
d. Government authors will be more publishable with better response rates

Q12 Answer:
(a) Physician participation is important because the actual number of physicians sampled is small relative to the actual number practicing in the US. As such, each physician’s participation represents many other practicing physicians in the same geographic area and specialty. Each time a physician declines to participate, the national visit estimates produced are not as accurate if there were 100% participation. Although the NAMCS sample is relatively small, individual responses are never considered unimportant, even in larger surveys. While better response rates contribute to publication success for both federal and non-federal researchers, this is not the prime reason for encouraging participation. There are no penalties for nonresponse from Medicare or any other organization.

Usefulness of Data to Outside Users

The list of NAMCS data users is extensive. It includes physicians engaged in clinical care and research, hospital administrators, health care consultants, advocacy groups and students. Other users include medical planners trying to determine the need for physician services in a particular area of the country, pharmaceutical firms engaged in drug research, medical libraries, academic researchers and private companies. Other Federal agencies use NAMCS data, such as the National Institutes of Health, National Center for Chronic Disease Prevention and Health Promotion, and the Government Accountability Office. NAMCS data are often quoted by the broadcast and print media, such as the ABC Evening News, Redbook magazine, the Washington Post, the Atlanta Constitution, US News and World Report, CNN, and the Wall Street Journal.

The resulting published statistics help professionals plan for more effective health services, improve medical education, and assist the public health community in understanding the epidemiology of diseases and health conditions. The continuing nature of the survey permits observation and measurement over time of different ways of managing and treating patient problems. In addition, it provides valuable general information on the etiology and epidemiology of selected conditions, the speed and effectiveness with which advances in medical practice are adopted, and the effectiveness of educational programs among office-based physicians.

Q13: Name some of the non-Federal users of NAMCS data:
a. Clinicians
b. Academic researchers
c. Medical libraries
d. All of the above

Q13 Answer:
(d) Other possible responses include hospital administrators, health care consultants, advocacy groups, medical planners trying to determine the need for physician services in a particular area of the country, pharmaceutical firms engaged in drug research, and many others.

Q14: Who are some of the Federal users of NAMCS data?
a. National Institutes of Health
b. National Center for Chronic Disease Prevention and Health Promotion
c. Government Accountability Office
d. All of the above

Q14 Answer:
(d) The National Institutes of Health, the National Center for Chronic Disease Prevention and Health Promotion and the Government Accountability Office are only three of the federal organizations that make use of NAMCS data.

Practical Examples of NAMCS Survey Results

Since NAMCS data provide such an important tool for tracking utilization of U.S. ambulatory health care, a large body of medical literature based on this data has developed over the 32-year history of the survey. To illustrate the practical uses that can be made of the type of data that practicing clinicians can provide, we present here three examples of studies from the peer-reviewed literature that give a sense of how common problems are diagnosed and managed by clinicians across the nation.

Plantar Fasciitis

The first study (1) gives national estimates on the frequency of visits for plantar fasciitis in office practices and hospital outpatient departments, what kinds of physicians typically see this problem, and what is done for it by most physicians.

Although the sample size included only 280 sites (170 office-based physicians and 110 outpatient departments), the multi-stage representative sampling design made possible an accurate extrapolation to the entire nation. Thus, it was determined that a little over one million visits are made to physicians for plantar fasciitis each year. However, with such a small sample size, nonresponse from survey participants (ranging from 27% to 37% over the six years of NAMCS data in this study) can have a real impact on the accuracy of the results. Although statistical adjustments can be made to adjust for nonresponse, that does not substitute for collecting real data from practicing clinicians.

This study showed that 62% of visits for plantar fasciitis are made to primary care physicians, and 31% to orthopedic surgeons. Because the NAMCS categorizes physicians into 15 specialty areas, it is possible to gain an accurate view of specialty utilization for most medical problems, and especially to track the relative use of primary care versus subspecialty physicians for problems that might otherwise be considered to be in the exclusive domain of the subspecialty. Another useful piece of information is how frequent visits for any one diagnosis might be in a typical physician’s practice. In this study, for example, it was determined that 1% of an orthopedic surgeon’s practice consists of plantar fasciitis. For medical students trying to gain an accurate view of what a particular specialty might be like, national estimates of diagnosis visit frequencies would provide valuable career information.

One limitation brought up in this study was that podiatrists were not included in the NAMCS sample, while other literature (and common sense) suggests that the NAMCS estimate of plantar fasciitis visit frequency might be artificially low. This is one example of how the scientific literature should be read critically, taking both strengths and limitations of a study into account.

Although the NAMCS does not in any way define the acceptable standard of care for any diagnosis, it can provide national estimates of what is actually done in practice. In this study, 47% of patients were treated with non-steroidal anti-inflammatory drugs, and 26% received counseling on exercise. The authors note that neither of these interventions has been rigorously studied for efficacy. This would have practical implications for physicians validating their own practice styles against that of other clinicians, or for suggesting future research directions for randomized clinical trials that might offer objective evidence either for or against continuing a common practice.

Q15: What is the potential impact of nonresponse on national estimates derived from a small sample size, such as the 280 clinics sampled in this study?
a. The impact of nonresponse is negligible, as the central limit theorem requires a sample size of only 30 in order to yield significant results.
b. It is not possible to derive meaningful national estimates with a small sample size.
c. The impact is significant, because nonresponse in a small sample can reduce the accuracy of results extrapolated to all outpatient facilities in the nation.
d. The impact is negligible, because statistical adjustments substitute for real data.

Q15 Answer:
(c) The impact on nonresponse in a small sample is significant. Although the requirements of the central limit theorem are exceeded in this study, and although statistical adjustments can be made in weighting data to account for nonresponse, none of these substitutes for real data derived from a larger number of respondents.

Q16: Which statement about specialty data in the NAMCS is false?
a. It is possible to study the frequency of many diagnoses seen in ambulatory care practices by physicians in 15 different specialties.
b. National prevalence estimates of diagnoses are possible in the NAMCS.
c. It is possible to study primary care versus subspecialty utilization in the NAMCS.
d. Specialty utilization information can be valuable for medical students and residents trying to make career choices.

Q16 Answer:
(b) Since the NAMCS is based on visits rather than individual patients, diagnosis frequencies do not constitute disease prevalences.

Q17: Which statement about specialty data in the NAMCS is true?
a. Data for non-physician providers, such as podiatrists, are not collected.
b. Since physicians see most medical problems, inclusion of other health care providers does not affect visit frequencies for most diagnoses.
c. Since NAMCS is fielded by CDC, critical reading of its literature is unnecessary.
d. Podiatrists are included in the orthopedic surgeon category in the NAMCS.

Q17 Answer:
(a) Data are not collected in the NAMCS for several non-physician provider categories, such as podiatrists, dentists and nurse practitioners. This can be a significant limitation for many diagnoses, such as plantar fasciitis in the case of podiatrists. Regardless of the prestige attributed to any research institution, limitations exist in any scientific study. Thus, a critical understanding of those limitations is always necessary in interpreting studies from any source.

Q18: Which statement about medical standards of care is true?
a. Since the NAMCS collects national data on physician treatments for diseases, it is possible to define acceptable standards of care from this data.
b. The NAMCS looks at the efficacy of treatments for disease, such as the use of anti-inflammatory medication in plantar fasciitis.
c. While a definition of standards of care is not appropriate from NAMCS data, the survey does provide national data on what is actually done in practice.
d. The NAMCS is a randomized clinical trial of disease treatments.

Q18 Answer:
(c) The NAMCS is a physician office survey that does collect treatment information, but there is no randomization applied to diseases or their therapies. No efficacy data is collected either. Since the NAMCS does study how physicians actually treat diagnoses, it is possible to provide national data on what occurs in practice. However, there is no assurance from this data that such practices conform to any guideline or standard of care.

Diet and Physical Activity Counseling During Ambulatory Care Visits

Cardiovascular disease is the number one cause of death in the US. Many risk factors, such as smoking, hypertension, hyperlipidemia, diabetes mellitus and obesity, are preventable and modifiable by engaging in healthy dietary patterns and adequate physical activity. However, national data have shown an increased prevalence of people with these risk factors over the past decade. Since 80% of Americans regard their physicians as the primary source of information about health, behavioral counseling by physicians is a critical opportunity for patients to understand risk factors and to modify their lifestyles.

Little is known about national patterns of behavioral counseling on diet and physical activity during ambulatory care. One study (2) used the 1992-2000 NAMCS and National Hospital Ambulatory Medical Care Survey to provide national estimates of counseling practices in U.S. private physician offices and hospital outpatient departments. This study found that rates of diet and physical activity counseling among visits by at-risk adults showed a modest ascending trend from 1992 to 2000, with the biggest growth found between 1996 and 1997. However, throughout the 1990s, diet counseling was provided in less than 45% of visits, and physical activity counseling in less than 30% of visits by adults with diagnoses of hyperlipidemia, hypertension, obesity, or diabetes.

Several national guidelines have been developed to guide the prevention and treatment of modifiable cardiovascular disease risk factors in clinical settings.(3)(4)(5)(6) Behavioral counseling to promote healthy eating and active living is a commonly recommended preventive measure, especially for patients with elevated cardiovascular disease risk. Despite these national recommendations, this study revealed that behavior counseling about diet and physical activity remained below expectations during outpatient visits by adults with an elevated cardiovascular disease risk.

One of the main strengths of this study is the use of two large national data sets over several years. Furthermore, it examined not only time trends but also independent correlates of diet and physical counseling for adults with cardiovascular disease risk. The study had limitations as well. Both the NAMCS and National Hospital Ambulatory Medical Care Survey are serial, cross-sectional surveys of patients visits, but it is impossible to ascertain whether multiple visits by the same patient were made, based on the secondary data. Also, documentation of patient counseling tends to be underreported in the medical records utilized by NAMCS. For both these reasons, actual patient exposure to behavioral counseling over time may be underestimated. Moreover, neither NAMCS nor the National Hospital Ambulatory Medical Care Survey provides information on the appropriateness, content, or intensity of diet and activity counseling.

However, this study clearly indicates that there are many missed opportunities for diet and physical activity counseling during ambulatory care visits by US adult patients with elevated risk for cardiovascular disease. Furthermore, counseling rates are disproportionately lower in older patients and patients treated by primary care physicians. Therefore, primary care physicians, particularly, need to improve their clinical practice of preventive counseling for older patients with elevated cardiovascular disease risk factors.

Q19: Which of the following statements about NAMCS health education data is true?
a. Data cover the appropriateness of health education.
b. Data cover the duration of health education.
c. Neither a nor b
d. Both a and b

Q19 Answer:
(c) Neither the appropriateness nor the duration of health education services is covered, only whether health education was provided.

Q20: What kind of office-based interventions are studied in the NAMCS?
a. Specific diets and exercise regimens
b. Complementary and alternative weight loss plans
c. Counseling on lifestyle issues such as diet and physical activity
d. Lifestyle counseling is too under-reported to be of any use in this survey.

Q20 Answer:
(c) The NAMCS studies a number of counseling interventions during physician office visits, including diet and exercise recommendations. However, data on specific diets or exercise programs, whether mainstream or alternative, are not collected. While under-reporting of patient counseling in medical records is an issue, useful research has been published using both the NAMCS and National Hospital Ambulatory Medical Care Survey data sets.

Antibiotic Resistance

Antibiotic resistance has been called one of the world's most pressing public health problems. Over the past decades, bacteria have developed resistance to antibiotics developed to control infection. Virtually all important bacterial infections in the United States and throughout the world are becoming resistant to first-line therapies. For this reason, antibiotic resistance is among CDC’s top concerns. Antibiotic prescribing patterns in the United States has been reported on the NAMCS, allowing researchers to define the extent of prescribing and describe trends over time.

Data from NAMCS showed that antimicrobial prescribing rates for children by physicians in office-based practices in the United States increased by 48% from 1980 through 1992.(7) Many public health and professional organizations launched campaigns and interventions to promote appropriate antimicrobial use. Decreasing inappropriate antibiotic use is the best way to control resistance. Children are of particular concern because they have the highest rates of antibiotic use. They also have the highest rate of infections caused by antibiotic-resistant pathogens.

To evaluate the impact of these campaigns, researchers at CDC analyzed NAMCS data from 1989 though 2000 to assess prescribing rates overall and for respiratory tract infections for children and adolescents under 15 years.(8) A total of 17,853 physicians participated in the survey during this time, and response rates varied by data collection year from 65% to 74%. Researchers found that the average population-based annual rate of antimicrobial prescriptions per 1000 persons studied decreased from 838 in 1989-90 to 503 in 1999-2000. The visit-based rate decreased 29% from 330 to 234 per 1000 office visits during the same period. For selected infections of the respiratory tract (i.e. otitis media, pharyngitis, sinusitis, bronchitis and upper respiratory infection), the visit-based rate decreased 14% from 715 to 613 per 1000 visits during the study period.
The NAMCS has served as the principal source of trend data for office-based prescribing rates by physicians in the United States. The survey will continue to be a useful tool in the evaluation of ongoing efforts to prevent unnecessary use of antibiotics.

Q21: NAMSC data were useful in the evaluation of antibiotic prescribing patterns by office-based physicians because they showed:
a. Trends population-based and visit-based prescribing rates over time
b. Medication errors for specific illnesses
c. Adverse events associated with antibiotic prescribing
d. Adherence to practice guidelines set forth by the Agency for Health Care Research and Quality

Q21 Answer:
(a) The NAMCS is the main source of trend data for office-based prescribing by U.S. physicians. A major limitation, however, is that the appropriateness of an antimicrobial prescription can not be assessed from the data collected.

Survey Strengths and Limitations

These research examples demonstrate some of the strengths and limitations of using NAMCS data. Some strengths include: (1) being the only national instrument that collects data on patient visits to physicians; (2) the ability to ascertain the actual amount of health care utilization versus depending on more subjective assessments; (3) the ability to identify and track treatment patterns for various disorders, medications, procedures and diagnostic tests; (4) the ability to track visits by various characteristics over time; and (5) providing a data source that sparks new ideas for future research.

The NAMCS is not without some limitations, such as: (1) a relatively small sample – only 3000 physicians per year; (2) few outcome measures – we don’t know if a patient gets better or worse after a particular treatment; (3) limited ability to make estimates about rare events – multiple year data must be combined for relatively rare conditions such as HIV; (4) being a cross-sectional look at one episode of illness – no way of tracking patients from the first time they develop a symptom to the completion of treatment, or of knowing what prior treatments were effective or not; (5) unavailability of data on care from other medical care providers outside the physician’s office; and (6) inability to make prevalence estimates, since the survey is based on visits and not individual patients.

Q22: Name some strengths of the NAMCS.
a. Only national survey that collects medical data at the time of the patient visit
b. Provides actual health care utilization assessment
c. Can identify treatment patterns
d. All of the above

Q22 Answer:
(d) Other strengths of the NAMCS include the ability to track aggregate visits for various medical conditions over time, and being a source of future research ideas.

Q23: Name some limitations of the NAMCS.
a. Relatively small sample size (3,000 physicians each year)
b. No outcome measures
c. Multiple year data must be combined for certain rare conditions
d. All of the above

Q23 Answer:
(d) Other limitations of the NAMCS include inability to determine the episode of an illness on a time continuum, missing of non-physician care (podiatrists, dentists and other professions), and inability to provide disease prevalence estimates.

Abstraction Exercise

This exercise is provided in order for you to gain a practical sense of how patient visit data is collected in the NAMCS. To begin, please select a patient record from your office files. You will be abstracting data from this record onto the Patient Record Form for the 2005 NAMCS. To obtain the Patient Record Form, please click the link below to open NAMCS-30_2005.pdf.

NAMCS-30_2005.pdf (Opens in a new window).

In filling out this form, use only data that is actually recorded in the patient chart. This will give you a sense of the task faced by our field representatives, your office staff, or yourself if you are a participant in the actual survey.

Since the abstraction form is for one patient visit, select the patient’s most recent visit in the chart. Some general information (e.g. date of birth, sex, ethnicity) can be found in other areas of the chart. Other information (e.g. gestation status, reason for visit, diagnosis) will be specific to that visit. Continuity of care information (e.g. previous visits) will be recorded relative to the most recent encounter. More detailed instructions used by the Census Bureau field representatives are included here. Click the link below (Abstraction Exercise.pdf) to clarify any questions.

Abstraction Exercise.pdf (Opens in a new window)

Summary

Now that you have completed these activities, you should be better informed about the National Ambulatory Medical Care Survey. Specifically, you should be able to:
• Describe the survey methods for the National Ambulatory Medical Care Survey.
• Describe how the sample is defined in a complex survey design such as NAMCS.
• Identify the strengths and limitations of National Center for Health Statistics survey designs and methods.
• List examples of health care survey findings used to influence physician practice.
• Describe the impact of nonresponse on the accuracy of the findings. State the laws authorizing CDC to conduct national health care surveys, ensuring confidentiality, and operating under HIPAA.

Obtaining CE Credits

• Click the link to go to CDC Training and Continuing Education Online at http://www.cdc.gov/phtnonline.
• If you have not registered as a participant, click 'New Participant' to create a user ID and password; otherwise click 'Participant Login' and log in.
• Once logged in, you will be on the Participant Services page
• Click 'Search and Register'. Use one of the 3 search options, and click 'View'.
• Scroll down and click on the program title
• Click on the type of CE credit you would like to receive
• Click Submit.
• Answer the three demographic questions
• Click Submit.
• If you have already completed the course you may choose to go right to the evaluation
• Complete the evaluation and click Submit
A record of your course completion and your CE certificate will be located in the 'Transcript and Certificate' section of your record

If you have any questions or problems please contact:
CDC Training and Continuing Education Online
800-41TRAIN or 404-639-1292
Email at ce@cdc.gov

References

1. Riddle DL, Schappert SM. Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: a national study of medical doctors. Foot Ankle Int 2004; 25(8):303-10.

2. Ma J, Urizar GG, Alehegn T, Stafford RS. Diet and physical activity counseling during ambulatory care visits in the United States. Prev Med 2004; 39:815-822.

3. NCEP III. Third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III) final report. Circulation 2002; 106:3143-3421.

4. JNC VI. The sixth report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure. Arch Intern Med 1997; 157:2413-2446.

5. AACE/ACE Obesity Task Force. AACE/ACE position statement on the prevention, diagnosis, and treatment of obesity. Endocr Pract 1998; 4:297-330.

6. U.S. Preventive Services Task Force. Behavioral counseling in primary care to promote a healthy diet. Am J Prev Med 2003; 24:93-100.

7. McCaig LF, Hughes JM. Trends in antimicrobial drug prescribing among office-based physicians in the United States. JAMA 1995; 273:214-219.

8. McCaig LF, Besser RE, Hughes JM. Trends in antimicrobial prescribing rates for children and adolescents. JAMA 2002; 287:3096-3102.

Page Last Modified: December 18, 2006