http://informahealthcare.com/jdt ISSN: 0954-6634 (print), 1471-1753 (electronic) J Dermatolog Treat, 2014; 25(6): 453–458 ! 2014 Informa UK Ltd. DOI: 10.3109/09546634.2014.858409
EDITORIAL
The National Ambulatory Medical Care Survey: A resource for understanding the outpatient dermatology treatment Christine S. Ahn1, Mary-Margaret Allen1, Scott A. Davis1, Karen E. Huang1, Alan B. Fleischer Jr.1, and Steven R. Feldman1,2,3 Department of Dermatology and 2Department of Pathology, and 3Department of Public Health Sciences, Center for Dermatology Research, Wake Forest School of Medicine, Winston-Salem, NC, USA Abstract
Keywords
Background: The National Ambulatory Care Survey (NAMCS) collects information on outpatient medical care in the United States. Key characteristics of the NAMCS methodology are not well recognized. We describe the NAMCS survey design and patient visits to dermatologists and to present information on the validity of the NAMCS data by comparing key features of the dermatologist sample to other surveys of dermatologists. Methods: NAMCS data on dermatologists and skin-related visits from 1993 to 2010 were analyzed and compared to the Dermatology Physician Profile Survey (DPPS), a survey by the American Academy of Dermatology. Results: A total of 29 554 patient visits to dermatologists were sampled from 1993 to 2010. On average, 118 dermatologists were sampled annually to participate in the NAMCS, and response rates ranged from 47 to 77%. The NAMCS and the DPPS found similar dermatologist demographics, practice settings and reimbursement sources. Conclusion: Overall, the NAMCS achieves high-response rates and provides a generalizable sample that has been used in scores of studies of dermatology outpatient treatment. In a time of changing health care delivery systems, NAMCS is valuable for understanding how physicians care for patients with skin disease.
AAD, cutaneous, dermatologist, DPPS, NAMCS, skin
Introduction The practice of dermatology presents innumerable important clinical questions. Many of these questions are difficult or impossible to answer with prospective studies. Moreover, clinical trials do not answer questions about how medicine is actually practiced in the community. Retrospective studies have an important place in addressing many clinical issues. The strengths of retrospective designs include the relatively inexpensive cost, ability to analyze multiple outcomes, and the ability to analyze low-incidence diseases. These strengths can be used to answer a wide range of research questions, including critically important issues on what diseases are being treated and how the practice of dermatology is changing. The National Ambulatory Medical Care Survey (NAMCS) is a large, nationally representative survey of U.S. outpatient medical practice that has been used extensively to address questions involving the management of patients with skin disease. Previous studies that have used data from NAMCS do not provide extensive detail on the methodology of this survey; the accuracy of studies using the NAMCS depends on the representativeness of the sample of dermatologists who provide data.
Correspondence: Steven R. Feldman, MD, PhD, Department of Dermatology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. Tel: 336 716 7740. Fax: 336 716 7732. E-mail: [email protected]
History Accepted 21 October 2013 Published online 20 November 2013
The purpose of this study was to describe the NAMCS survey design, to describe patient visit characteristics to dermatologists by NAMCS data from 2005 to 2010, to validate the NAMCS by comparing characteristics of dermatologists surveyed in NAMCS from 2005 to 2010 to dermatologists surveyed in the Dermatology Physician Profile Survey (DPPS).
Methods NAMCS survey design
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1
The methodology of the NAMCS surveys was reviewed based on a methods template produced by the National Hospital Ambulatory Medical Care Survey (NHAMCS) staff that is recommended to be included in all NHAMCS publication. This was adapted to the methodology of NAMCS. Dermatologist and patient visit characteristics Data from the National Ambulatory Care Survey were analyzed from 1993 to 2010 to determine the sample sizes and response rates among dermatologists. To determine specific physician characteristics, data from 2005 to 2010 were analyzed, when the physician statistical weight was made available. The physician characteristics recorded by NAMCS include the type of doctor (MD or DO); employment status; and whether any home visits, hospital visits, or consults over the phone or e-mail were conducted within the previous week. Office-based information collected includes U.S. geographic location of the office; the
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metropolitan statistical area of the office; type of office; practice ownership; electronic medical record (EMR) usage; submission of claims electronically; percent of revenue from Medicare, Medicaid, private insurance, or other source; the number of managed care contracts; status of accepting new patients and if so, the types of payments accepted from these patients – capitated payment, non-capitated payment, Medicare, Medicaid, private insurance, worker’s compensation, self-pay, or no charge. For visit records, patient demographic information including age, sex, ethnicity, and race (un-imputed and imputed for missing responses) is recorded. In addition, the expected main type of payment (since 1997), whether the patient was new to the practice, and U.S. geographic location of the visit (Northeast, Midwest, South, West) are documented. Starting in 2006, data were collected to roughly indicate the socioeconomic status of patients seen by a physician. For each patient’s home zip code, the percent of people in poverty, median household income, percent of adults with a Bachelor’s degree, and urban/rural classification were identified. Comparison to the dermatology practice profile survey To evaluate the generalizability of NAMCS data on dermatologic services in the US, physician and outpatient visit characteristics of dermatologists reported by the NAMCS survey were compared to the results of the dermatology practice profile survey (DPPS) published by the American Academy of Dermatology (AAD). The DPPS, which is a national survey of practicing members of the AAD, surveys a stratified random sample of associates, life, and honorary Academy members. Members are excluded if they were international members, known retirees, and those older than 72 years. This survey, which was first administered in 2002, has been conducted every other year and collects information on the characteristics of dermatology practice, including practice activities, quality measures and systems, reimbursement sources, and insurance. Beginning in 2007, the survey also included sections pertaining to the use of physician assistants and nurse practitioners in dermatology practice (1). The results of the NAMCS from 2005 to 2010 were compared to results of the 2009 DPPS.
Results NAMCS survey design The NAMCS has been conducted annually since 1989 by the Center for Disease Control and Prevention’s National Center for Health Statistics (NCHS) branch. The survey samples outpatient visits to physicians and are defined as working ‘‘office-based’’ by the American Medical Association (AMA) or American Osteopathic Association (AOA). Federally administered practices (such as an outpatient military or Veterans Administration facility) are not included. The sample is selected using a threestage process: (i) 112 geographic areas (counties, townships, or equivalents of these areas) in the 50 states and District of Columbia are sampled; (ii) practicing physicians are sampled from master files maintained by the AMA and AOA after stratifying the lists by 15 physician specialties, including dermatology; (iii) for each physician, an approximately 1-week period from the year is randomly sampled, from which a portion of visits are systematically chosen. Sampling rates of visits during that week range from 20% for busy practices to 100% for less busy practices, producing around 20–30 visits for each office surveyed in a given year. Types of patient–physician contacts that are not included are consults over the phone, visits at institutions where the institution has primary responsibility for the patient, visits for administrative purposes, house-calls, or visits at a hospital. For each visit sampled, the physician, the physician’s staff, or a Census Bureau representative fill out a form based on medical
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records. Data collected include patient demographics, type of payer, reason for visit (from the patient’s perspective), diagnoses given at the visit (up to three), medications newly prescribed or continued, procedures performed, visit characteristics (i.e. counseling offered, screening tests given, time spent with the physician, and use of a physician extender at the visit), and office characteristics (i.e. use of EMRs, amount of revenue from different sources, and acceptance of new patients). Previous studies have examined the accuracy of the information recorded by the NAMCS by comparing the NAMCS measurement approach with other measures, including direct observation of outpatient visits and Centricity EMR databases (2,3). When NAMCS findings were compared to visit content measured by direct observation, the NAMCS physician report method was more accurate for reporting procedures and examinations. However, the NAMCS under-reported behavioral counseling (such as alcohol counseling and smoking cessation advice) and over-reported visit duration (2). In the comparison of NAMCS findings to Centricity EMR databases, the EMR data showed higher proportions of visits by younger patients and by females than data from the NAMCS, and demonstrated a higher sensitivity in capturing chronic diagnoses. This observation was thought to be due to the medical documentation requirements for the Centricity EMR, such as inclusion of laboratory results and medication information, in contrast to the NAMCS, which focuses on the primary reason for the office visit (3). Over the years, some survey items have been added, removed or modified, so care needs to be taken when combining multiple years of data together. Records are then processed by an independent center that classifies diagnoses, causes of injury, and procedures by the International Classification of Disease, 9th Revision, Clinical Modification (ICD-9CM) codes and reasons for visits using the Reason for Visit Classification for Ambulatory Care. Up until 2006, the Federal National Drug codes were used to classify medications; from 2006 and later, Multum’s Lexicon Drug database was used for medication classification (4). NCHS provides sample SAS code so that data users can modify medication classifications prior to 2006 to match the Multum’s Lexicon Drug database classification. The NAMCS data are de-identified and made freely available to researchers on the NCHS website in SAS, SUDAN, SPSS, and Stata format (5). In addition, tutorials are available on the website for researchers using the data. From 1993 and forward, masked patient visit weights and survey design items were made available so that researchers can produce accurate, unbiased national estimates. Survey visit weights correct for non-response rates after taking into account when (time of year) and where (geographic location and urbanization) visits were sampled. Starting in 2005, physician weights were also made available for physician-level analyses (this permits studies to answer questions such as ‘‘what percentage of dermatologists use an electronic medical record system?’’). Data can be combined with U.S. Census data to assess the number of visits per 100 000 population of a specific demographic, or with data on the number of licensed physicians to assess the average caseload within particular specialties. Dermatology visit characteristics On average, from 7931 dermatologists on the AMA and AOA physician master lists, 118 dermatologists were sampled each year, with 18% of those sampled not meeting eligibility criteria. The most common reasons for non-eligibility were physicians working in a hospital outpatient department, working in an institutional setting and being retired. Of those sampled that were eligible, 66% participated in the survey process (varying from 46.7% in 2009 to 77.1% in 1995). A total of 29 554 patient-visits to dermatologists were sampled and recorded from 1993 to 2010 (ranging from 1137 in 2009 to 2065 in 1994, Table 1).
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Table 1. Sampling and response rates of dermatologists for NAMCS survey, 1993–2010.
Year
Sampling poola
Total sampled
In-scopeb
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
6447 6445 6813 6900 7152 7572 7172 7895 8123 8198 8395 8549 8677 8618 8709 8938 9032 9115
104 131 123 110 104 104 115 145 134 117 117 117 117 117 117 117 116 117
92 106 105 89 88 87 92 117 113 91 95 90 87 93 99 100 92 97
Response rate % (n)c 75.0 71.7 77.1 69.7 65.9 74.7 60.9 66.7 67.3 74.7 72.6 70.0 66.7 57.0 53.5 55.0 46.7 61.9
(69) (76) (81) (62) (58) (65) (56) (78) (76) (68) (69) (63) (58) (53) (53) (55) (43) (60)
Table 2. Characteristics of dermatologists and their practices for survey years, NAMCS 2005–2010.
Number of visit records 1825 2065 1886 2043 1426 1525 1488 1989 1942 1723 1800 1499 1368 1309 1496 1523 1137 1510
a
Number of dermatologists in American Medical Association and American Osteopathic Association master files. Number of sampled dermatologists that met inclusion criteria. c Proportion of in-scope sample that participated. b
Based on data collected on dermatologists and their practices, 95% held MD degrees, and 93% practiced in private solo or group practice. The vast majority of practices received less than 25% of revenue from Medicaid, patient payment, or other sources. The largest proportion of revenue came from Medicare and private insurance. In 37% of responses, a census field representative completed the visit records for NAMCS, whereas 16.6% were completed by physicians (Table 2). In the evaluation of dermatology patient visit characteristics, there was slight predominance of female patients (57.5%), and the largest proportions of patients were reported as non-Hispanic/ Latino (79.2%) and white (84.8%). The main expected payment types were private insurance (61.6%) and Medicare (24.2%). Based on patients’ zip code, the largest proportion of patients lived in areas with less than 20% poverty, median incomes greater than $52 000, and areas with the highest percent of adults with Bachelor’s degree or higher (Table 3). Comparison to the dermatology practice profile survey In 2009, the response rate for the DPPS was 29% (n ¼ 1145), which is much lower than the response rates of dermatologists in the NAMCS. When NAMCS data on dermatologists were compared to DPPS data, there was concordance observed between the geographic distributions of dermatologists surveyed and the types of practice settings in which they worked. According to both surveys, one-third of dermatologists practiced in the southern region of the United States, which also represents the largest concentration of dermatologists by region (Table 4). Dermatologists in private solo and private group practices each made up 40–45% of surveyed dermatologists (Table 2). In reimbursements and revenue, the largest proportion of total revenue was from Medicare and private insurance (Table 4). In the remainder of NAMCS data on visit characteristics, there were no comparable data collected by the DPPS that reported on patient demographic information, median income, education level, and poverty level in the patient’s zip code. Although the DPPS did not report on the frequency that dermatologic procedures were performed, survey respondents reported on the types of procedures that they perform and almost all
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Geographic region Northeast Midwest South West MSAa Medical degree (MD vs. DO) Type of office setting Private solo practice Private group practice HMO or other prepaid practice Free standing clinic/urgicenter Non-Federal government clinic Federally qualified health center Employment status of physician Owner Employee Contractor Blank During past week, made any: (yes) Home visits Hospital visits Telephone consults E-mail consult Electronic medical record All electronic Part paper, part electronic All paper Blank Submit claims electronically Yes No Unknown/Blank % of revenue from medicare 525% 25–50% 51–75% 475% Unknown/blank % of revenue from medicaid 525% 25–50% 51–75% 475% Unknown/blank % of revenue from private insurance 525% 25–50% 51–75% 475% Unknown/blank % of revenue from patient payment 525% 25–50% 51–75% 475% Unknown/blank % of revenue other source 525% 25–50% 51–75% 475% Unknown/blank Number of managed care contracts 0 53 3–10
Unweighted records (n ¼ 297)
Estimated percent of physicians
60 72 94 71 277 289
21.2 20.5 34.5 23.9 93.7 95.0
137 138 13 7 1 1
48.2 44.8 4.3 2.4 0.2 0.1
228 54 14 1
77.9 17.2 4.5 0.5
7 71 142 36
2.2 24.8 50.2 12.7
60 28 207 2
18.8 8.8 71.4 1
193 71 33
63.3 25.5 11.2
108 137 28 9 15
37.3 44.7 8.7 3.9 5.4
277 4 0 0 15
93.2 1.0 – – 5.8
58 101 95 27 16
19.9 32.1 32.8 9.6 5.6
196 23 7 7 14
78.2 9.9 3.4 2.6 5.9
270 5 1 1 20
91.1 1.4 0.2 0.3 7.0
36 36 114
13.0 13.4 37.1 (continued )
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Table 3. Dermatology visit characteristics, NAMCS data.
Table 2. Continued
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Unweighted Estimated percent of records physicians (n ¼ 297) 410 Unknown/blank Accepting new patients Yes No Unknown/blank For new patients, accept the following: Capitate private insurance Non-capitate private insurance Medicare Medicaid Workers compensation Self-pay No charge Who completes the visit records for NAMCS Physician Office staff Census field representative Other Multiple categories checked Unknown/Blank
101 10
34.5 2
279 14 4
94.0 4.5 1.5
129 209 258 134 112 262 140
43.6 69.9 86.5 41.7 34.0 88.3 48.7
44 90 116 8 32 7
16.6 28.8 37.0 3.2 11.7 2.7
a
Metropolitan Statistical Area.
dermatologists performed simple excisions (92.6%), which were the most common procedure reported by NAMCS data (20.6% of all procedures, Table 5).
Discussion With tens of thousands of visits to dermatologists sampled (and many more skin disease visits to non-dermatologists), the NAMCS is a unique resource to evaluate outpatient dermatologic health care delivery in the US, providing a large representative sample of outpatient practice. Many important studies relevant to the outpatient practice of medicine have been published using this database, particularly in dermatology, a specialty that is largely practiced in the outpatient setting. While the detailed methodology of the NAMCS and all its benefits and limitations cannot typically be presented in those studies, this article attempts to clarify the study design, its advantages and limitations. Advantages of the NAMCS are the large size of the population of dermatologists and patient visits that are surveyed and the representativeness of this sample. Compared to primary care specialties, the NAMCS samples approximately twice the fraction of physicians in smaller specialties, such as dermatology. This deliberate oversampling provides a better opportunity to investigate patient care in these smaller specialties. The representativeness of dermatologists sampled by NAMCS is supported by the comparison of dermatologists characterized by the AAD’s DPPS. Furthermore, the NAMCS survey achieves annual response rates that are much higher than those achieved by other surveys conducted within dermatology. In large surveys conducted across national organizations including the AAD, the National Psoriasis Foundation (NPF), and the American Contact Dermatitis Society (ACDS), studies have achieved response rates between 36 and 39%.(6,7) The higher response rate in the NAMCS offers less potential for response bias and less potential for population bias which may occur in other survey studies due to sampling of dermatologists with pre-existing interests based on membership to particular societies. In a PubMed literature search, dermatology was among the top five research fields that used NAMCS data to report on
Sex – Female Race White Black Othera Blank, missing Race – imputed White Black Other Ethnicity Hispanic/Latino Non-Hispanic/Latino Unknown/Blank Expected main payment typeb Private insurance Medicare Medicaid or CHIP/SCHIP Worker’s compensation Self-pay No charge/charity Other Unknown/Blank Patient has been seen before graphical region Northeast Midwest South West Percent poverty in patient zip codec 55% 5–9.99% 10–19.99% 20þ% Unknown/Blank Median household income in patient’s zip codec Quartile 1 ($32,793 or less) Quartile 2 ($32,794–$40,626) Quartile 3 ($40,627–$52,387) Quartile 4 ($52,388 or more) Unknown/Blank % of adults with Bachelor’s degree or higher in patient’s zip codec Quartile 1 (512.84%) Quartile 2 (12.84–19.66%) Quartile 3 (19.67–31.68%) Quartile 4 (31.69þ%) Unknown/Blank Urban–rural classification of patient’s zip codec Large central metro Large fringe metro Medium metro Small metro Non-metro (micropolitan and non-core) Unknown/Blank
Unweighted records (n ¼ 29 554)
Estimated percent of visits
16 998
57.5
25 468 1330 964 1792
84.8 4.7 3.2 7.4
27 069 1438 1047
91.4 5.1 3.5
1264 23 988 4302
3.8 79.2 17.0
13 159 5265 419 23 1639 99 317 814 22 491
61.6 24.2 2.0 0.1 6.7 0.4 1.4 3.6 76.8
6015 6018 9343 8178
22.4 20.2 34.0 23.3
2183 2175 1781 463 418
28.4 31.7 27.5 6.9 5.5
868 1174 1736 2779 418
14.1 18.0 25.5 36.9 5.5
840 1182 1488 3047 418
13.9 18.7 22.0 40.0 5.5
2161 1777 1561 393 832
28.1 26.5 23.5 5.5 13.2
251
3.2
a
Including Asian, Native Hawaiian or other Pacific Islander, American Indian or Alaska Native, and more than one race reported. b Data collected from 1997 to 2010. c Data collected from 2006 to 2010.
outpatient care. Studies reporting on outpatient dermatologic care have examined the utilization of dermatologists and other physicians for skin-related complaints, as well as the management of specific dermatologic diseases, and patterns of use of
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Table 4. Comparison of data collected by the NAMCS and the American Academy of Dermatology Association (AADA).
Years studied Annual sample size Response rate Geographic region
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Work setting
Type of community served
NAMCS
DPPS
2005–2010 118 66%
2009 3999 29%
Northeast Midwest South West
21.2% 20.5% 34.5% 23.9%
Private solo Private group HMO or other prepaid practice
48.2% 44.8% 4.3%
Free standing clinic Non-Federal government clinic Federally qualified health center
2.4% 0.2% 0.1%
Large central metro Large fringe metro Medium metro Small metro Non-metro (micropolitan and non-core) Unknown/Blank
28.1% 26.5% 23.5% 5.5% 13.2% 3.2%
Midwest Northeastern Pacific Rocky Mountain Southern Other Solo Derm Group w/2 derms Derm Group w/3–5 derms Derm Group w/6 or more derms Multispecialty Group Academic Veterans Administration Military Other NR Urban Suburban Rural
18.8% 26.4% 15.0% 6.8% 32.3% 0.7% 39.% 16.7% 16.3% 7.6% 8.9% 8.0% 0.6% 0.9% 0.9% 0.6% 35% 54.1% 10%
Table 5. Leading diagnoses and procedures at dermatology visits, NAMCS data 1993–2010.
Leading diagnoses (ICD-9CM) Other acne (706.1) Actinic keratosis (702.0) Contact dermatitis and other eczema, unspecified cause (692.9) Benign neoplasm of skin (216.9) Other and unspecified malignant neoplasm of skin (173.9) Other seborrheic keratosis (702.19) Other psoriasis (696.1) Rosacea (695.3) Sebaceous cyst (706.2) Seborrheic dermatitis (690.1) Leading Procedures (ICD-9CM) Other local excision or destruction of lesion or tissue of skin and subcutaneous tissue (V86.30) Other anatomic and physiologic measurements and manual examinations (V89.39) Biopsy of skin and subcutaneous tissue (V86.11) Counseling (V94.49) Microscopic examination of specimen from skin and other integument (V91.69) Chemosurgery of skin (V86.24) Removal of other therapeutic device (V97.89) Other incision with drainage of skin and subcutaneous tissue (V86.04)
Unweighted records (n ¼ 29 554)
Percent of visits
4457 4430 2482 2349 1949 1800 1207 1109 1049 634
15.0 14.6 8.3 8.1 6.4 6.5 4.3 3.9 3.5 2.3
5626 4183 1801 464 382 243 224 126
20.9 13.4 6.5 1.6 1.3 0.9 0.8 0.4
ICD-9CM – International Classification of Diseases, 9th Revision, Clinical Modifications.
medications (8–15). Identifying physicians’ reported medical practices have aided in establishing community standards of care for common skin conditions (16). For example, some Medicare carriers considered requiring treatment of actinic keratosis with 5-fluorouracil before destruction in order to qualify for reimbursement in the 1990s. Data from NAMCS observed no uses of 5-fluorouaracil alone at first visits for actinic keratoses, indicating that the initial use of 5-fluorouracil was not a standard of care for treatment of these lesions among the medical community (15). Data from NAMCS has also been used to determine and compare costs of care for dermatologic diseases such as psoriasis (17).
Limitations and things to consider when interpreting NAMCS data A limitation of the NAMCS is that it samples ambulatory medical care, and inpatient hospital care and hospital-based outpatient care is not within the scope of the survey (other resources are available to study those populations). This is a significant limitation in other areas of medicine moreso than for dermatology, a specialty that largely takes place in the outpatient setting. As the NAMCS takes only a cross-section of visits to physicians’ offices, patients cannot be followed longitudinally to determine how their health changes over time. This limitation is apparent in
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the comparison of data from NAMCS and visit information based on Centricity EMRs databases, which found that NAMCS data was less sensitive in capturing chronic diagnoses, due to its focus on the primary presenting diagnosis of the office visit sampled. However, this finding is more likely to be significant in the setting of primary care office visits, where multiple chronic diagnoses may be present in one patient but only one may be the diagnosis related to the office visit. Moreover, while there is extensive information on treatment that can be used to identify practice gaps, there is no direct information in the NAMCS on the outcomes of treatment that would provide a direct measure of the impact of those gaps. No disease severity measures are recorded, therefore studies focused on outcomes must rely on other sources of data. NAMCS is also limited by the use of ICD-9CM codes for capturing procedure information. This system is not as granular as the Current Procedural Terminology (CPT) codes that dermatologists are familiar with and use in clinical practice. In addition, as the unit of sampling is a patient visit, disease prevalence cannot be directly determined, though health care utilization, as determined by visit rates per capita, can be reported. For each physician, a systematic sample of 1 weeks-worth of visits is taken, ranging from each visit sampled to one in five visits sampled. As sampling is not exhaustive, representative information on rarer conditions may not be available. As such, the data gives good representation of common diagnoses, procedures, and demographics, but may be underpowered for analyses of rare conditions, such as autoimmune blistering disorders. The NCHS, which administers the NAMCS, advises that all estimates based on fewer than 30 records or estimates with a standard error 30% of the estimate are considered unreliable and should not be reported. If a researcher is investigating multiple years of data individually, estimates from multiple years can be combined to increase sample size and improve reliability. While the validity of data on procedures and examinations from the NAMCS has been demonstrated in a direct observation of outpatient visits, caution is recommended when using the NAMCS for variables such as health behavior counseling and duration of office visits (2). Case reports and single-center studies are widely accepted in dermatology research and practice, despite their small sample sizes or lack of generalizability. The NAMCS provides researchers with a large, representative sample of outpatient office visits from across the United States that has the power to address many important questions about the delivery of dermatologic health care. While every clinical question requires a certain sample size that is dependent on the characteristics of the particular question, studying combined data over years of data from the NAMCS provides large enough samples to study some of the less common clinical problems and many of the common ones. Despite the limitations inherent to retrospective and survey-based data, the NAMCS is, in a time of changing health care delivery systems, an especially valuable tool for understanding how physicians and other health care providers care for patients with skin disease.
Declaration of interest The Center for Dermatology Research is supported by an unrestricted educational grant from Galderma Laboratories, L. P. Dr. Feldman is a
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consultant and speaker for Galderma, Stiefel/GlaxoSmithKline, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec, and Bristol Myers Squibb. Dr. Feldman has received grants from Galderma, Astellas, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec, Coria/Valeant, Pharmaderm, Ortho Pharmaceuticals, Aventis Pharmaceuticals, Roche Dermatology, 3M, Bristol Myers Squibb, Stiefel/GlaxoSmithKline, Novartis, Medicis, Leo, HanAll Pharmaceuticals, Celgene, Basilea, and Anacor and has received stock options from Photomedex. Dr. Fleischer has received support for research, speaking, or consulting from Astellas, Centocor, Amgen, Abbott, Galderma, Stiefel, Medicis, and Intendis, and is employed by Merz Pharmaceuticals. C. A., M. A., S. D., and K. H. have no conflicts to disclose.
References 1. Dermatology practice profile. Am Acad Dermatol. 2013;5:1. 2. Gilchrist VJ, Stange KC, Flocke SA, et al. A comparison of the National Ambulatory Medical Care Survey (NAMCS) measurement approach with direct observation of outpatient visits. Med Care. 2004;42:276–80. 3. Crawford AG, Cote C, Couto J, et al. Comparison of GE centricity electronic medical record database and national ambulatory medical care survey findings on the prevalence of major conditions in the United States. Popul Health Manag. 2010;13:139–50. 4. Cerner Multum. Available from http://www.multum.com/. Accessed August 4, 2013. 5. Ambulatory Health Care Data. Centers for Disease Control and Prevention. Available from http://www.cdc.gov/nchs/ahcd.htm. Accessed January 25, 2013 [February 27, 2013]. 6. Abuabara K, Wan J, Troxel AB, et al. Variation in dermatologist beliefs about the safety and effectiveness of treatments for moderate to severe psoriasis. J Am Acad Dermatol. 2013;68:262–9. 7. Nezafati KA, Carroll B, Storrs FJ, Cruz Jr PD. Making contact for contact dermatitis: a survey of the membership of the American Contact Dermatitis Society. Dermatitis. 2013;24:47–9. 8. Stern RS, Johnson ML, DeLozier J. Utilization of physician services for dermatologic complaints. The United States, 1974. Arch Dermatol. 1977;113:1062–6. 9. Fleischer Jr AB, Feldman SR, Bradham DD. Office-based physician services provided by dermatologists in the United States in 1990. J Invest Dermatol. 1994;102:93–7. 10. Nelson C. Office visits to dermatologists: National Ambulatory Medical Care Survey, United States, 1989–90. Adv Data. 1994;240: 1–12. 11. Krowchuk DP, Bradham DD, Fleischer Jr AB. Dermatologic services provided to children and adolescents by primary care and other physicians in the United States. Pediatr Dermatol. 1994;11: 199–203. 12. Kinney MA, Yentzer BA, Fleischer Jr AB, Feldman SR. Trends in the treatment of acne vulgaris: are measures being taken to avoid antimicrobial resistance? J Drugs Dermatol. 2010;9:519–24. 13. Stern RS. The pattern of topical corticosteroid prescribing in the United States, 1989–1991. J Am Acad Dermatol. 1996b;35:183–6. 14. Thevarajah S, Balkrishnan R, Camacho FT, et al. Trends in prescription of acne medication in the US: shift from antibiotic to non-antibiotic treatment. J Dermatolog Treat. 2005;16:224–8. 15. Feldman SR, Fleischer Jr AB, Williford PM, Jorizzo JL. Destructive procedures are the standard of care for treatment of actinic keratoses. J Am Acad Dermatol. 1999;40:43–7. 16. de BD, McGregor JM, Hughes BR. Guidelines for the management of actinic keratoses. Br J Dermatol. 2007;156:222–30. 17. Javitz HS, Ward MM, Farber E, et al. The direct cost of care for psoriasis and psoriatic arthritis in the United States. J Am Acad Dermatol. 2002;46:850–60.
EDITORIAL
The National Ambulatory Medical Care Survey: A resource for understanding the outpatient dermatology treatment Christine S. Ahn1, Mary-Margaret Allen1, Scott A. Davis1, Karen E. Huang1, Alan B. Fleischer Jr.1, and Steven R. Feldman1,2,3 Department of Dermatology and 2Department of Pathology, and 3Department of Public Health Sciences, Center for Dermatology Research, Wake Forest School of Medicine, Winston-Salem, NC, USA Abstract
Keywords
Background: The National Ambulatory Care Survey (NAMCS) collects information on outpatient medical care in the United States. Key characteristics of the NAMCS methodology are not well recognized. We describe the NAMCS survey design and patient visits to dermatologists and to present information on the validity of the NAMCS data by comparing key features of the dermatologist sample to other surveys of dermatologists. Methods: NAMCS data on dermatologists and skin-related visits from 1993 to 2010 were analyzed and compared to the Dermatology Physician Profile Survey (DPPS), a survey by the American Academy of Dermatology. Results: A total of 29 554 patient visits to dermatologists were sampled from 1993 to 2010. On average, 118 dermatologists were sampled annually to participate in the NAMCS, and response rates ranged from 47 to 77%. The NAMCS and the DPPS found similar dermatologist demographics, practice settings and reimbursement sources. Conclusion: Overall, the NAMCS achieves high-response rates and provides a generalizable sample that has been used in scores of studies of dermatology outpatient treatment. In a time of changing health care delivery systems, NAMCS is valuable for understanding how physicians care for patients with skin disease.
AAD, cutaneous, dermatologist, DPPS, NAMCS, skin
Introduction The practice of dermatology presents innumerable important clinical questions. Many of these questions are difficult or impossible to answer with prospective studies. Moreover, clinical trials do not answer questions about how medicine is actually practiced in the community. Retrospective studies have an important place in addressing many clinical issues. The strengths of retrospective designs include the relatively inexpensive cost, ability to analyze multiple outcomes, and the ability to analyze low-incidence diseases. These strengths can be used to answer a wide range of research questions, including critically important issues on what diseases are being treated and how the practice of dermatology is changing. The National Ambulatory Medical Care Survey (NAMCS) is a large, nationally representative survey of U.S. outpatient medical practice that has been used extensively to address questions involving the management of patients with skin disease. Previous studies that have used data from NAMCS do not provide extensive detail on the methodology of this survey; the accuracy of studies using the NAMCS depends on the representativeness of the sample of dermatologists who provide data.
Correspondence: Steven R. Feldman, MD, PhD, Department of Dermatology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. Tel: 336 716 7740. Fax: 336 716 7732. E-mail: [email protected]
History Accepted 21 October 2013 Published online 20 November 2013
The purpose of this study was to describe the NAMCS survey design, to describe patient visit characteristics to dermatologists by NAMCS data from 2005 to 2010, to validate the NAMCS by comparing characteristics of dermatologists surveyed in NAMCS from 2005 to 2010 to dermatologists surveyed in the Dermatology Physician Profile Survey (DPPS).
Methods NAMCS survey design
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The methodology of the NAMCS surveys was reviewed based on a methods template produced by the National Hospital Ambulatory Medical Care Survey (NHAMCS) staff that is recommended to be included in all NHAMCS publication. This was adapted to the methodology of NAMCS. Dermatologist and patient visit characteristics Data from the National Ambulatory Care Survey were analyzed from 1993 to 2010 to determine the sample sizes and response rates among dermatologists. To determine specific physician characteristics, data from 2005 to 2010 were analyzed, when the physician statistical weight was made available. The physician characteristics recorded by NAMCS include the type of doctor (MD or DO); employment status; and whether any home visits, hospital visits, or consults over the phone or e-mail were conducted within the previous week. Office-based information collected includes U.S. geographic location of the office; the
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metropolitan statistical area of the office; type of office; practice ownership; electronic medical record (EMR) usage; submission of claims electronically; percent of revenue from Medicare, Medicaid, private insurance, or other source; the number of managed care contracts; status of accepting new patients and if so, the types of payments accepted from these patients – capitated payment, non-capitated payment, Medicare, Medicaid, private insurance, worker’s compensation, self-pay, or no charge. For visit records, patient demographic information including age, sex, ethnicity, and race (un-imputed and imputed for missing responses) is recorded. In addition, the expected main type of payment (since 1997), whether the patient was new to the practice, and U.S. geographic location of the visit (Northeast, Midwest, South, West) are documented. Starting in 2006, data were collected to roughly indicate the socioeconomic status of patients seen by a physician. For each patient’s home zip code, the percent of people in poverty, median household income, percent of adults with a Bachelor’s degree, and urban/rural classification were identified. Comparison to the dermatology practice profile survey To evaluate the generalizability of NAMCS data on dermatologic services in the US, physician and outpatient visit characteristics of dermatologists reported by the NAMCS survey were compared to the results of the dermatology practice profile survey (DPPS) published by the American Academy of Dermatology (AAD). The DPPS, which is a national survey of practicing members of the AAD, surveys a stratified random sample of associates, life, and honorary Academy members. Members are excluded if they were international members, known retirees, and those older than 72 years. This survey, which was first administered in 2002, has been conducted every other year and collects information on the characteristics of dermatology practice, including practice activities, quality measures and systems, reimbursement sources, and insurance. Beginning in 2007, the survey also included sections pertaining to the use of physician assistants and nurse practitioners in dermatology practice (1). The results of the NAMCS from 2005 to 2010 were compared to results of the 2009 DPPS.
Results NAMCS survey design The NAMCS has been conducted annually since 1989 by the Center for Disease Control and Prevention’s National Center for Health Statistics (NCHS) branch. The survey samples outpatient visits to physicians and are defined as working ‘‘office-based’’ by the American Medical Association (AMA) or American Osteopathic Association (AOA). Federally administered practices (such as an outpatient military or Veterans Administration facility) are not included. The sample is selected using a threestage process: (i) 112 geographic areas (counties, townships, or equivalents of these areas) in the 50 states and District of Columbia are sampled; (ii) practicing physicians are sampled from master files maintained by the AMA and AOA after stratifying the lists by 15 physician specialties, including dermatology; (iii) for each physician, an approximately 1-week period from the year is randomly sampled, from which a portion of visits are systematically chosen. Sampling rates of visits during that week range from 20% for busy practices to 100% for less busy practices, producing around 20–30 visits for each office surveyed in a given year. Types of patient–physician contacts that are not included are consults over the phone, visits at institutions where the institution has primary responsibility for the patient, visits for administrative purposes, house-calls, or visits at a hospital. For each visit sampled, the physician, the physician’s staff, or a Census Bureau representative fill out a form based on medical
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records. Data collected include patient demographics, type of payer, reason for visit (from the patient’s perspective), diagnoses given at the visit (up to three), medications newly prescribed or continued, procedures performed, visit characteristics (i.e. counseling offered, screening tests given, time spent with the physician, and use of a physician extender at the visit), and office characteristics (i.e. use of EMRs, amount of revenue from different sources, and acceptance of new patients). Previous studies have examined the accuracy of the information recorded by the NAMCS by comparing the NAMCS measurement approach with other measures, including direct observation of outpatient visits and Centricity EMR databases (2,3). When NAMCS findings were compared to visit content measured by direct observation, the NAMCS physician report method was more accurate for reporting procedures and examinations. However, the NAMCS under-reported behavioral counseling (such as alcohol counseling and smoking cessation advice) and over-reported visit duration (2). In the comparison of NAMCS findings to Centricity EMR databases, the EMR data showed higher proportions of visits by younger patients and by females than data from the NAMCS, and demonstrated a higher sensitivity in capturing chronic diagnoses. This observation was thought to be due to the medical documentation requirements for the Centricity EMR, such as inclusion of laboratory results and medication information, in contrast to the NAMCS, which focuses on the primary reason for the office visit (3). Over the years, some survey items have been added, removed or modified, so care needs to be taken when combining multiple years of data together. Records are then processed by an independent center that classifies diagnoses, causes of injury, and procedures by the International Classification of Disease, 9th Revision, Clinical Modification (ICD-9CM) codes and reasons for visits using the Reason for Visit Classification for Ambulatory Care. Up until 2006, the Federal National Drug codes were used to classify medications; from 2006 and later, Multum’s Lexicon Drug database was used for medication classification (4). NCHS provides sample SAS code so that data users can modify medication classifications prior to 2006 to match the Multum’s Lexicon Drug database classification. The NAMCS data are de-identified and made freely available to researchers on the NCHS website in SAS, SUDAN, SPSS, and Stata format (5). In addition, tutorials are available on the website for researchers using the data. From 1993 and forward, masked patient visit weights and survey design items were made available so that researchers can produce accurate, unbiased national estimates. Survey visit weights correct for non-response rates after taking into account when (time of year) and where (geographic location and urbanization) visits were sampled. Starting in 2005, physician weights were also made available for physician-level analyses (this permits studies to answer questions such as ‘‘what percentage of dermatologists use an electronic medical record system?’’). Data can be combined with U.S. Census data to assess the number of visits per 100 000 population of a specific demographic, or with data on the number of licensed physicians to assess the average caseload within particular specialties. Dermatology visit characteristics On average, from 7931 dermatologists on the AMA and AOA physician master lists, 118 dermatologists were sampled each year, with 18% of those sampled not meeting eligibility criteria. The most common reasons for non-eligibility were physicians working in a hospital outpatient department, working in an institutional setting and being retired. Of those sampled that were eligible, 66% participated in the survey process (varying from 46.7% in 2009 to 77.1% in 1995). A total of 29 554 patient-visits to dermatologists were sampled and recorded from 1993 to 2010 (ranging from 1137 in 2009 to 2065 in 1994, Table 1).
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Table 1. Sampling and response rates of dermatologists for NAMCS survey, 1993–2010.
Year
Sampling poola
Total sampled
In-scopeb
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
6447 6445 6813 6900 7152 7572 7172 7895 8123 8198 8395 8549 8677 8618 8709 8938 9032 9115
104 131 123 110 104 104 115 145 134 117 117 117 117 117 117 117 116 117
92 106 105 89 88 87 92 117 113 91 95 90 87 93 99 100 92 97
Response rate % (n)c 75.0 71.7 77.1 69.7 65.9 74.7 60.9 66.7 67.3 74.7 72.6 70.0 66.7 57.0 53.5 55.0 46.7 61.9
(69) (76) (81) (62) (58) (65) (56) (78) (76) (68) (69) (63) (58) (53) (53) (55) (43) (60)
Table 2. Characteristics of dermatologists and their practices for survey years, NAMCS 2005–2010.
Number of visit records 1825 2065 1886 2043 1426 1525 1488 1989 1942 1723 1800 1499 1368 1309 1496 1523 1137 1510
a
Number of dermatologists in American Medical Association and American Osteopathic Association master files. Number of sampled dermatologists that met inclusion criteria. c Proportion of in-scope sample that participated. b
Based on data collected on dermatologists and their practices, 95% held MD degrees, and 93% practiced in private solo or group practice. The vast majority of practices received less than 25% of revenue from Medicaid, patient payment, or other sources. The largest proportion of revenue came from Medicare and private insurance. In 37% of responses, a census field representative completed the visit records for NAMCS, whereas 16.6% were completed by physicians (Table 2). In the evaluation of dermatology patient visit characteristics, there was slight predominance of female patients (57.5%), and the largest proportions of patients were reported as non-Hispanic/ Latino (79.2%) and white (84.8%). The main expected payment types were private insurance (61.6%) and Medicare (24.2%). Based on patients’ zip code, the largest proportion of patients lived in areas with less than 20% poverty, median incomes greater than $52 000, and areas with the highest percent of adults with Bachelor’s degree or higher (Table 3). Comparison to the dermatology practice profile survey In 2009, the response rate for the DPPS was 29% (n ¼ 1145), which is much lower than the response rates of dermatologists in the NAMCS. When NAMCS data on dermatologists were compared to DPPS data, there was concordance observed between the geographic distributions of dermatologists surveyed and the types of practice settings in which they worked. According to both surveys, one-third of dermatologists practiced in the southern region of the United States, which also represents the largest concentration of dermatologists by region (Table 4). Dermatologists in private solo and private group practices each made up 40–45% of surveyed dermatologists (Table 2). In reimbursements and revenue, the largest proportion of total revenue was from Medicare and private insurance (Table 4). In the remainder of NAMCS data on visit characteristics, there were no comparable data collected by the DPPS that reported on patient demographic information, median income, education level, and poverty level in the patient’s zip code. Although the DPPS did not report on the frequency that dermatologic procedures were performed, survey respondents reported on the types of procedures that they perform and almost all
455
Geographic region Northeast Midwest South West MSAa Medical degree (MD vs. DO) Type of office setting Private solo practice Private group practice HMO or other prepaid practice Free standing clinic/urgicenter Non-Federal government clinic Federally qualified health center Employment status of physician Owner Employee Contractor Blank During past week, made any: (yes) Home visits Hospital visits Telephone consults E-mail consult Electronic medical record All electronic Part paper, part electronic All paper Blank Submit claims electronically Yes No Unknown/Blank % of revenue from medicare 525% 25–50% 51–75% 475% Unknown/blank % of revenue from medicaid 525% 25–50% 51–75% 475% Unknown/blank % of revenue from private insurance 525% 25–50% 51–75% 475% Unknown/blank % of revenue from patient payment 525% 25–50% 51–75% 475% Unknown/blank % of revenue other source 525% 25–50% 51–75% 475% Unknown/blank Number of managed care contracts 0 53 3–10
Unweighted records (n ¼ 297)
Estimated percent of physicians
60 72 94 71 277 289
21.2 20.5 34.5 23.9 93.7 95.0
137 138 13 7 1 1
48.2 44.8 4.3 2.4 0.2 0.1
228 54 14 1
77.9 17.2 4.5 0.5
7 71 142 36
2.2 24.8 50.2 12.7
60 28 207 2
18.8 8.8 71.4 1
193 71 33
63.3 25.5 11.2
108 137 28 9 15
37.3 44.7 8.7 3.9 5.4
277 4 0 0 15
93.2 1.0 – – 5.8
58 101 95 27 16
19.9 32.1 32.8 9.6 5.6
196 23 7 7 14
78.2 9.9 3.4 2.6 5.9
270 5 1 1 20
91.1 1.4 0.2 0.3 7.0
36 36 114
13.0 13.4 37.1 (continued )
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Table 3. Dermatology visit characteristics, NAMCS data.
Table 2. Continued
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Unweighted Estimated percent of records physicians (n ¼ 297) 410 Unknown/blank Accepting new patients Yes No Unknown/blank For new patients, accept the following: Capitate private insurance Non-capitate private insurance Medicare Medicaid Workers compensation Self-pay No charge Who completes the visit records for NAMCS Physician Office staff Census field representative Other Multiple categories checked Unknown/Blank
101 10
34.5 2
279 14 4
94.0 4.5 1.5
129 209 258 134 112 262 140
43.6 69.9 86.5 41.7 34.0 88.3 48.7
44 90 116 8 32 7
16.6 28.8 37.0 3.2 11.7 2.7
a
Metropolitan Statistical Area.
dermatologists performed simple excisions (92.6%), which were the most common procedure reported by NAMCS data (20.6% of all procedures, Table 5).
Discussion With tens of thousands of visits to dermatologists sampled (and many more skin disease visits to non-dermatologists), the NAMCS is a unique resource to evaluate outpatient dermatologic health care delivery in the US, providing a large representative sample of outpatient practice. Many important studies relevant to the outpatient practice of medicine have been published using this database, particularly in dermatology, a specialty that is largely practiced in the outpatient setting. While the detailed methodology of the NAMCS and all its benefits and limitations cannot typically be presented in those studies, this article attempts to clarify the study design, its advantages and limitations. Advantages of the NAMCS are the large size of the population of dermatologists and patient visits that are surveyed and the representativeness of this sample. Compared to primary care specialties, the NAMCS samples approximately twice the fraction of physicians in smaller specialties, such as dermatology. This deliberate oversampling provides a better opportunity to investigate patient care in these smaller specialties. The representativeness of dermatologists sampled by NAMCS is supported by the comparison of dermatologists characterized by the AAD’s DPPS. Furthermore, the NAMCS survey achieves annual response rates that are much higher than those achieved by other surveys conducted within dermatology. In large surveys conducted across national organizations including the AAD, the National Psoriasis Foundation (NPF), and the American Contact Dermatitis Society (ACDS), studies have achieved response rates between 36 and 39%.(6,7) The higher response rate in the NAMCS offers less potential for response bias and less potential for population bias which may occur in other survey studies due to sampling of dermatologists with pre-existing interests based on membership to particular societies. In a PubMed literature search, dermatology was among the top five research fields that used NAMCS data to report on
Sex – Female Race White Black Othera Blank, missing Race – imputed White Black Other Ethnicity Hispanic/Latino Non-Hispanic/Latino Unknown/Blank Expected main payment typeb Private insurance Medicare Medicaid or CHIP/SCHIP Worker’s compensation Self-pay No charge/charity Other Unknown/Blank Patient has been seen before graphical region Northeast Midwest South West Percent poverty in patient zip codec 55% 5–9.99% 10–19.99% 20þ% Unknown/Blank Median household income in patient’s zip codec Quartile 1 ($32,793 or less) Quartile 2 ($32,794–$40,626) Quartile 3 ($40,627–$52,387) Quartile 4 ($52,388 or more) Unknown/Blank % of adults with Bachelor’s degree or higher in patient’s zip codec Quartile 1 (512.84%) Quartile 2 (12.84–19.66%) Quartile 3 (19.67–31.68%) Quartile 4 (31.69þ%) Unknown/Blank Urban–rural classification of patient’s zip codec Large central metro Large fringe metro Medium metro Small metro Non-metro (micropolitan and non-core) Unknown/Blank
Unweighted records (n ¼ 29 554)
Estimated percent of visits
16 998
57.5
25 468 1330 964 1792
84.8 4.7 3.2 7.4
27 069 1438 1047
91.4 5.1 3.5
1264 23 988 4302
3.8 79.2 17.0
13 159 5265 419 23 1639 99 317 814 22 491
61.6 24.2 2.0 0.1 6.7 0.4 1.4 3.6 76.8
6015 6018 9343 8178
22.4 20.2 34.0 23.3
2183 2175 1781 463 418
28.4 31.7 27.5 6.9 5.5
868 1174 1736 2779 418
14.1 18.0 25.5 36.9 5.5
840 1182 1488 3047 418
13.9 18.7 22.0 40.0 5.5
2161 1777 1561 393 832
28.1 26.5 23.5 5.5 13.2
251
3.2
a
Including Asian, Native Hawaiian or other Pacific Islander, American Indian or Alaska Native, and more than one race reported. b Data collected from 1997 to 2010. c Data collected from 2006 to 2010.
outpatient care. Studies reporting on outpatient dermatologic care have examined the utilization of dermatologists and other physicians for skin-related complaints, as well as the management of specific dermatologic diseases, and patterns of use of
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Table 4. Comparison of data collected by the NAMCS and the American Academy of Dermatology Association (AADA).
Years studied Annual sample size Response rate Geographic region
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Work setting
Type of community served
NAMCS
DPPS
2005–2010 118 66%
2009 3999 29%
Northeast Midwest South West
21.2% 20.5% 34.5% 23.9%
Private solo Private group HMO or other prepaid practice
48.2% 44.8% 4.3%
Free standing clinic Non-Federal government clinic Federally qualified health center
2.4% 0.2% 0.1%
Large central metro Large fringe metro Medium metro Small metro Non-metro (micropolitan and non-core) Unknown/Blank
28.1% 26.5% 23.5% 5.5% 13.2% 3.2%
Midwest Northeastern Pacific Rocky Mountain Southern Other Solo Derm Group w/2 derms Derm Group w/3–5 derms Derm Group w/6 or more derms Multispecialty Group Academic Veterans Administration Military Other NR Urban Suburban Rural
18.8% 26.4% 15.0% 6.8% 32.3% 0.7% 39.% 16.7% 16.3% 7.6% 8.9% 8.0% 0.6% 0.9% 0.9% 0.6% 35% 54.1% 10%
Table 5. Leading diagnoses and procedures at dermatology visits, NAMCS data 1993–2010.
Leading diagnoses (ICD-9CM) Other acne (706.1) Actinic keratosis (702.0) Contact dermatitis and other eczema, unspecified cause (692.9) Benign neoplasm of skin (216.9) Other and unspecified malignant neoplasm of skin (173.9) Other seborrheic keratosis (702.19) Other psoriasis (696.1) Rosacea (695.3) Sebaceous cyst (706.2) Seborrheic dermatitis (690.1) Leading Procedures (ICD-9CM) Other local excision or destruction of lesion or tissue of skin and subcutaneous tissue (V86.30) Other anatomic and physiologic measurements and manual examinations (V89.39) Biopsy of skin and subcutaneous tissue (V86.11) Counseling (V94.49) Microscopic examination of specimen from skin and other integument (V91.69) Chemosurgery of skin (V86.24) Removal of other therapeutic device (V97.89) Other incision with drainage of skin and subcutaneous tissue (V86.04)
Unweighted records (n ¼ 29 554)
Percent of visits
4457 4430 2482 2349 1949 1800 1207 1109 1049 634
15.0 14.6 8.3 8.1 6.4 6.5 4.3 3.9 3.5 2.3
5626 4183 1801 464 382 243 224 126
20.9 13.4 6.5 1.6 1.3 0.9 0.8 0.4
ICD-9CM – International Classification of Diseases, 9th Revision, Clinical Modifications.
medications (8–15). Identifying physicians’ reported medical practices have aided in establishing community standards of care for common skin conditions (16). For example, some Medicare carriers considered requiring treatment of actinic keratosis with 5-fluorouracil before destruction in order to qualify for reimbursement in the 1990s. Data from NAMCS observed no uses of 5-fluorouaracil alone at first visits for actinic keratoses, indicating that the initial use of 5-fluorouracil was not a standard of care for treatment of these lesions among the medical community (15). Data from NAMCS has also been used to determine and compare costs of care for dermatologic diseases such as psoriasis (17).
Limitations and things to consider when interpreting NAMCS data A limitation of the NAMCS is that it samples ambulatory medical care, and inpatient hospital care and hospital-based outpatient care is not within the scope of the survey (other resources are available to study those populations). This is a significant limitation in other areas of medicine moreso than for dermatology, a specialty that largely takes place in the outpatient setting. As the NAMCS takes only a cross-section of visits to physicians’ offices, patients cannot be followed longitudinally to determine how their health changes over time. This limitation is apparent in
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the comparison of data from NAMCS and visit information based on Centricity EMRs databases, which found that NAMCS data was less sensitive in capturing chronic diagnoses, due to its focus on the primary presenting diagnosis of the office visit sampled. However, this finding is more likely to be significant in the setting of primary care office visits, where multiple chronic diagnoses may be present in one patient but only one may be the diagnosis related to the office visit. Moreover, while there is extensive information on treatment that can be used to identify practice gaps, there is no direct information in the NAMCS on the outcomes of treatment that would provide a direct measure of the impact of those gaps. No disease severity measures are recorded, therefore studies focused on outcomes must rely on other sources of data. NAMCS is also limited by the use of ICD-9CM codes for capturing procedure information. This system is not as granular as the Current Procedural Terminology (CPT) codes that dermatologists are familiar with and use in clinical practice. In addition, as the unit of sampling is a patient visit, disease prevalence cannot be directly determined, though health care utilization, as determined by visit rates per capita, can be reported. For each physician, a systematic sample of 1 weeks-worth of visits is taken, ranging from each visit sampled to one in five visits sampled. As sampling is not exhaustive, representative information on rarer conditions may not be available. As such, the data gives good representation of common diagnoses, procedures, and demographics, but may be underpowered for analyses of rare conditions, such as autoimmune blistering disorders. The NCHS, which administers the NAMCS, advises that all estimates based on fewer than 30 records or estimates with a standard error 30% of the estimate are considered unreliable and should not be reported. If a researcher is investigating multiple years of data individually, estimates from multiple years can be combined to increase sample size and improve reliability. While the validity of data on procedures and examinations from the NAMCS has been demonstrated in a direct observation of outpatient visits, caution is recommended when using the NAMCS for variables such as health behavior counseling and duration of office visits (2). Case reports and single-center studies are widely accepted in dermatology research and practice, despite their small sample sizes or lack of generalizability. The NAMCS provides researchers with a large, representative sample of outpatient office visits from across the United States that has the power to address many important questions about the delivery of dermatologic health care. While every clinical question requires a certain sample size that is dependent on the characteristics of the particular question, studying combined data over years of data from the NAMCS provides large enough samples to study some of the less common clinical problems and many of the common ones. Despite the limitations inherent to retrospective and survey-based data, the NAMCS is, in a time of changing health care delivery systems, an especially valuable tool for understanding how physicians and other health care providers care for patients with skin disease.
Declaration of interest The Center for Dermatology Research is supported by an unrestricted educational grant from Galderma Laboratories, L. P. Dr. Feldman is a
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consultant and speaker for Galderma, Stiefel/GlaxoSmithKline, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec, and Bristol Myers Squibb. Dr. Feldman has received grants from Galderma, Astellas, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec, Coria/Valeant, Pharmaderm, Ortho Pharmaceuticals, Aventis Pharmaceuticals, Roche Dermatology, 3M, Bristol Myers Squibb, Stiefel/GlaxoSmithKline, Novartis, Medicis, Leo, HanAll Pharmaceuticals, Celgene, Basilea, and Anacor and has received stock options from Photomedex. Dr. Fleischer has received support for research, speaking, or consulting from Astellas, Centocor, Amgen, Abbott, Galderma, Stiefel, Medicis, and Intendis, and is employed by Merz Pharmaceuticals. C. A., M. A., S. D., and K. H. have no conflicts to disclose.
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