The document summarizes the National Ambulatory Medical Care Survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS), which collect data on outpatient visits through annual probability samples. Key points include: 1) NAMCS collects data from office-based physicians while NHAMCS collects data from emergency and outpatient departments. 2) The surveys were established in the 1970s and track health care practices, conditions, priorities, and Healthy People objectives. 3) Data is used by medical groups, government agencies, researchers and media to inform policy, study prescribing rates, and more.

1. Linda McCaig and David Woodwell Ambulatory Care Statistics Branch Division of Health Care Statistics National Center for Health Statistics/CDC Using NAMCS and NHAMCS Data

2. Overview Background Data uses Survey methodology Current and proposed survey items User considerations Methodological studies Data dissemination NCHS Research Data Center

4. National probability sample surveys National Ambulatory Medical Care Survey (NAMCS) Patient visits to non-federal office-based physicians National Hospital Ambulatory Medical Care Survey (NHAMCS) Patient visits to EDs and OPDs of non-federal short-stay hospitals

5. Original NAMCS survey goals National statistics Professional education Health policy formulation Medical practice management Quality assurance

6. NAMCS history Survey began in 1973 Annual data collection through 1981 (NORC) Conducted in 1985 (NORC) Annual began again in 1989 (Census)

7. NHAMCS history Survey began in 1992 Annual data collection (Census)

8. How are NAMCS and NHAMCS data used?

9. Data uses To understand health care practice and find inequities To track certain conditions To establish national priorities To serve as comparison points for states To measure Healthy People objectives

10. Data users Over 100 journal publications in last 2 years Medical associations Government agencies Health services researchers University and medical schools Broadcast and print media

11. Setting government policy ED as a “safety net” for the uninsured Development of the Resource-Based Relative Value Scale (RBRVS)

13. Antibiotic prescribing rates at physician office visits for children Rate per 1000 population Rate per 1000 visits

15. Prescribing rates at physician office visits by specialty Psychiatry Ophthalmology Otolaryngology Orthopedic surgery

16. Female ambulatory care visit rates for selected diagnoses by race

17. Annual rate of illness and injury ED visits for seniors by race Illness, black 1 Illness, white 1 Injury, black 1 NOTE: 1 p < .01. Injury, white

18. Diabetes visit rates per 10,000 persons by setting 49 147 1289 1998-99 38 157 1118 1996-97 36 117 865 1994-95 33 84 962 1992-93 ED OPD Office Year

19. NAMCS and NHAMCS Methodology

20. NAMCS Scope Includes non-federal, office-based physicians Excludes physicians whose main activity is teaching, research, administration, hospital-based care, or who are unclassified as to activity and those in the certain specialties

21. In-Scope NAMCS locations Freestanding clinic/urgicenter Federally qualified health center Neighborhood and mental health centers Non-federal government clinic Family planning clinic Health maintenance organization Faculty practice plan Private solo or group practice

22. Out-of-Scope NAMCS locations Hospital ED’s and OPD’s Ambulatory surgicenter Institutional setting (schools, prisons) Industrial outpatient facility Federal Government operated clinic Laser vision surgery

23. NAMCS Sample design 112 NHIS PSUs 3,000 physicians 25,000 visits 1 week reporting period

24. NHAMCS Scope OPD was intended to be parallel to the NAMCS in the hospital setting General medicine, surgery, pediatrics, ob/gyn, substance abuse, and “other” clinics are in-scope Ancillary services are out of scope

25. NHAMCS Sample design 112 NHIS PSUs 500 hospitals 400 EDs and 250 OPDs 24,000 ED visits and 30,000 OPD visits 4-week reporting period

26. Gaining cooperation Advance letters Endorsement letters Public relations materials Conversion of refusal

27. Data collection procedures Induction visit by Census field representative (FR) FR training of office/hospital staff Random start number Take every number Prospective or retrospective method

28. Items collected Patient characteristics age, race, sex Visit characteristics Reason for visit, diagnosis, medication Provider characteristics physician specialty, hospital ownership

29. Repeating fields Reason for visit (3) Cause of injury (3) Diagnosis (3) Ambulatory surgical procedures (2) Medications (6)

30. Data processing Data are coded and keyed by Analytical Sciences Inc. (ASI) Quality control procedures Edit checks by NCHS

31. Coding systems used A Reason for Visit Classification (NCHS) ICD-9-CM Drug coding classification system (NCHS) National Drug Code Directory

32. NAMCS and NHAMCS 1999-2000 PRFs

33. Patient record form - common items Patient’s zip code Date of visit Date of birth Sex Ethnicity

34. Patient record form - common items Race Source of payment HMO status Reason for visit

35. Patient record form – common items Diagnosis Diagnostic/screening services Medications Providers seen Visit disposition

36. Injury items External cause – narrative text since 1997 Place of injury Work related injury Intent

37. Office and OPD PRF - unique items Was patient referred for visit Patient’s primary care physician Patient seen before Major reason for visit

38. Office and OPD PRF - unique items Ambulatory surgical procedures Therapeutic and preventive services Time spent with physician (NAMCS only)

39. ED Patient record form - unique items Arrival time Discharge time Immediacy Presenting level of pain Procedures

40. NAMCS and NHAMCS PRF revisions 2001-02 – emphasis on the continuity of care

41. Office and OPD PRF - new items for 2001-02 How many visits in last 12 months Initial or follow-up visit Do other physicians share care Total number of medications

42. ED PRF - new items for 2001-02 Discharge time Visit related to alcohol use Patient seen in last 72 hours Initial or follow-up visit Visit related to adverse drug event Initial vital signs Total number of medications

43. NAMCS and NHAMCS PRF revisions 2003-04

44. ED PRF- revisions for 2003-04 New oriented X 3 is visit work related list up to 8 medications Recycled mode of arrival presenting level of pain time seen by physician

45. 2001-02 Induction Interview revisions NAMCS – e.g., electronic medical records, number of managed care contracts NHAMCS – e.g., Pediatric Emergency Services and Equipment Supplement (HRSA)

46. 2003-04 Induction Interview revisions NAMCS – e.g., Physician was a member of a practice-based research network (PBRN) NHAMCS – e.g., Daily census of occupied and available beds

47. ED Overcrowding Physician coverage hours Log of ambulance diversion

48. Analysis of Facility Level Data

49. Percent of physicians who do not accept new patients by payment type

50. Distribution of hospital EDs on average waiting time

51. Overview User considerations Encounter vs. person data Sampling error Nonsampling error Methodological studies Data dissemination NCHS Research Data Center

52. Encounter vs. person data NAMCS and NHAMCS are record-based surveys Not population-based surveys (NHIS) Estimates are in terms of visits and not persons Can not calculate incidence or prevalence rates from our estimates

53. Sample weight Sample data MUST be weighted to produce national estimates Estimation process Adjusts for survey and item nonresponse Makes several ratio adjustments within and across physician specialties and hospitals

54. Sampling error NAMCS and NHAMCS are not simple random samples Clustering effects of visits within the physician’s practice and also physician practices within PSUs Must use generalized variance curve or SUDAAN to calculate SEs for all estimates, percents, and rates.

55. Reliability criteria Estimates based on at least 30 raw cases are reliable Estimates with a relative standard error (RSE) less than 30 percent are reliable Both conditions must be met

56. Ways to improve reliability of estimates Combine NAMCS, ED and OPD data to produce ambulatory care visit estimates Combine multiple years of data

57. Nonsampling error Frame coverage Reporting and processing errors Biases due to survey and item nonresponse Incomplete responses

58. Minimizing nonsampling error Improve sample frame for better coverage Encourage uniform reporting and eliminate ambiguities Pretest survey items and procedures Perform quality control procedures – consistency and edit checks Train Census field representatives

59. NAMCS Response rates

60. NHAMCS Response rates ED OPD

61. Attempts to improve response rate Publicity Eliminating questions that have a high item non-response Incentives test

62. Methodological studies Nonresponse study Complement study Motivational insert Form length Incentive test

63. Initial results of incentives test Still very early Participation in some “on the fence” cases No effect on “extreme” cases

64. Data dissemination

66. Outside research Journal articles List on Ambulatory Care web site Text books Department level publications Health US

67. Microdata files Downloadable files NAMCS, 1973-2000 NHAMCS, 1992-2000 CD-ROMs NAMCS, 1990-2000 NHAMCS, 1992-2000 Tapes/cartridges (NTIS) NAMCS, 1973-1997 NHAMCS, 1992-1997

68. Enhanced public-use files SAS variable labels, value labels, and format assignments (1997-2000) Sample design variables Allow use of SUDAAN and STATA 1997-2000 NAMCS and NHAMCS Files prior to 2000 have been updated on web site

69. Comparison of RSEs Physician assistant Seen by Cardiac monitor IV fluids Admitted to hosp 0 5 10 15 20 RSE In-house Masked GVC

70. Comparison of RSEs for ED visits by age Patient age in years In-house Public-use 1-stage gvc <15 15-24 25-44 45-64 65-74 75+ 0 5 10 15 RSE

71. Future release NAMCS Trend file 1980-81, 1985, 1990-91, 1995-96, and 1999-2000 2001 NAMCS and NHAMCS data

72. Where to get more information Ambulatory Care information booth Ambulatory Care website Call Ambulatory Care Statistics Branch at (301) 458-4600 Academy for Health Services Research and Health Policy seminar Fall, 2002

73. http://www.cdc.gov/nchs/about/major/ahcd/ahcd1.htm

74. NCHS Research Data Center

75. Why the Research Data Center? Have access to information not available on public use files Patient: zip code linked income, education, or urbanicity status Provider: physician sex and age, board certification, teaching hospital Geographic: state and county codes

76. Data Center- cont. Can merge with contextual variables (e.g., ARF, NHIS, Census, NHDS) Health status level HMO penetration Physician and specialist supply Medicaid reimbursement Air quality Percent in poverty

77. Data Center rules Submit a proposal Cannot use data to identify patients or providers or geographic location of providers Cannot remove data files Fee – onsite / remote / file construction

78. I need more information ! Visit the Research Data Center booth E-mail: [email_address] Website: www.cdc.gov/nchs/r&d/rdc.htm Call (301) 458-4277

79. Thank You Linda McCaig – NHAMCS data [email_address] David Woodwell – NAMCS data [email_address]