1973 to 1981, 1985, 1989 to present
Annual, except for 1982 to 1984 and 1986 to 1988
Mode of Collection
Multi-stage probability sample survey: in-person computer-assisted personal interviews (CAPI) with participating physicians; physicians complete forms for a sample of office visits during an assigned reporting period.
The National Ambulatory Medical Care Survey (NAMCS) provides national data about the provision and use of medical care services in the United States using information collected from medical records. All 50 states and the District of Columbia have been included in the survey since 1989.
Data are collected on the type of providers seen; reason for visit; diagnoses; drugs ordered, provided, or continued; and selected procedures and tests ordered or provided. Other data collected include patient demographics, method of payment, and selected characteristics of physician practices.
Patient encounters in the offices of non-federally employed, office-based, patient care physicians, including physicians in prepaid practices (e.g., Health Maintenance Organizations) are included. Excluded are telephone contacts and nonoffice visits; visits to hospital-based physicians, specialists in anesthesiology, pathology, and radiology, and physicians primarily engaged in teaching, research, or administration.
Public health laboratories in 50 states and 4 local health departments submit Salmonella isolates from clinical specimens from humans to CDC NARMS for antimicrobial susceptibility testing (AST). The laboratories in 10 state health departments participating in the Foodborne Diseases Active Surveillance Network (FoodNet) also submit Campylobacter isolates. Domestically-acquired Campylobacter infections (i.e., no international travel in the 7 days before illness onset) are identified using travel information available from FoodNet. CDC tests isolates for susceptibility to a panel of antimicrobial drugs representing drug classes that are important in human and veterinary medicine. AST results are interpreted using criteria from the Clinical and Laboratory Standards Institute when available. Nontyphoidal Salmonella excludes serotypes Typhi, Paratyphi A, Paratyphi B (i.e., tartrate negative isolates), and Paratyphi C. C. jejuni is the most common species causing Campylobacter infections in humans.
Response Rates and Sample Size
The physician and visit sample sizes have varied over the years. In 2015, the number of eligible physicians was 4,910; the number of visits included was 28,332; and the unweighted response rate was 29%.
The NAMCS patient record form is modified approximately every 2 to 4 years to reflect changes in physician practice characteristics, patterns of care, and technological innovations. Sample sizes vary by survey year. For some years, it may be appropriate to combine 2 or more years of data when examining relatively rare populations or events.