BACKGROUND: Early detection of prostate cancer is thought to be effective, and indirect evidence suggests that men aged 50 to 69 years will benefit most while those aged 70 and older will benefit least from it. The goal of our study was to describe usual care patterns for prostate-specific antigen (PSA) testing by primary care physicians in the United States.
METHODS: We analyzed office visits made by adult men to family physicians, general internists, general practitioners, and geriatricians recorded by the 1995 and 1996 National Ambulatory Medical Care Surveys. Our outcome measure was the probability of a primary care physician ordering a PSA test during a visit.
RESULTS: Seventeen percent of the tests reported were among men aged younger than 50 years, 50% were for men aged 50 to 69 years, and 33% were for men aged 70 years and older. The frequency of PSA testing was highest during visits by men aged 60 to 64 years (7.1%), 65 to 69 years (7.0%), 70 to 74 years (7.0%), and 75 to 79 years (6.3%) but lower for men aged older than 80 years (3.1%).
CONCLUSIONS: Our findings suggest that during the mid-1990s prostate cancer screening decisions by primary care physicians were not sensitive to patients’ ages.
Although direct evidence on the effectiveness of prostate cancer screening is not available, a decision model to estimate its benefits and risks provides indirect evidence. That model uses favorable but unproven assumptions to demonstrate that if prostate cancer screening proves effective, men aged 50 to 69 years will benefit most while those aged 70 years and older will benefit least. A decision model by Krahn and colleagues found that prostate cancer screening may result in worse health outcomes, particularly for men aged older than 70 years. To better characterize physician practices that provide the context for the ongoing prostate cancer screening debate, we focused on a large database of outpatient visits to US primary care physicians to examine national age-specific patterns of prostate-specific antigen (PSA) testing.
Methods
Data for this study were obtained from the National Ambulatory Medical Care Surveys (NAMCS) for 1995 and 1996. Those surveys, conducted annually by the National Center for Health Statistics, provide an ongoing assessment of the practices of US office-based physicians. The sampling process made use of the master lists of all US practicing physicians from the American Medical Association and the American Osteopathic Association. A subset of physicians from these lists was randomly selected and stratified by geographic area and specialty. For each participating physician in each year, patient visits during a random week were sampled systematically. Recorded information included patient demographics, reasons for the visit, diagnoses, and tests ordered. Among eligible physicians, annual participation rates averaged 72%. The unit of analysis was the physician-patient visit.
We examined the NAMCS surveys for 1995 and 1996. We focused on primary care physician visits by adult men aged 18 years and older. Primary care physicians included physicians in the specialties of family practice, internal medicine, general practice, and geriatrics. Prostate cancer was identified by an International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) diagnostic code 185.00. We excluded men with prostate cancer, to limit PSA testing to that done for screening or diagnosis. In 1995 and 1996, 708 primary care physicians provided information on 6397 ambulatory visits by adult men without prostate cancer. Estimates of national practices were calculated by weighting data from the sampled visits. Our outcome measure was the probability of a primary care physician ordering a PSA test at any given visit. We also analyzed visits that might be associated with an increased frequency of PSA testing, such as those by men with lower urinary tract symptoms, those who had been diagnosed with benign prostatic hypertrophy (BPH), or those who were seeking a general medical examination. We employed National Center for Health Statistics relative standard error figures to calculate 95% confidence intervals (CIs) for national estimates. Comparisons were tested using continuity adjusted chi-square tests as implemented with Statistical Analysis System (SAS) software. We modified survey weights using proportional scaling with the method of Pothoff and colleagues to determine effective sample sizes.
Results
Extrapolating nationally, there were 7.7 million (95% CI, 6.2 million to 9.2 million) primary care physician visits per year by adult men in the United States during which a screening or diagnostic PSA test was ordered. PSA testing occurred during 3.9% of primary care physician visits by adult men. Of all PSA tests ordered during primary care physician visits, 17% were for men aged younger than 50 years, 50% for men aged 50 to 69 years, and 33% for men aged 70 years and older.