Prevalence of specific types of arthritis and other rheumatic conditions in the ambulatory health care system in the United States, 2001-2005.

Objective: To estimate the overall prevalence of medically-treated arthritis and other rheumatic conditions (AORC) for adults, the prevalence of specific medically-treated conditions, and the overall annual number of visits for these conditions in the ambulatory health care system.

Methods: We used data from the 2001-2005 National Ambulatory Medical Care Survey and 2001-2005 National Hospital Ambulatory Medical Care Survey to estimate annual ambulatory health care visits for the International Classification of Diseases, Ninth Revision, Clinical Modification codes thought to represent AORC. Using data on the number of prior annual visits per patient per condition, we converted the visit estimates into prevalence estimates of adults age > or =18 years with medically-treated AORC overall and for specific conditions.

Results: The overall prevalence estimate of adults with medically-treated AORC was 29,150,000 adults (95% confidence interval [95% CI] 26,473,000-31,826,000) and accounted for 77,887,300 ambulatory care visits (95% CI 71,266,000-84,508,000). The top 5 most prevalent conditions were osteoarthritis and allied disorders, unspecified joint disorders, peripheral enthesopathies, unspecified arthropathies, and other disorders of synovium, tendon, or bursa.

Conclusion: The advantage of our approach is that it uses existing rather than expensive new surveys for tracking the prevalence of medically-treated AORC overall and tracking the prevalence of difficult to measure specific conditions. The estimates are data based and national in scope. More relevantly, they better estimate the numbers of persons whose AORC impacts on the ambulatory health care system.