National trends in visits to physician offices and outpatient clinics for angina 1995 to 2010.

BACKGROUND: We asked whether visits to physician offices and hospital outpatient clinics for angina have changed over time and whether more frequent use of certain diagnostic techniques or referrals in this setting may account for such changes. METHODS AND
RESULTS: We combined data from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey to study visits to physician offices and outpatient departments. We calculated both crude and standardized rates for these visits using a modified version of technical specifications published by the Agency for Healthcare Research and Quality. In 1995 to 1998, there were on average 3.6 million office/clinic visits each year for angina among adults in the United States. By 2007 to 2010, this had declined to 2.3 million visits each year. Angina visit rates per 100,000 declined significantly (P<0.05), with the greatest decline from 1995 through 1998 to 2003 through 2007. Coronary atherosclerotic disease diagnoses also declined after 2002. Both stress testing and referring patients out for care doubled during some study periods.
CONCLUSIONS: Office and clinic visits for angina have declined over time. This trend parallels findings for both preventable hospitalization and emergency room visits for angina. Previous research's decline in angina hospitalizations is not likely attributable to decreased referrals to hospital and emergency rooms for diagnosis and management. Although changes in International Classification of Diseases, Ninth Revision, Clinical Modification coding guidelines may explain some of the decline in angina and coronary atherosclerotic disease visits, it seems that other factors such as improved treatment or prevention may have played an additional role.