Stress testing: national patterns and predictors of test ordering

To determine predictors of ordering of exercise stress tests.

Because exercise stress testing is routinely used and widely available and may have an effect on subsequent evaluation of and therapy for heart disease, understanding current patterns of ordering exercise stress tests may have important implications for national health care costs. We hypothesized that factors other than clinical condition exert an influence on ordering of exercise stress tests.

Data from the 1991 and 1992 National Ambulatory Medical Care Surveys conducted by the National Center for Health Statistics were analyzed by means of multivariate logistic regression.

In an estimated 1.12 billion adult visits to office-based physicians in the United States (95% confidence interval [CI], 1.07-1.16 billion), 6.2 million (95% CI, 4.8-7.6 million) exercise stress tests were ordered. After adjustment for clinical and nonclinical variables associated with the office visit, cardiologists were 3.7 (95% CI, 2.7-5.1) times more likely to order exercise stress tests than were internists, who were more likely to order an exercise stress test than were family and general practitioners (0.5, 95% CI, 0.3-0.7). Nonclinical factors associated with increased ordering of exercise stress tests included male sex (odds ratio 2.5; 95% CI, 2.0-3.2), white race (odds ratio 1.6; 95% CI, 1.1-2.3), new referral status (odds ratio 3.8; 95% CI, 2.5-5.8), and private insurance (odds ratio 1.4; 95% CI, 1.1-1.8). Medicare recipients were about half (95% CI, 0.4-0.9) as likely as other patients to have an exercise stress test ordered.

Factors other than clinical condition exert an influence on ordering of exercise stress tests and may represent modifiable elements associated with appropriate practice.