A specific activity questionnaire to measure the functional capacity of cardiac patients

Exercise testing is often performed in persons with cardiac disease to measure their functional capacity. Physical activity questionnaires assessing functional capacity have been used a low-cost and convenient alternative to exercise testing, but have not been well validated against measured oxygen consumption in a cardiac population. This study assesses the ability of a simple, 13-item activity questionnaire, known as the Specific Activity Questionnaire (SAQ), to measure functional capacity prospectively in a large sample of cardiac patients. Ninety-seven consecutive cardiac outpatients (85 men and 12 women aged 59 +/- 10 years [mean +/- SD]) completed the SAQ before an elective symptom-limited treadmill test. Subjects returned within 10 days to repeat the treadmill test, following the same protocol, with the additional measurement of peak oxygen consumption, VO2 (ml x kg(-1)min(-1)), using open circuit spirometry. The SAQ score was significantly related to measured peak VO2(r=0.57, p<0.001). Stepwise multiple linear regression analysis found that the addition of patient age, height, and body weight to SAQ score improved the measurement of peak VO2, accounting for 51% of the sample variance (R=0.71, p<0.001). Peak VO2 was obtained from the following regression formula: [formula: see text]. Thus SAQ, a simple 13-item self-administered activity questionnaire, is able to provide a moderately good measure of functional capacity in cardiac patients and may be useful tool in studies of the cardiac population when formal exercise testing is impractical or uneconomical.