Validation of a specific activity questionnaire to estimate exercise tolerance in patients referred for exercise testing

Background Physical activity and symptom questionnaires have been used as s urrogates for exercise testing to estimate a patient's functional capacity and to individualize an exercise testing protocol in accordance with exerci se testing guidelines. To validate these approaches, they must be compared with measured oxygen uptake (peak VO2). Methods Before exercise testing was performed, a brief, self-administered q uestionnaire (Veterans Specific Activity Questionnaire [VSAQ]) was given to 337 patients referred for exercise testing for clinical reasons. The VSAQ was used to estimate exercise tolerance on the basis of symptoms during dai ly activities to individualize ramp rates on the treadmill so that the test duration would be approximately 10 minutes. Clinical and demographic varia bles were added to the VSAQ responses in a stepwise regression model to det ermine their ability to predict both directly measured peak VO2 and peak me tabolic equivalents (METs) predicted from the treadmill workload. Results The mean exercise time was 9.6 +/- 3 minutes. Responses to the VSAQ and age were the strongest predictors of both measured and predicted exerc ise capacity. Small but significant contributions to the explanation of var iance in bath measured and estimated METs were made by resting heart rate, forced expiratory volume in I second expressed as a percentage of normal, e xercise capacity predicted for age, and body mass index. The multiple R val ues from the regression equations for measured and estimated METs were 0.58 and 0.72, respectively. Conclusions Estimating a patient's symptoms associated with daily activitie s along with age are the strongest predictors of a patient's exercise toler ance. The VSAQ, combined with pretest clinical data, predicts the estimated MET value from treadmill speed and grade better than directly measured MET s do. When used for estimating a patient's symptom limits to individualize ramp rates on a treadmill, this approach yields an appropriate test duratio n in accordance with recent exercise testing guidelines.