METHODS A Nomogram to Predict Exercise Capacity from a Specific Activity Questionnaire and Clinical Data Jonathan Myers, PhD, Dat Do, BS, William Herbert, PhD, Paul Ribisl, PhD, and Victor F. Froelicher, MD Recent investigations suggested that clinical exercise testing can be optimized by individuaC izing the protocol, depending on the purpose of the test and the subject tested. This requires some knowledge of a patient’s exercise capacity before beghtning the test. The accuracy of a simple physical activity questionnaire and readily available dinical data in predicting subsequent treadmill performance was examined. A brief, setf administered questionnaire (VSAQ) was deveC oped for veterans who were referred to exercise testing for clinical reasons. The VSAQ was designed to determine which specific daily activities were associated with symptoms of cardiovascuiar disease (fatigue, chest pain and shortness of breath). Two hundred twelve consec- utive patients (mean age 62 -c 8 years) referred for maximal exercise testing were studied. Clinical and demographic variables were added to VSAQ responses in a stepwise regression model to determine their ability to predict treadmill per fonnance. Only metabolic equivalents by VSAQ, and age were significant predictors of treadmill performance; these 2 variabies yielded kO.62 (SEE 1.43; p ~O.OOl), and explained 67% of the variance in exercise capacity. 7he regression equation reflecthtg the relation between age, VSAQ and exercise capacity was: achieved met& boiic equivalents = 4.7 + 0.97 (VSAQ) - 0.06 (age). Using this equation, a nomogram was developed. incorporating the VSAQ with the nomogram requires only a few minutes, and yields a reasou ably accurate estimate of a patient’s exercise capacity. Although the present equation is popu iationapecific, a similar approach in different populations may be useful for individualizing pro tocois for clinical exercise testing. (Am J Cardioi 1994;73:591-!599) From the Cardiology Division, Palo Alto Veterans Affairs Medical Center and Stanford University, Palo Alto, California. Manuscript received June 30, 1993; revised manuscript received and accepted September I, 1993. Address for reprints: Jonathan Myers, PhD, Cardiology Division (11 IC), Palo Alto Veterans Affairs Medical Center, 3801 Miranda Av- enue, Palo Alto, California 94304. E xercise testing is performed frequently in patients with heart disease to evaluate cardiopulmonary function, and assess clinical status,therapeuticef- ficacy and patient prognosis. Maximal exercisecapacity, commonly expressed in metabolic equivalents (METS), is 1 of the more important measurements used clinical- ly, owing to its impact on prognostic, vocational and financial concerns.These issuesare of particular impor- tancein the veteran population, because exercise capac- ity is a major determinant of disability. However, max- imal exercisetesting is not feasible in all settingsowing to financial and physical limitations, time restraints and increasedpatient risk. Thus, methodsof assessing func- tional status without exercise testing are desirable in some cases. The New York Heart Association functional classifi- cation is 1 method used to assess the cardiovascularsta- tus of patients with heart disease.’ This system, which classifiespatients according to the degree of symptoms associated with daily activities, has several limitations. First, it divides patients into 1 of 4 categories; thus, it is very general. Second,the degreeto which the system correlates with direct measuresof exercise capacity is unclear. Third, it has been reported that physicians and patients frequently disagree on classifications of activi- ties, which results in patients being misclassified.2-s Goldman et al2 used a specific activity scale consisting of a seriesof questionsconcerning daily activities which were designed to classify patients by functional class. Although its performance was superior to those of the New York Heart Association and Canadian Cardiovas- cular Society6 systems, 32% of patients were incorrect- ly classified, and only a modest correlation (r = 0.66) was observed with treadmill time on the Bruce proto- col. Hlatkey et al7 recently developed the Duke Activi- ty Status Index in which responses concerning physical activities were empirically weighted on the basis of difficulty. These investigators reported a correlation co- efficient between the Duke Activity Status Index and maximal oxygen uptake of r = 0.58 when using a self- administeredquestionnaire;however, the correlation im- proved to r = 0.80, when patients were interviewed personally by a staff member. Other studies, using ac- tivity assessments alone or in combination with clinical or demographic data,have reportedassociations with ex- ercise capacity ranging from r = 0.29 to O.87.2,7-‘” The aim of this study was to enhancethe prediction of exercise capacity using a qu’ stionnaire and clinical data. However, the specific goal was to use this infor- PREDICTING EXERCISE CAPACITY 591