Veterans Specific Activity Questionnaire (VSAQ): a new and efficient method of assessing exercise capacity in patients with pulmonary arteriovenous malformations

INTRODUCTION: Assessment of performance status is an important component of clinical management of patients with pulmonary arteriovenous malformations (PAVMs). Usual methods are time-consuming and insensitive to variations within normal or supranormal exercise capacity. METHODS: The Veterans Specific Activity Questionnaire (VSAQ) was modified to facilitate completion by patients independently. Patient-reported activity limitations were converted to the Medical Research Council (MRC) Dyspnoea Scale, New York Heart Association (NYHA) classification and metabolic equivalents (METs) in which 1 MET equals the consumption of 3.5 mL O(2) per kilogram of body weight per minute. RESULTS: The study population consisted of 71 patients with PAVMs aged 20–85 (median 52) years. Oxygen saturation (SaO(2)) was 80%–99.5 % (median 96%), and haemoglobin was 73–169 g/L in women and 123–197 g/L in men (p<0.0001). Arterial oxygen content (CaO(2)) (1.34 × [haemoglobin × SaO(2)]/100) was maintained unless iron deficiency was present. Most patients (49/71, 69%) did not need to stop until activities more energetic than walking briskly at 4 mph were achieved (6.4 km per hour, VSAQ >5, MRC Dyspnoea Scale 1 or 2, NYHA class I). SaO(2) was inversely associated with the MRC Dyspnoea Scale and NYHA class, but not the VSAQ. Raw VSAQ scores captured a marked difference between men and women. METs were also higher in men at 3.97–15.55 (median 8.84) kcal/kg/min, compared with 1.33–14.4 (median 8.25) kcal/kg/min (p=0.0039). There was only a modest association between METs and SaO(2) (p=0.044), but a stronger association between METs and haemoglobin (p =0.001). In crude and sex-adjusted regression, the CaO(2) was more strongly associated with METs than either SaO(2) or haemoglobin in isolation. CONCLUSION: The VSAQ, capturing patient-reported outcome measures, is an efficient and quantifiable measure of exercise capacity that can be readily employed in clinical services particularly where patients have normal to high exercise tolerance. In the PAVM population, exercise capacity reflects haemoglobin and CaO(2) more than SaO(2), even where SaO(2) measurements are low.