Prognosis in chronic obstructive pulmonary disease (COPD) is poorly predicted by indices of air flow obstruction, because other factors that reflect the systemic nature of the disease also influence prognosis.Objective:
To test the hypothesis that a reduction in quadriceps maximal voluntary contraction force (QMVC) is a useful predictor of mortality in patients with COPD.Methods:
A mortality questionnaire was sent to the primary care physician of 184 patients with COPD who had undergone quadriceps strength measurement over the past 5 years. QMVC was expressed as a percentage of the patient’s body mass index. The end point measured was death or lung transplantation, and median (range) follow-up was 38 (1–54) months.Results:
Data were obtained for 162 patients (108 men and 54 women) with a mean (SD) percentage of forced expiratory volume in 1 s (FEV1) predicted of 35.6 (16.2), giving a response rate of 88%. Transplant-free survival of the cohort was 93.5% at 1 year and 87.1% at 2 years. Cox regression models showed that the mortality risk increased with increasing age and with reducing QMVC. Only age (HR 1.72 (95% CI 1.14 to 2.6); p = 0.01) and QMVC (HR 0.91 (95% CI 0.83 to 0.99); p = 0.036) continued to be significant predictors of mortality when controlled for other variables in the multivariate analysis.Conclusion:
QMVC is simple and provides more powerful prognostic information on COPD than that provided by age, body mass index and forced expiratory volume in 1 s.