Abstract
Background: We have previously described clinically relevant cut-points for quadriceps maximal voluntary contraction normalised to height squared (QMVC/ht2: female <5.99kg/m2; male <8.30kg/m2) that predict inability to stand from sitting in patients with chronic respiratory disease (Canavan et al 2015 AJRCCM 192(3):395-7). The aim of this study was to further validate these cut-points in patients with COPD by determining their association with all-cause mortality.
Methods: QMVC/ht2 of the dominant leg was measured in 729 patients with stable COPD between 2011-2015. Vital status was checked at 01/01/2016 and survival assessed using a Kaplan-Meier plot and a log-rank test for trend.
Results: Patients (61% male) had a mean (SD) age 69 (10) years, BMI 28 (6) kg/m2, MRC dyspnoea score 3 (1) and FEV1 49 (21) % predicted. Baseline QMVC was 26 (10) kg / 9.43 (3.2) kg/m2. Overall, median follow-up was 961 days and 95 deaths (13%) occurred. The survival distributions were significantly different for patients above and below the cut points, X2 (1) = 4.895, p=0.027 (Figure 1). Mean survival time was 1468 days and 1227 days respectively.
Conclusion: Quadriceps muscle voluntary contraction normalised to height squared is associated with survival in COPD, providing further evidence of the clinical relevance of previously identified cut-points.
- Copyright ©the authors 2016