Simple functional performance tests and mortality in COPD

Milo A. Puhan, Lara Siebeling, Marco Zoller, Patrick Muggensturm, Gerben ter Riet

Exercise tests are important to characterise chronic obstructive pulmonary disease patients and predict their prognosis, but are often not available outside of rehabilitation or research settings. Our aim was to assess the predictive performance of the sit-to-stand and handgrip strength tests. The prospective cohort study in Dutch and Swiss primary care settings included a broad spectrum of patients (n=409) with Global Initiative for Chronic Obstructive Lung Disease stages II to IV. To assess the association of the tests with outcomes, we used Cox proportional hazards (mortality), negative binomial (centrally adjudicated exacerbations) and mixed linear regression models (longitudinal health-related quality of life) while adjusting for age, sex and severity of disease. The sit-to-stand test was strongly (adjusted hazard ratio per five more repetitions of 0.58, 95% CI 0.40-0.85; p=0.004) and the handgrip strength test moderately strongly (0.84, 95% CI 0.72-1.00; p=0.04) associated with mortality. Both tests were also significantly associated with health-related quality of life but not with exacerbations. The sit-to-stand test alone was a stronger predictor of 2-year mortality (area under curve 0.78) than body mass index (0.52), forced expiratory volume in 1 s (0.61), dyspnoea (0.63) and handgrip strength (0.62). The sit-to-stand test may close an important gap in the evaluation of exercise capacity and prognosis of chronic obstructive pulmonary disease patients across practice settings.