Five-Repetition Sit-to-Stand Test: Responsiveness and Minimal Important Difference in Idiopathic Pulmonary Fibrosis

Rationale: Standing from a sitting position is an important activity of daily living. The five-repetition sit-to-stand test (5STS) is a simple physical performance test that measures the fastest time taken to stand five times from a chair with arms folded. It can be measured in most healthcare settings and at home, where traditional field walking tests may not be possible. The 5STS has been validated in community-dwelling older adults and people with chronic obstructive pulmonary disease, but data in idiopathic pulmonary fibrosis (IPF) are limited.Objectives: The aims of this cohort study were to establish the construct validity, responsiveness to pulmonary rehabilitation (PR), and minimal important difference (MID) of the 5STS in IPF.Methods: In 149 people with IPF, we compared the 5STS with measures of lung function, exercise capacity, quadriceps strength, breathlessness, and health-related quality of life. Responsiveness and effect sizes were determined by measuring the 5STS before and after PR. The MID was estimated using anchor- and distribution-based methods.Results: The 5STS correlated significantly with incremental shuttle walk test (ISW) (r = -0.55), isometric quadriceps maximum voluntary contraction (QMVC) (r = -0.45), Medical Research Council dyspnea scale score (r = 0.40), Chronic Respiratory Questionnaire-Total (r = -0.21), and King's Brief Interstitial Lung Disease Questionnaire-Total (r = -0.21) but not forced vital capacity percentage predicted or quadriceps one-repetition maximum (1RM). There was a significant but very weak correlation between change in 5STS and changes in Medical Research Council (r = 0.18), ISW (r = -0.21), and Chronic Respiratory Questionnaire-Total (r = -0.26) but no significant correlation with change in 1RM (r = -0.12) or QMVC (r = -0.18). 5STS time improved with PR (median [25th percentile, 75th percentile] change, -1.97 [-3.47, -0.62] s; P < 0.001). The effect size for the 5STS was 0.66 and higher than quadriceps 1RM, QMVC, and ISW. The mean (range) MID estimate was -1.93 (-1.85 to -2.10) seconds.Conclusions: In people with IPF, the 5STS is a valid physical performance measure that is responsive to exercise-based interventions and suitable for use in most healthcare settings.