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

Abstract

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, including the home where traditional field walking tests may not be possible. The 5STS has been validated in community-dwelling older adults and people with COPD, but data in idiopathic pulmonary fibrosis (IPF) are limited. Objective: 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 5STS to measures of lung function, exercise capacity, quadriceps strength, breathlessness and health-related quality of life. Responsiveness and effect sizes were determined by measuring 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 contract (QMVC) (r=-0.45), Medical Research Council (MRC) score (r=0.40), Chronic Respiratory Questionnaire (CRQ)-Total (r=-0.21) and King’s Brief Interstitial Lung Disease-Total (r=-0.21) but not forced vital capacity %predicted or quadriceps 1-repetition maximum (1RM). There was a significant but very weak correlation between change in 5STS and change in MRC (r=0.18), ISW (r=-0.21) and CRQ-Total (r=-0.26) but no significant correlation with change in 1RM (-0.12) or QMVC (r=-0.18). 5STS time improved with PR (median (25th, 75th centile) change: -1.97 (-3.47, -0.62) seconds; p<0.001). The effect size for 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.