Intra- and Inter-Rater Reproducibility of Measures of Physical Performance in Patients with COPD

Background: Assessments of functional capacity require considerable time and space and are thus generally not suitable for home-based assessments. Reproducibility measures from tests evaluating functional capacity suitable for home-based assessment are warranted. The aim of this study was to investigate the intra- and inter-rater reproducibility of home-based assessments of the one-minute sit-to-stand test (1MSTS), handgrip strength (HGS), and short physical performance battery (SPPB) in patients with moderate to very severe chronic obstructive pulmonary disease (COPD). Methods: Fifty patients were recruited from an ongoing RCT study prior to the start of the intervention. All patients performed two 1MSTS attempts with 30 min intervals, three HGS attempts, and one SPPB attempt. The procedure was repeated after 7-10 days by a blinded assessor. Results: Fifty patients (29 females; mean (SD): age 71.3 (±7.7) years, FEV1% predicted 37.4 (±14.1), and COPD assessment test score 19.4 (±6.5) were assessed. The 1MSTS intra-rater reliability (intraclass correlation coefficient; ICC_1.1) was 0.95 (lower limit 95% CI: 0.91) and classified as excellent; agreement (standard error of measurement, SEM) was 1.7 repetitions. The inter-rater reliability ICC_1.1 for 1MSTS was 0.91 (lower limit 95% CI: 0.84) and SEM 2.5 repetitions; for HGS it was ICC_1.1 of 0.84 (lower limit 95% CI: 0.74) and SEM 4.2 kg; for SPPB it was ICC_1.1 of 0.86 (lower limit 95% CI: 0.77) and SEM 0.9 points, respectively. Conclusions: The reproducibility of home-based assessment with 1MSTS, HGS, and SPPB in patients with moderate to very severe COPD showed good to excellent intra- and inter-rater reliability and acceptable agreement below the established minimal important change. These findings support the utility and feasibility of these tests as reliable outcome measures in clinical practice and their applicability in home-based settings enabling functional assessments of patients with transportation challenges and mobility limitations.