Reproducibility of the 6-Minute Walk Test on a 20-Metre Course in Community Dwelling Adults With Chronic Obstructive Pulmonary Disease

Purpose: The 6-minute walk test (6MWT) assesses physical capacity in people with COPD. The distance walked during six minutes (6MWD) is the primary outcome. In clinical practice, 20-metre courses are often used instead of recommended 30-metre. This study aimed to investigate reproducibility of the 6MWT on a 20-metre course in community dwelling adults with COPD. Method: We analyzed 350 participants with COPD, who completed two 6MWTs. Agreement between tests was assessed using a Bland-Altman plot. Participants were divided into improvers and non-improvers based on the upper limit of the 20-metre course minimal important difference (MID) (47 metres). Logistic regression analyses were performed to identify factors affecting reproducibility of 6MWD. Results: Seventeen participants (5%) exceeded the upper limit of the MID in the second 6MWT and were considered improvers. Improvers were younger than non-improvers, had a higher 6MWD and 6-minute distance-saturation product, and a higher proportion had a normal BMI. The Bland-Altman plot showed that the 95% limits of agreement exceeded the MID. Only the presence of cancer as a comorbidity significantly influenced the likelihood of being an improver in 6MWD. Conclusion: This study showed the need to perform at least two 6MWTs on 20-metre courses to obtain a representative 6MWD.