Introduction

The 6-minute walk test (6MWT) is a commonly used field test to assess functional exercise capacity in COPD patients. The distance walked in 6 min (6MWD) improves in the majority of patients when the test is performed a second time on separate days or the same day. Little is known about the reproducibility of the 6MWT in COPD patients on a 20-meter course specifically.

Aims

This study aimed to assess the reproducibility of the 6MWT on a 20 meter course in patients with COPD.

Methods

A subset of patients with COPD (FEV1/FVC<70%) from the Canadian Cohort Obstructive Lung Disease study was used. Two 6MWTs were performed on a 20-meter course with standardized instructions and encouragements. The threshold to determine improvement was the upper limit of the clinically important change (UL-CIC) of ?42m. A Bland and Altman plot was used to assess reproducibility.

Results

401 patients were analysed (61% male, age: 68.4±9.7 years,  BMI: 27.3±4.5 kg/m², FEV₁:83.4±18.2 %pred). Only 21 patients (5%) were considered improvers (mean improvement 59.7±14.4m).

The Bland and Altman plot indicated that the 95% limits of agreement (-38.8 - 52.9 meters) exceed the UL-CIC (Fig 1).

Conclusion

Since the limits of agreement between the two tests exceed the UL-CIC it is indicated to perform at least two 6MWT?s to assess a patients? 6MWD on a 20-meter course.