Increase in walk distance is not enough evidence to add a walk to the 6-minute walk test

To the Editors:

We read with interest the work of Hernandes et al. [1]. The authors performed a cross-sectional analysis using data from 1,514 patients with moderate-to-very severe chronic obstructive pulmonary disease who performed 6-min walks on consecutive days and recommended that, because the distance of the second walk was longer than that of the first, two walks should be performed [1]. Their finding that the walk distance increases by 7% on the second walk (27-m increase from a baseline of 391 m) validates our previous findings and adds new knowledge about the variables that predict improvement in walk distance [2]. These predictors of improvement may be helpful in identifying …