Six-minute walk test versus two-minute walk test in children with Duchenne muscular dystrophy: Is more time more information?

Background/purpose: The six minute walk test is a widely accepted primary outcome parameter in most studies in Duchenne muscular dystrophy (DMD). To compare information obtained by the six minute walk distance (6MWD) test and the two minute walk distance (2MWD) in patients with DMD, a cohort of 13 voluntary DMD boys did a repeated six minute walking test.

Methods: Patients had to be ambulatory with a physical disability according to Levels 1-3 on the Vignos-Scale for lower extremity. Measurements were taken at one minute intervals. Reliability was measured by intraclass correlation.

Results: Test-retest reliability for 6MWD and 2MWD in two different age classes was very good for both subgroups. Test-retest-reliability was lower in patients with more advanced disability in both tests. Walking speed remained completely stable from time points 1-6 minutes in the whole study patient collective, which indicates that physical exhaustion is not reached after six minutes even in more disabled patients.

Conclusion: Thus the 6MWD in DMD patients does not give additional information as compared to a 2MWD.