Repeatability of the 6-Minute Walk Test in Adolescents and Adults With Cystic Fibrosis

OBJECTIVE: To determine the repeatability of the 6-minute walk test (6MWT) in adolescents and adults with cystic fibrosis (CF).

METHODS: This was a prospective cross-sectional study. We included consecutive patients ages ≥ 15 years attending an adult CF program. The patients underwent the 6MWT, pulmonary function tests, and clinical evaluation. The second 6MWT was performed following a rest period of 60 min.

RESULTS: Thirty-one patients were included. The mean ± SD age was 23.5 ± 6.7 y, and the mean FEV₁ was 61 ± 28% of predicted. The mean ± SD walked distance in the first 6MWT was 583.6 ± 68.6 m and in the second 6MWT was 590.0 ± 72.2 m. The mean difference between the first and second 6MWT was −6.5 m, with limits of agreement between −74.9 m and 61.9 m, and the coefficient of variation was 4.3%. The mean oxygen desaturation in the first 6MWT was 2.5 ± 4.5%, and in the second test it was 1.8 ± 4.0%. The mean difference between the first and second test was 0.6%, and the coefficient of variation was 104%.

CONCLUSIONS: Although the 6MWT distance was reproducible, the wide limits of agreement exceeded the minimum important difference for this test. These findings indicate that, in the routine evaluation of CF patients, at least two 6MWTs are required on any testing occasion to obtain a reliable estimate of the 6MWT distance.