Within-day variability on short and long walking tests in persons with multiple sclerosis

Abstract

ObjectiveTo compare within-day variability of short (10m walking test at usual and fastest speed; 10MWT) and long (2 and 6-minute walking test; 2MWT/6MWT) tests in persons with multiple sclerosis. DesignObservational study. SettingMS rehabilitation and research centers in Europe and US within RIMS (European network for best practice and research in MS rehabilitation). SubjectsAmbulatory persons with MS (Expanded Disability Status Scale 0–6.5). InterventionSubjects of different centers performed walking tests at 3 time points during a single day. Main measures10MWT, 2MWT and 6MWT at fastest speed and 10MWT at usual speed.Ninety-five percent limits of agreement were computed using a random effects model with individual pwMS as random effect. Following this model, retest scores are with 95% certainty within these limits of baseline scores. ResultsIn 102 subjects, within-day variability was constant in absolute units for the 10MWT, 2MWT and 6MWT at fastest speed (+/−0.26, 0.16 and 0.15m/s respectively, corresponding to +/−19.2m and +/−54m for the 2MWT and 6MWT) independent on the severity of ambulatory dysfunction. This implies a greater relative variability with increasing disability level, often above 20% depending on the applied test. The relative within-day variability of the 10MWT at usual speed was +/−31% independent of ambulatory function. ConclusionsAbsolute values of within-day variability on walking tests at fastest speed were independent of disability level and greater with short compared to long walking tests. Relative within-day variability remained overall constant when measured at usual speed.