The Reliability, Precision & Clinically Meaningful Change Of Walking Assessments In MS

Background:

Assessing walking impairment in those with multiple sclerosis (MS) is common, however little is known about the reliability, precision and clinically important change of walking outcomes.

Objectives:

To determine the reliability, precision and clinically important change of the Timed25-Foot Walk (T25FW), Six-Minute Walk (6MW), Multiple Sclerosis Walking Scale-12 (MSWS-12) and accelerometry.

Methods:

Data were collected from 82 persons with MS at two-time points, six months apart. Analyses were undertaken for the whole sample and stratified based on disability level and usage of walking aids. Intraclass correlation coefficient (ICC) analyses established reliability; standard error of measurement (SEM) and coefficient of variation (CV) determined precision; and minimal detectable change (MDC) defined clinically important change.

Results:

All outcome measures were reliable with precision and MDC varying between measures in the whole sample: T25FW ICC=0.991, SEM=1s, CV=6.2%, MDC=2.7 s (36%); 6MW ICC=0.959, SEM=32m, CV=6.2%, MDC=88m (20%);  MSWS-12 ICC=0.927, SEM=8, CV=27%, MDC=22 (53%); accelerometry counts/day ICC=0.883, SEM= 28450, CV=17%, MDC=78860 (52%); accelerometry steps/day ICC=0.907, SEM=726, CV=16%, MDC=2011, (42%). Variation in these estimates was seen based on disability level and walking aid.

Conclusions:

Reliability of these outcomes is good; falling within acceptable ranges. Precision and clinically important change estimates provide guidelines for interpreting these outcomesin clinical and research settings.