Evaluating Test-Retest Reliability of Fatigability in Chronic Stroke

The subjective nature of fatigue may contribute to inconsistencies in prevalence rates for post-stroke fatigue. More objective performance fatigue measures may offer a more reliable construct of fatigue. Our goal was to establish test-retest reliability of fatigability in stroke during 6-minute walk (6MW) testing. Relationships between post-stoke fatigability and other constructs were assessed.

Twenty-three hemiparetic stroke survivors underwent two 6MW tests with portable metabolic monitoring performed at least 48 hours apart. Fatigability was defined as ratio of change in walking speed to distance covered during the 6MW. 6MW oxygen consumption (VO₂), peak aerobic capacity (VO₂peak), walking speed over-ground, dynamic gait index, fatigue, falls efficacy, and BMI were measured.

Fatigability was highly correlated between both 6MW trials (ICC = 0.99, p < 0.001) with no significant difference between trials (0.08, p = 0.48). The strongest correlation was between fatigability and 6MW VO₂ trial 1 and 2 (r = 0.92, p < 0.001 and r = 0.95, p < 0.001, respectively). Moderate-to-strong relationships were observed between fatigability for 6MW and fastest-comfortable walking speed (r = -0.82 and -0.77), self-selected walking speed (r = -7.8 and -0.78), 6MW walking speed (r = -0.80 and 0.80, VO₂peak (r = -0.47 and -0.48) (p < 0.001), and DGI (r = -0.70 and -0.68, p < 0.001).

This study establishes test-retest reliability for an objective measure of fatigue in stroke-related disability. The strong correlations between fatigability and other functional measures also provides insight into the contributors underlying fatigability in this population.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01322607.