Adequacy of simple measures for characterizing impairment in upper limb strength following stroke.

Simple measures are sometimes used to characterize weakness in the upper limb after stroke, but their reliability and validity remain uncertain. Here, we examined the adequacy of three measures relative to dynamometer measurements of 26 patients (15 women and 11 men, M age=70.1 +/- 11.7 yr.) with acute stroke. The strength of the involved upper limb was characterized using the National Institutes of Health Stroke Scale: Motor Functions-Arm (drift test), the Stroke Impact Scale: Arm and Hand (self-report), and objective dynamometry. Correlations between the simple measures and dynamometry were significant (r(s)=.70-.87). However, none of the 8 patients who achieved the best NIH scale-Arm score (0: no drift) self-reported having "a lot of strength." Dynamometry indicated that the strength of these patients was less than 50% of that expected according to published norms. The three simple measures examined had convergent validity, but drift, as scored on the NIH scale, was not sensitive to mild or moderate weakness of the upper limb after stroke.