MEASUREMENT PROPERTIES OF THE NIH STROKE SCALE DURING ACUTE REHABILITATION

Background and Purpose The scale of stroke impairment characteristics by Brott and associates, the National Institutes of Health (NIH) Strok e Scale, has been used widely in various studies of stroke outcome; ho wever, the measurement properties of the items applied to patients dur ing medical rehabilitation have not been evaluated thoroughly. This st udy evaluated the extent to which scale items cohere to define a unidi mensional construct and have a useful range for application to patient s during medical rehabilitation. Methods Rating scale (or Rasch) analy sis of the 15 NIH Stroke Scale items was conducted using the BIGSTEPS computer program to evaluate (1) the ran of impairment assessed by the items, (2) the items' coherence with an underlying construct of impai rment, and (3) range of impairment measured in rehabilitation patients . We sought to maximize the range of impairment measured by conducting analyses recursively; at each subsequent step, the worst fitting item was deleted or rescored. The sample comprised 1291 admission and disc harge records from 693 rehabilitation inpatients with stroke. Results Thirteen items arrayed the sample across a sufficient range of impairm ent. The limb ataxia item fit poorly and was deleted; lower ratings fo r this item were associated with higher scores on the total scale. Pup illary response was also deleted because ratings reflected poor congru ence with the total score. Best language was rescored because intermed iate ratings were inconsistently related to the total score. Patients with hemorrhagic strokes had poorer fitting measures than did patients with ischemic strokes. Conclusions The items in a revised NIH Stroke Scale worked well together to define the severity of impairment result ing from stroke that is observed during medical rehabilitation. Direct ions regarding limb ataxia should be modified to indicate untestabilit y due to hemiplegia.