DETERMINING NEUROPSYCHOLOGICAL IMPAIRMENT USING ESTIMATES OF PREMORBID INTELLIGENCE - COMPARING METHODS BASED ON LEVEL OF EDUCATION VERSUS READING SCORES

When inferring brain dysfunction, test scores are typically compared t o normative data based on estimates of premorbid intelligence (e.g., b y educational level or reading scores). However; these methods are lik ely to lead to differing results, with important diagnostic and forens ic implications. The current study compared estimates of impairment (r eported in z-scores) based on educational level versus reading scores in a population,vith traumatic br-ain injury The study included 174 pa tients (M age = 27.3; M education = 12.3) evaluated as outpatients at a university hospital rehabilitation department. Wilcoxen ranked sign tests indicated that tile true methods yielded estimates that were sta tistically different (p < .0001) for all variables. The education base d method yielded greater estimates of impairment than the reading scor e method for WAIS-R FIQ, Grip Strength, and Finger Tapping, with a pat tern of generally consistent impairment across cognitive/motor areas ( z-score range = -0.59 to -.97). In contrast, the reading score based m ethod yielded greater estimates of impairment in processing speed (Tra ils A) and flexibility (Trails B), with a wider range of impairment no ted between cognitive and motor domains (z-score range = +0.21 to -2.9 5). Clinical implications are discussed. (C) 1997 National Academy of Neuropsychology. Published by Elsevier Science Ltd.