DETERMINING NEUROPSYCHOLOGICAL IMPAIRMENT USING ESTIMATES OF PREMORBID INTELLIGENCE - COMPARING METHODS BASED ON LEVEL OF EDUCATION VERSUS READING SCORES
B. Johnstone et al., DETERMINING NEUROPSYCHOLOGICAL IMPAIRMENT USING ESTIMATES OF PREMORBID INTELLIGENCE - COMPARING METHODS BASED ON LEVEL OF EDUCATION VERSUS READING SCORES, Archives of clinical neuropsychology, 12(6), 1997, pp. 591-601
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.