Identification of Malingered Head Injury with WAIS-3 Vocabulary and Digit Span

Abstract Objective: Prior research documents that exaggeration is common in compensable head trauma, and can be identified by intelligence test performance pattern. This study derived a WAIS-3 Vocabulary-Digit Span discriminant function to identify malingering by comparing clinical malingerers and head trauma patients. Method: Fifty-nine malingering litigants were identified by scores on the TOMM, PDRT, WMT, or VSVT that were lower than obtained by any TBI patients in validation studies. Fifty-nine nonlitigants were matched to litigants onWAIS-3 FSIQ (85.53 vs. 85.54). Nonlitigants had a median GCS of 9 and 18 h post-injury coma. Litigants had a median GCS of 15 and median coma less than 1 h. Litigants and nonlitigants obtained FSIQ’s that were lower than demographically estimated premorbid IQ (M= 19 and 12 points) at 30 months versus 9 months post-injury. Vocabulary and Digit Span scores were entered in a stepwise discriminant analysis to determine if groups could be accurately identified. Results: Seventy-five percent of TBI and 76% of malingerers were correctly classified. Discrimination was unrelated to coma length, GCS, CT results, or obtained FSIQ in either group. Discriminant score was significantly correlated with TOMM (r \u3e .47) and VSVT (r \u3e .44) scores in malingerers. Crossvalidation in independent groups of 68 nonlitigating TBI and 108 normals instructed to malinger impairment produced 71% and 77% diagnostic accuracy rates, respectively. Conclusions: Vocabulary and Digit Span performance pattern continues to be useful in identifying malingered head injury. This study was supported by the NAN Clinical Research Grant and an NSU President’s Grant