The Wechsler Adult Intelligence Scale-III and malingering in traumatic brain injury: classification accuracy in known groups.

A known-groups design was used to determine the classification accuracy of Wechsler Adult Intelligence Scale-III (WAIS-III) variables in detecting malingered neurocognitive dysfunction (MND) in traumatic brain injury (TBI). TBI patients were classified into the following groups: (a) mild TBI not-MND (n = 26), (b) mild TBI MND (n = 31), and (c) moderate/severe (M/S) TBI not-MND (n = 26). A sample of 80 general clinical patients was used for comparison. Verbal IQ, Verbal Comprehension Index, and Working Memory Index detected approximately 25% of malingerers with a false positive (FP) error rate of approximately 5% in the mild TBI group. Comparable FP rates were obtained in M/S TBI. FP rates for Performance IQ, Perceptual Organization Index, and Processing Speed Index were acceptable in mild TBI but too high in M/S TBI. Previously studied specialized indicators (Vocabulary minus Digit Span and the Mittenberg formula) failed to differentiate malingerers from nonmalingerers. The clinical application of these findings is discussed.