Observed versus estimated IQ as an index of malingering in traumatic brain injury: classification accuracy in known groups.

This study examined the classification accuracy of observed WAIS-III VIQ, PIQ, and FSIQ minus Barona-estimate differential scores in the detection of Malingered Neurocognitive Dysfunction (MND) in Traumatic Brain Injury (TBI) using a known-groups design. Two hundred eleven TBI patients were assigned to one of three groups: Not-MND (n = 87), Indeterminate (n = 68), and MND (n = 56). A General Clinical Sample of 93 no-incentive patients (e.g., CVA, memory disorder) was also included to better study specificity. The VIQ differential accurately differentiated MND from Not-MND TBI patients regardless of injury severity. The PIQ differential was only accurate in mild TBI and did not add incremental validity to the VIQ differential. This study indicates that VIQ declines of greater than 24 points are rare except in very severe TBI. Particularly in mild TBI, such differentials likely indicate intentional suppression of WAIS-III performance consistent with MND. Clinical application is discussed.