Classification accuracy of the Millon Clinical Multiaxial Inventory-III modifier indices in the detection of malingering in traumatic brain injury

The present study used criterion groups validation to determine the ability of the Millon Clinical Multiaxial Inventory-III (MCMI-III) modifier indices to detect malingering in traumatic brain injury (TBI). Patients with TBI who met criteria for malingered neurocognitive dysfunction (MND) were compared to those who showed no indications of malingering. Data were collected from 108 TBI patients referred for neuropsychological evaluation. Base rate (BR) scores were used for MCMI-III modifier indices: Disclosure, Desirability, and Debasement. Malingering classification was based on the Slick, Sherman, and Iverson (1999) criteria for MND. TBI patients were placed in one of three groups: MND (n = 55), not-MND (n = 26), or Indeterminate (n = 26).The not-MND group had lower modifier index scores than the MND group. At scores associated with a 4% false-positive (FP) error rate, sensitivity was 47% for Disclosure, 51% for Desirability, and 55% for Debasement. Examination of joint classification analysis demonstrated 54% sensitivity at cutoffs associated with 0% FP error rate. Results suggested that scores from all MCMI-III modifier indices are useful for identifying intentional symptom exaggeration in TBI. Debasement was the most sensitive of the three indices. Clinical implications are discussed.