Discrepancy between predicted and obtained WAIS-R IQ scores discriminates between traumatic brain injury and insufficient effort

This study examines how well the discrepancy between predicted and obtained Wechsler Adult Intelligence Scale- Revised (WAIS-R) scores discriminate be tween insufficient effort (IE) and traumatic brain injury (TBI). The 27 IE patients performed significantly more poorly on the WAIS-R than the 48 mode rate-severe TBI patients. Premorbid IQs were calculated with formulae that use demographics (Barona Index) or demographics and WAIS-R performance (Bes t-3 and the Oklahoma Premorbid Intelligence Estimation). Predictions were s imilar on the Barona, but IE patients' predicted IQs were lower than TBIs f or measures with a performance component, IE patients demonstrated a greate r discrepancy score (i.e., predicted IQ - obtained IQ) than TBIs; variable levels of sensitivity and specificity were obtained when discriminate funct ions were developed on these scores. The potential advantage of using discr epancy scores Versus performance-based measures to detect insufficient effo rt is discussed.