Observed Versus Estimated IQ as an Index of Malingering in Traumatic Brain Injury: Classification Accuracy in Known Groups

Abstract

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.

Keywords:

• Barona index
• intelligence
• malingering
• neuropsychological assessment
• response bias
• traumatic brain injury
• Wechsler scales

ACKNOWLEDGMENTS

This project is one component of a much larger data collection project. Our research assistants, including Jeffrey Love, Matthew Heinly, Kelly Curtis, and Adrianne Brennan, have been tireless and their efforts are much appreciated.

Notes

CVA = cerebrovascular accident; TBI = traumatic brain injury.

TBI = Traumatic brain injury; MND = Malingered Neurocognitive Dysfunction.

^abc Row means with the same letter are not significantly different from each other.

¹All F-values were significant at alpha ≤ .001.

TBI = traumatic brain injury; VIQ = Verbal Intelligence Quotient; PIQ = Performance Intelligence Quotient; FSIQ = Full Scale Intelligence Quotient; e = estimated based on Barona formula; MND = Malingered Neurocognitive Dysfunction; sd = standard deviation; diff = estimated minus observed difference score.

TBI = traumatic brain injury; VIQ = Verbal Intelligence Quotient; PIQ = Performance Intelligence Quotient; FSIQ = Full Scale Intelligence Quotient; e = estimated based on Barona formula; MND = Malingered Neurocognitive Dysfunction; sd = standard deviation; diff = estimated minus observed difference score.

TBI = Traumatic brain injury; Not-MND = all TBI not classified as malingering or indeterminate; MND = combined Probable and Definite Malingered Neurocognitive Dysfunction; M/S = moderate or severe TBI; CVA = cerebrovascular accident; Mem = Memory Disorder; Total Not-MND = all patients including TBI not classified as malingering or indeterminate.

TBI = traumatic brain injury; + PP = positive predictive power for pretest odds of .20, .30, and .40.; FP = false positive error rate; Sens = sensitivity; LR = likelihood ratio.

FP = false positive error rate; Sens = sensitivity; LR = likelihood ratio.