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CSME|CAPDA Medico-Legal Summit - Sonya Dhillon
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The Assessment and Detection Feigned Symptoms that may persist after a Mild Traumatic Brain Injury: An Analogue Investigation
Sonya Dhillon, MA., Konstantine K. Zakzanis, PhD., R. Michael Bagby, PhD.

These tests are based in empiricism, such that the methods are derived from empirical data. The interpretation of these data is bestowed upon the clinician, to transfer test results into interpretations, which taking into account clinical history, interview information, etc. With respect to the assessment of over reporting of symptoms that may persist following a mild traumatic brain injury (mTBI), the psychologists have available to them different instruments including symptom validity tests (SVTs) and performance validity tests (PVTs). Both sets of instruments utilize different strategies to detect over reporting. In addition, self-report inventories often used in the context of a psychological assessment include in them embedded SVT scales and or indices. Two of the most widely used and omnibus inventories include the Minnesota Multiphasic Personality Inventory 2 Restructured Form (MMPI-2-RF) and the Personality Assessment Inventory (PAI). PVTs on the other hand, are often “stand alone” PVTs. With that said, there are multiple test that seek to measure similar concepts: over reporting of symptoms following the mTBI; it remains unclear which of these tests are the best predictors of this response bias based on diagnostic efficacy metrics (i.e., sensitivity, specificity, positive and negative predictive value). To this end, a simulation study was in which participants were administered a battery of PVTs and embedded SVTs under two different instructions sets: standard instructions (SI) or over-reporting instructions (OR). Participants (N=168) were administered the MMPI-2-RF, PAI and PVTs and instructed to either feign symptoms (i.e., OR instructions) that can persist after an mTBI or respond honestly (i.e., SI instructions). A series of hierarchical logistic regressions were used to a) compared the predictive capacity of the two SVTs, and b) examine the incremental increase in predictive capacity of the SVTs among the PVTs. The Response Bias Scale (RBS) of the MMPI-2-RF was the best predictor relative to all other SVTs and the PVTs while reducing the incidence of type I error, or falsely classifying an individual as OR when they were not. Administering PVTs may help provide help to substantiate the results from the RBS, but are not necessary to improve diagnostic efficiency. As such, the RBS may be used in a neuropsychological evaluation to assess for possible mTBI symptom exaggeration, although the results need to be replicated in other experimental studies and in clinical contexts. Notably, an over-reporting response style should be assessed objectively, while supplementing with clinical history, interview and informant report

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