Working Memory and Intelligence Are Associated with Victoria Symptom Validity Test Hard Item Performance in Patients With Intractable Epilepsy

Abstract

Loring et al. (Journal of clinical and experimental neuropsychology, 2005:27;610–617) observed relationships between VSVT hard item performance and IQ and memory indices in epilepsy surgical candidates, with a potential confound of low FSIQ on VSVT performance. The present study replicated the Loring et al. study in a larger sample and extended their findings by examining the relationships among VSVT performance, FSIQ, and working memory. A total of 404 patients with medically intractable epilepsy completed a comprehensive neuropsychological assessment. Differences in WAIS-III and WMS-III performance were examined as a function of VSVT hard score categories as determined by Grote et al. (2000)--that is, valid, > 20/24; questionable, 18–20; or invalid, < 18. Quantile regression models were constructed to compare the strength of the relationship between FSIQ and VSVT at various points of the FSIQ distribution. Linear regression analyses examined working memory as a potential mediator between FSIQ and VSVT performance. The invalid group performed more poorly than the valid and questionable groups on multiple measures of intelligence and memory. The strength of the relationship between FSIQ and VSVT hard item performance decreased as FSIQ increased, and working memory mediated this relationship. Results suggest VSVT hard item scores may be impacted by working memory difficulties and/or low intellectual functioning.

Performance Validity Testing in Multiple Sclerosis

“…Conversely, nonvalid PVT performance could reflect greater disease severity or relate to cognitive factors specific to MS. In addition to Suchy and colleagues' (2012) findings that nonvalid VSVT performance related to earlier symptom onset in MS, studies in other populations have shown associations between VSVT performance and measures of processing speed, working memory, and episodic memory (Loring, Larrabee, Lee, & Meador, 2007;Macciocchi, Seel, Alderson, & Godsall, 2006;Keary et al, 2013), all of which are cognitive functions that are often affected in MS (Chiaravalloti & DeLuca, 2008).…”

“…PVT performance has been well-characterized in select patient groups, including mild traumatic brain injury (mTBI) and presurgical epilepsy patients. Prior studies have shown relatively low rates of PVT failure among presurgical epilepsy patients, and this group is often used to represent individuals without presumed external incentives to underperform on neuropsychological testing (Grote et al, 2000;Loring, Lee, & Meador, 2005;Keary et al, 2013). Conversely, a large proportion of patients with mTBI demonstrate lower than expected performance on neuropsychological testing and reduced scores on PVT measures, which is likely due to relatively higher rates of litigation involvement (Greiffenstein, 2009;Belanger, Curtiss, Demery, Lebowitz, & Vanderploeg, 2005;Binder & Rohling, 1996;Mittenberg, Patton, Canyock, & Condit, 2002;Bianchini, Curtis, & Greve, 2006;Green, Rohling, Lees-Haley, & Allen, 2001).…”

Effort, symptom validity testing, performance validity testing and traumatic brain injury

“…Instead, clinicians will need to consider the possibility that lower performance … may be due to intellectual or working memory limitations (p. 321), irrespective of SVT findings. These findings point to the limits of hard-and-fast rules of distinguishing valid versus invalid test performance based solely on a SVT cut score without, as Keary et al [ 67 ] state, looking ‘… for convergence of findings’ (p. 321).…”

“…In a somewhat similar study, Keary et al [ 67 ] examined patients with intractable epilepsy who were potential candidates for surgery with no know external incentive to malinger. In this cohort they examined three SVT performance findings: Valid (meaning at or above cut-score), Questionable (substantially above chance, but below the SVT cut-point) and Invalid (substantially below the cut point).…”

“…Furthermore, Keary et al [ 67 ] observed that both working memory and intellectual level were related to SVT performance, stating the following: … the cognitive profile should not automatically be judged invalid. Instead, clinicians will need to consider the possibility that lower performance … may be due to intellectual or working memory limitations (p. 321), irrespective of SVT findings.…”