Analysis of skew, examination of intercorrelations, and determining the optimal threshold for performance invalidity when 10 performance validity tests are administered during a neuropsychological evaluation.

Introduction: This study cross-validates and expands upon previous research by examining the optimal number of PVT failures necessary to determine invalid performance when 10 PVTs are administered during a neuropsychological evaluation. Additionally, the study assessed the degree of skewness of individual PVTs and PVT intercorrelations for the overall sample and by validity group.

Method: Participants were 283 adult neuropsychology outpatients evaluated at an academic medical center. Participants were initially classified as having valid (≤1 PVT failure; n = 225) or invalid (≥2 PVT failures; n = 58; base rate of 20% performance invalidity) performance based on four independent criterion PVTs. Failure rates of 10 additional PVTs were then compared, and sensitivity and specificity were calculated at different thresholds (e.g. ≥1, ≥2, ≥3, ≥4 PVT failures) to determine the optimal threshold for detecting invalid performance while maintaining ≥ 90% specificity.

Results: Findings indicate that failing ≥ 2 PVTs yielded 86% sensitivity/76% specificity, failing ≥ 3 PVTs yielded 69% sensitivity/92% specificity, failing ≥ 4 PVTs yielded 57% sensitivity/96% specificity, failing ≥ 5 PVTs yielded 29% sensitivity/99% specificity, and failing ≥ 6 PVTs yielded 22% sensitivity/100% specificity. PVT intercorrelations were generally small for the overall sample and by validity group. As expected, data were more highly skewed for patients with valid performance.

Conclusions: Findings were consistent with previous research and demonstrate that the three-failure threshold optimally detects invalid performance when 10 PVTs are administered. These findings inform the use of multiple PVTs in clinical settings and aid in the interpretation of PVT results.