Performance Validity Tests in non-litigant patients with Functional Motor Disorders

Background: Performance Validity Tests (PVTs) are used in neuropsychological assessments to detect patterns of performance suggesting that the broader evaluation may be an invalid reflection of an individual's abilities. Data on Functional motor disorder (FMD) are currently poor and conflicting. Objectives: We aimed to examine the rate of failure at three different PVTs of non-litigant, non-compensation seeking FMD patients, and we compared their performance to that of healthy controls and controls asked to simulate malingering (healthy simulators). Methods: We enrolled 29 non-litigant, non-compensation seeking patients with a clinical diagnosis of FMD, 29 healthy controls and 29 healthy simulators. Three PVTs, the Coin in the Hand Test (CIH), the Rey 15-item Test (REY) and the Finger Tapping Test (FTT), were employed. Results: FMD Patients showed low rates of failure at the CIH and REY tests (7% and 10%, respectively) and slightly higher at the FTT (15%, n=26) test, which implies a motor task. Their performance was statistically comparable to that of healthy controls but statistically different from that of healthy simulators (p<0.001). 93% of FMD patients, 7% of healthy simulators, and 100% of healthy controls passed at least two of the three tests. Conclusions: PVT performance of non-litigant, non-compensation seeking patients with FMD ranged from 7 to 15%. Patient's performance was comparable to controls and significantly differed from that of simulators. This simple battery of three PVTs could be of practical utility and routinely used in clinical practice.