If Invalid PVT Scores Are Obtained, Can Valid Neuropsychological Profiles Be Believed?

Background: Performance Validity Testing (PVT) decision-making rules may be indeterminate in patients with neurological disease in which PVT characteristics have not been adequately studied. We report a patient with multiple sclerosis (MS) who failed computerized PVT testing but had normal memory scores with a neuropsychological profile consistent with expected MS disease-related weaknesses. Method: Neuropsychological testing was conducted on two occasions in a middle-aged woman with an established MS diagnosis to address concerns of possible memory decline. Testing was discontinued after PVT scores below recommended cut-points were obtained during the first evaluation. During the second assessment, subthreshold PVT scores on a different computerized PVT were obtained, but unlike the first assessment, the entire neuropsychological protocol was administered. Results: Despite subthreshold computerized PVT scores, normal learning and memory performance was obtained providing objective data to answer the referral question. Other neuropsychological findings included decreased processing speed, poor working memory, and poor executive function consistent with her MS diagnosis. Embedded PVT scores were normal. Conclusions: We speculate that poor computerized PVT scores resulted from the disease-related features of MS, although we also discuss approaches to reconcile apparently contradictory PVT versus neuropsychological results if the contributions of disease-related variables on PVTs scores are discounted. This case demonstrates the value of completing the assessment protocol despite obtaining PVT scores below publisher recommended cutoffs in clinical evaluations. If subthreshold PVT scores are considered evidence of performance invalidity, it is still necessary to have an approach for interpreting seemingly credible neuropsychological test results rather than simply dismissing them as invalid.