Base Rates of Invalid Test Performance Across Clinical Non-forensic Contexts and Settings

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Abstract
Objective: Base rates of invalidity in forensic neuropsychological contexts are well explored and believed to approximate 40%, whereas base rates of invalidity across clinical non-forensic contexts are relatively less known. Methods: Adult-focused neuropsychologists (n = 178) were surveyed regarding base rates of invalidity across various clinical non-forensic contexts and practice settings. Median values were calculated and compared across contexts and settings. Results: The median estimated base rate of invalidity across clinical non-forensic evaluations was 15%. When examining specific clinical contexts and settings, base rate estimates varied from 5% to 50%. Patients with medically unexplained symptoms (50%), external incentives (25%–40%), and oppositional attitudes toward testing (37.5%) were reported to have the highest base rates of invalidity. Patients with psychiatric illness, patients evaluated for attention deficit hyperactivity disorder, and patients with a history of mild traumatic brain injury were also reported to invalidate testing at relatively high base rates (approximately 20%). Conversely, patients presenting for dementia evaluation and patients with none of the previously mentioned histories and for whom invalid testing was unanticipated were estimated to produce invalid testing in only 5% of cases. Regarding practice setting, Veterans Affairs providers reported base rates of invalidity to be nearly twice that of any other clinical settings. Conclusions: Non-forensic clinical patients presenting with medically unexplained symptoms, external incentives, or oppositional attitudes are reported to invalidate testing at base rates similar to that of forensic examinees. The impact of context-specific base rates on the clinical evaluation of invalidity is discussed.

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