An exploration into response validity

Objectives: Performance validity tests (PVTs) and symptom validity tests (SVTs) have been recommended by the British Psychological Society to assist clinicians in validating assessment data. The current study aimed to explore the base rate of PVT failure in an NHS neuropsychology service, a setting relatively unexplored. A secondary aim was to investigate the relationship between PVT and SVT performance. Lastly, group differences in those passing and failing PVTs were explored in terms of demographics, and psychological functioning.

Method: Archival test data (n=127) was drawn from an NHS outpatient neuropsychology service. Participants completed one stand-alone PVT (the Test of Memory Malingering [TOMM]), one embedded PVT (Digit Span age-corrected scaled score [DS-SS]), and one SVT (the Personality Assessment Inventory [PAI]).

Results: The base rate of failure on any one PVT was 26%. The rate of TOMM failure was 12% and 6% additionally failed an embedded PVT. A significant relationship was found between PVT and SVT performance. Significantly elevated Paranoia, Anxiety-Related Disorders, and Schizophrenia PAI scales, as well as lower Full Scale IQ scores, were found in those who failed PVTs compared to those who passed. No other group differences on demographics were found, including reported financial incentive.

Conclusions: Findings suggest that PVT failure occurs in a sizable minority of NHS ABI outpatients, which is unlikely to be simply explained by malingering for material gain. Elevations in reported psychopathological symptoms may be related to emotional and cognitive sequalae resulting from the ABI itself. Careful interpretation of neuropsychological test data is endorsed.