Performance validity measures in clinical patients with aphasia.

Introduction: Performance validity testing has developed into an indispensible element of neuropsychological assessment, mostly applied in forensic determinations. Its aim is to distinguish genuine patient performance from invalid test profiles. Limits to the applicability of performance validity tests (PVTs) may arise when genuine cognitive symptoms are present.

Method: We studied the robustness of four commonly used PVTs in a sample of 15 acute patients after cerebrovascular stroke, with first manifestations of aphasia. Severity of aphasia varied from very mild to severe. Subsequent neuroimaging revealed left-hemisphere infarction for all participants.

Results: The Test of Memory Malingering was the only measure found to be robust against effects of genuine language impairment (one positive on Trials 1 and 2, none on Trial 3), while unacceptable false-positive rates were found for the Fifteen-Item Test (60%) and two embedded measures, Reliable Spatial Span (40%) and Reliable Digit Span (73.3%). Four patients (26.7%) scored positive on at least three of the four PVTs.

Conclusions: These data add to the ongoing discussion about the risk of false-positive classifications in genuine patient populations. Misdiagnosis with severe consequences for the patient in question may arise if results of PVTs are interpreted without concurrently considering the whole context of clinical evidence.