This study evaluated the clinical utility of two embedded performance validity tests (PVTs) developed for the Repeatable Battery for the Assessment of Neuropsychological Status: the Effort Index (EI) and the Effort Scale (ES) in mild traumatic brain injury (TBI) patients. Participants were 250 military service members (94.0% male; Age: M = 28.4, SD = 7.6) evaluated following mild TBI on average 7.4 months (SD = 15.6) post-injury. Participants were divided into two groups based on their performance on the Test of Memory Malingering: PVT-Pass, n = 193; PVT-Fail, n = 57. For the EI, recommended cut-offs for extremely probable, highly probable, and probable poor effort were established. A cut-off score of >3 resulted in low sensitivity (.14), high specificity (.99) and positive predictive power (.94), and moderate negative predictive power (.68) and is recommended for identifying highly probable poor effort. For both the EI and ES, cut-offs for probable poor effort were identified; however, classification accuracy was not much improved relative to simply using the sum of the List Recognition and Digit Span raw scores to classify poor effort. It is acknowledged that the use of a different criterion would likely have resulted in different findings. Nevertheless, findings support the use of the EI and the ES as a "red flag" for possible poor effort in mild TBI patients, but suggest that, in most cases, additional PVTs would be required to accurately rule poor effort in or out.
Keywords: Effort; mild traumatic brain injury; performance validity; repeatable battery for the assessment of neuropsychological status; response bias.