Utility of two new embedded measures of performance validity for the Wisconsin Card Sorting Test-64

Objective: We sought to determine the utility of two new embedded validity indices for the Wisconsin Card Sorting Test-64 (Henry, 2024; Kosky et al., 2022). The goal was to determine if these proposed indices would be associated with specificity ≥ .90, sensitivity ≥ .40, and positive likelihood ratio of ≥ 2, in a clinical traumatic brain injury (TBI) sample with a broad range of injury severity. Method: We used logistic regression to investigate how well each new index could distinguish performance validity classification of 173 persons with TBI who were evaluated within 1-36 months after injury. Participants were classified based on at least two independent performance validity tests as having provided valid performance (n = 146) or invalid performance (n = 27). Results: Both indices had acceptable Likelihood Ratios. The Kosky et al. index had suboptimal sensitivity and specificity, while the Henry index had acceptable sensitivity (.41) and better specificity (.88). However, when either index, considered in isolation or combined, indicated invalid performance, it was most often a false positive. Conclusion: Kosky et al.'s index did not meet the a priori criteria. While the Henry index was more robust, more than half (18/29) of the cases it identified as invalid were false positives. Differences in base rates between the original sample of Henry and the current one likely affected positive predictive power of the new index. Results suggest that this index is more useful to rule out invalid performance than to rule it in.