Performance validity of the Dot Counting Test in a dementia clinic setting

Abstract

Objective This study examined the utility of a performance validity test (PVT), the Dot Counting Test (DCT), in individuals undergoing neuropsychological evaluations for dementia. We investigated specificity rates of the DCT Effort Index score (E-Score) and various individual DCT scores (based on completion time/errors) to further establish appropriate cutoff scores. Method This cross-sectional study included 56 non-litigating, validly performing older adults with no/minimal, mild, or major cognitive impairment. Cutoffs associated with ≥90% specificity were established for 7 DCT scoring methods across impairment severity subgroups. Results Performance on 5 of 7 DCT scoring methods significantly differed based on impairment severity. Overall, more severely impaired participants had significantly higher E-Scores and longer completion times but demonstrated comparable errors to their less impaired counterparts. Contrary to the previously established E-Score cutoff of ≥17, a cutoff of ≥22 was required to maintain adequate specificity in our total sample, with significantly higher adjustments required in the Mild and Major Neurocognitive Disorder subgroups (≥27 and ≥40, respectively). A cutoff of >3 errors achieved adequate specificity in our sample, suggesting that error scores may produce lower false positive rates than E-Scores and completion time scores, both of which overemphasize speed and could inadvertently penalize more severely impaired individuals. Conclusions In a dementia clinic setting, error scores on the DCT may have greater utility in detecting non-credible performance than E-Scores and completion time scores, particularly among more severely impaired individuals. Future research should establish and cross-validate the sensitivity and specificity of the DCT for assessing performance validity.