Digit Span embedded validity indicators in neurologically-intact veterans

Abstract

Abstract Objective: Embedded validity measures are useful in neuropsychological evaluations but should be updated with new test versions and validated across various samples. This study evaluated Wechsler Adult Intelligence Scale, 4th edition (WAIS-IV) Digit Span validity indicators in post-deployment veterans. Method: Neurologically-intact veterans completed structured diagnostic interviews, the WAIS-IV, the Medical Symptom Validity Test (MSVT), and the b Test as part of a larger study. The Noncredible group included individuals who failed either the MSVT or the b Test. Of the total sample (N = 275), 21.09% failed the MSVT and/or b Test. Diagnostic accuracy was calculated predicting group status across cutoff scores on two Digit Span variables, four Reliable Digit Span (RDS) variables, and two Vocabulary minus Digit Span variables. Results: Digit Span age-corrected scaled score (ACSS) had the highest AUC (.648) of all measures assessed; however, sensitivity at the best cutoff of <7 was only 0.17. Of RDS measures, the Working Memory RDS resulted in the highest AUC (.629), but Enhanced RDS and Alternate RDS produced the highest sensitivities (0.22). Overall, cutoff scores were consistent with other studies, but sensitivities were lower. Vocabulary minus Digit Span measures were not significant. Conclusions: Digit Span ACSS was the strongest predictor of noncredible performance, and outperformed traditional RDS variants. Sensitivity across all validity indicators was low in this research sample, though cutoff scores were congruent with previous research. Although embedded Digit Span validity indicators may be useful, they are not sufficient to replace standalone performance validity tests.