Utility of various WAIS-IV Digit Span indices for identifying noncredible performance validity among cognitively impaired and unimpaired examinees

Objective: Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Reliable Digit Span (RDS), RDS-revised (RDS-R), and age-corrected scaled score (ACSS) are validated and commonly used embedded performance validity tests (PVTs), though existing validation studies have largely examined younger (approximate ages 19-35) patients with mild traumatic brain injury or those without cognitive impairment. This study compared the classification accuracy of RDS, RDS-R, and ACSS in a mixed clinical sample of relatively older (M age = 54.61) veterans with and without neurocognitive impairment.

Method: During a comprehensive neuropsychological evaluation, 113 clinically-referred veterans completed the WAIS-IV Digit Span subtest and the following criterion PVTs: Dot Counting Test, Word Choice Test, and Test of Memory Malingering. Those with ≤1 criterion PVT failure were classified as valid (n = 87), whereas those with ≥2 failures were classified as noncredible (n = 26). Among valid participants, 49% were cognitively impaired.

Results: RDS, RDS-R, and ACSS all significantly predicted validity group membership with respective areas under the curve (AUCs) of .79, .81, and .85, and optimal cut scores of RDS ≤ 5, RDS-R ≤ 9, and ACSS ≤ 5. Lower accuracy and AUCs were observed for the valid-cognitively impaired subsample across indices, but to a greater degree for traditional RDS. ACSS evidenced maximal sensitivity/specificity for the total sample (≤5; .62/.87), cognitively unimpaired subsample (≤5; .62/.95), and cognitively impaired subsample (≤4; .39/.86).

Conclusions: ACSS yielded better classification accuracy and sensitivity/specificity than RDS and RDS-R. While all three indices have utility as embedded PVTs, ACSS ≤ 5 may be most robust to cognitive impairment while identifying noncredible performance.