An abbreviated WISC-5 model for identifying youth at risk for intellectual disability in a mixed clinical sample

Objective: The correct “dosing” of neuropsychological assessment is of interest for the purposes of cost management and the personalization of medicine/assessment. In this context, embedded IQ screening, rather than routine comprehensive IQ testing, may be useful in identifying youth at risk for Intellectual Disability (ID) for whom further assessment is needed. This retrospective, cross-sectional study examined subtests from the Wechsler Intelligence Scale for Children-Fifth Edition (WISC-5) needed to identify youth with Full Scale IQ (FSIQ) ≤75. Method: Data were obtained from a large pediatric clinically referred sample (N = 4,299; Mean Age = 10.7 years; Range = 6-16y; 66% male; 54% White; 29% receiving Public Insurance), divided into training (n = 2149) and test (n = 2150) samples. Results: In the training sample, sequential and additive regression-based models for predicting FSIQ comprised of one (Block Design [BD]), two (BD + Similarities [SI]), three (BD + SI + Matrix Reasoning [MR]), and four (BD + SI + MR + Digit Span [DS]) subtests of the WISC-5 explained 61.3%, 82.7%, 88.5%, and 93.0% of FSIQ variance, respectively. Using a predicted FSIQ ≤ 80 as a cut score to identify persons with observed FSIQ ≤75, the two subtest (BD + SI) model showed strong sensitivity (83.4), specificity (90.5), and negative predictive value (96.2) in the test sample; however, positive predictive value was low (65.3%). Three and four subtest models provided incremental, but modest gains in classification metrics. Conclusions: Findings suggest the first several subtests of the WISC-5 can be used to identify clinically referred youth at risk for ID who subsequently require full administration of the WISC-5 for consideration of an ID diagnosis.