Utility of the WASI–II 2-Subtest Full Scale IQ for Identifying Impaired Cognitive Functions

This study focused on how accurately the WASI–II 2FSIQ predicts the 4FSIQ. If two subtests can identify intellectual disability, a low score might prompt a switch to the WAIS–IV or WISC–V prior to completing the four WASI–II subtests. Participants were 94 individuals with psychiatric or neurological disorders (age M = 49.04 yrs, education M = 13.48 yrs) seem for clinical evaluation. The correlation between the 2FSIQs and 4FSIQs in the total sample was high, r(92) = .96, p < .001, but the former cannot be relied upon to predict 4FSIQs. It overestimated 4FSIQs in 69.1% of the cases, with only 50% of the 2FSIQs falling within + 3 points of the 4FSIQs. However, classification accuracy statistics indicated that the 2FSIQ effectively screened for the presence of intellectual disability. A 2FSIQ standard score cutoff of ≤ 79 yielded a high probability that the 4FSIQ was also at or below the cut score.