Investigating the interchangeability and diagnostic utility of the PPVT-III and PPVT-IV for children with and without SLI

The receptive vocabulary performance of pre-school children with specific language impairment (SLI) and typically-developing (TD) controls was compared on the Peabody Picture Vocabulary Test third and fourth edition (PPVT-III and PPVT-IV) to determine consistency in performance and the effect of test revision on identification of impairment. Participants included 40 pre-school children with SLI and 40 controls. Tests were administered in counterbalanced order. Despite a strong relationship between performance on these two tests (p < 0.001), 35% of children performed differently between the two test versions. Children with SLI performed significantly worse than TD children on both tests (p < 0.001). Discriminate analyses identified an optimal standard score cut-off of 103 for both tests. Using this cut-off, sensitivity remained consistent at 80% (95% CI = 0.64-0.90), while specificity was 75% (95% CI = 0.59-0.87) on the PPVT-III and 70% (95% CI = 0.53-0.83) on the PPVT-IV. The results suggest that the two tests do not appear to be interchangeable for more than 1/3rd of children. The findings also highlight the misperception that newer test versions are superior to older in identifying presence or absence of language impairment. Children with SLI are unlikely to score low on these commonly used receptive vocabulary tests, despite known deficits of children with SLI in the area of vocabulary acquisition. Possible explanations for why children with SLI score well on these types of tests will be discussed.