Psychometric Properties of the Preschool Language Scales, Fifth Edition (PLS-5) in Russian-Speaking Children: A Classical and Item Response Theory Study

Difficulties in language development are common hallmarks of different neuro-developmental disorders. Early diagnosis is a crucial factor for proper early interventions and better prognosis. Currently, there is a severe shortage of standardized instruments for assessing potential language disorders in Russia. To address this gap, we analyzed the psychometric properties of the Russian version of the Preschool Language Scale, 5th edition (RPLS-5). The sample consisted of 473 children aged 3 to 96 months (Mean=32.64, SD=19.79), including 224 typically developing (TD) children and 240 at-risk (AR) children. To assess the reliability of the Russian version of the PLS-5, we used both Classical Test Theory (CTT) and Item Response Theory (IRT). The results indicated the high reliability of the RPLS-5 based on both types of analyses. According to the results of IRT analysis, the difficulty of items ranged from very easy to very difficult, and with few exceptions, the difficulty parameters consistently increased for each subsequent item, reflecting the hierarchical organization of the test. The discrimination parameters ranged from high to perfect. In general, IRT demonstrated that the RPLS-5 is reliable for low-to-high levels of language abilities