Validity and Reliability of a Language Development Scale for Persian-speaking Children Aged 2-6 Years

Background: Language disorders may affect receptive and/or expressive language skills. The use of a validated and reliable assessment tool is essential to assess these skills in children. The present study aimed to develop a valid and reliable language development instrument for Persian-speaking children aged 2-6 years. Methods: The present cross-sectional study was conducted during 2016-2017 in three main Iranian cities, namely Mashhad, Tehran, and Isfahan. The target population was children between the ages of 2 and 6 in various kindergartens and schools. The Persian Language Development Scale (PLDS) was developed by incorporating linguistic characteristics of the Persian language and Iranian culture. Following a number of iterations, including a pilot study of 36 children, the final version of the PLDS tool was used to assess the receptive and expressive language skills of 460 children. The reliability and validity of the PLDS tool were examined. Results: The content validity ratio (CRV) of the PLDS tool was 0.85. The tool could differentiate children by age, but not by sex. The test-retest reliability, with 10 days interval, showed a significant correlation between the coefficients of receptive (0.96) and expressive (0.93) scales. The intraclass correlation coefficient (ICC) for receptive and expressive scales was 0.93 and 0.98, respectively. The internal consistency, using the KR-21, for the receptive and expressive scales was 0.88 and 0.92, respectively. Conclusion: A language development scale has been developed to assess receptive and expressive language skills in Iranian children aged 2-6 years. The validity and reliability of the tool were confirmed.