Is the Bayley screening test norms appropriate for Persian language children?

To evaluate the distribution of the Bayley screening test scores by age, in Persian children and compare developmental risk categories distributions between Persian and reference norms.
A representative sample of 417, 1 to 42-months-old, typically developing children by consecutive sampling from health -care centers recruited, during the 2014 to 2015 in Tehran city. The Bayley measures children’s cognitive, receptive and expressive communication, fine and gross motor skills. For determining cut points for the subtest scores, two cuts points were determined for each age group, dividing scores into the three bands that identify the at risk, emerging (between the 2nd and 25th percentiles), and competent categories. We estimated the agreement between the distributions of the risk categories between the two samples using weighted kappa statistics.
The comparison of neurodevelopmental classification of children based on two norms determined that; approximately 70-80% of all tests administered to the participating children were classified as normal by both norms. Weighted kappa coefficients for the five subtests ranged from 0.56 to 0.89 suggesting moderate agreement between the classification using the reference and Persian norms. Expressive and receptive communication subtests had the lowest kappa scores (0.56 and 0.59, respectively), and classification of gross motor demonstrated the highest level of agreement (0.89).
Our findings demonstrate that reliance on reference -based norms for the Bayley test in Persian children results in misclassification of developmental delay.