Standardization of the Bayley scales of Infant and toddler Development for Iranian children

Objective: The children develop in several domains, including motor, cognitive, communication and social-emotional. The first few years of life are particularly important because vital development occurs in all domains. Early detection of developmental delays is essential in planning for early intervention. The aim of this study was to standardization  of the Bayley scales of infant development  in 1- 42 months old Iranian children. Materials & methods: The standardization sample for this study included 1700 children divided into 17 age groups. Each age group was composed of 100 participants. The normative information was based on a national sample representative of the Iran population for infants 1 through 42 months old in Iran Statistical Center. For each age group, the total raw scores of each scale including; cognitive, receptive and expressive communication, fine and gross motor, were converted to scaled scores with a mean of 10 and a standard deviation (SD) of 3. The composite scores (cognitive, language and motor) derived from sums of scales scaled scores. The composite scores are scaled to a metric with a mean of 100 and a SD of 15, and range from 40-160. Growth scores (range from 200-800, with a mean of 500 and a SD of 100), percentile ranks (range from 1-99, with 50 as the mean and median) and developmental age equivalent determind. Confidence intervals for all five scales and the relevant curves were drawn. In order to compare the level of development of the United State (normative sample) and Iranian children, their mean raw scores in five scales were compaired for difference in scores. Results: The Bayley was performed on 1744 children aged 0-42 months. The number of girls and boys were 908 (52.1%) and 836 (47.9%) respectively. Comparing the level of development of Iranian children with the US sample, the mean scores in 28 age groups were different (Pvalue<0.05). In seven age/scale, the US scores were higher than in Iranian sample (less than 6 months age band), and  in 21 age/scale, the scores of Iranian sample were higher than the US (above 6 months age band). Conclusion: In order to early detection and intervention of children with developmental delay, normalized test should be used in Iran. Using the US norms in Iranian children leads to inaccuracy in early detection of children with developmental delay.