Which Bayley-III cut-off values should be used in different developmental levels?

BACKGROUND/AIM: Latest version of Bayley Scales (Bayley-III) and its predecessor (BSID-II) are the most widely used standardized developmental tools in infancy and early childhood. Recent studies showed that Bayley-III scores were higher than BSID-II in 18–24 month-old and mostly premature infants. We aimed to evaluate the generalization of inflated scores of Bayley-III to children aged 6–42 months with different disease groups, and to find out which cut-off points should be used in Bayley-III to detect mild, moderate, and severe developmental delay according to BSID-II standard cut-off points. MATERIALS AND METHODS: Two hundred and fifty-five children aged 6–42 months with different diseases and developmental levels were administered both the Bayley-III and BSID-II in the same session between 15 November 2017 and 15 April 2018. RESULTS: The mean Bayley-III Cognitive Composite (CC) and Cognitive Language Composite (CLC) scores were respectively 13.1 ± 9.1 and 8.6 ± 8 points higher than BSID-II Mental Development Index (MDI) scores (P < 0.001). The mean Bayley-III Motor Composite (MC) scores were 14.4 ± 10.5 points higher than BSID-II Psychomotor Developmental Index (PDI) scores (P < 0.001). Cognitive delay was found in 126 (49.4%) and 59 (23.1%) children according to BSID-II MDI and Bayley-III CC scores, respectively. Motor delay was found in 174 (69.3%) and 86 (34.3%) children according to the BSID-II PDI and Bayley-III MC scores, respectively. Children had less cognitive (48.6%) and motor delay (54.5%) according to Bayley-III scores. Bayley-III scores were significantly higher than BSID-II scores for all ages (P < 0.001). According to ROC analysis the cut-off scores for mild, moderate, and severe delay were 92.5, 83.2, and 71.2 for Bayley-III CLC; and 98.5, 86.5, and 74.5 for Bayley-III MC, respectively. CONCLUSION: Bayley-III scores should be interpreted carefully for all age ranges and different diagnosis. The risk for underestimation of developmental delays by Bayley-III should be kept in mind. Different Bayley-III cut-off scores should be used to define developmental delay levels.