The use of the Bayley Scales of Infant and Toddler Development III with clinical populations: a preliminary exploration.

In response to concerns that the Bayley Scales of Infant and Toddler Development III (BSIDIII) underestimate delay in clinical populations, this study explores developmental quotient scores as an alternative to composite scores for these children. One hundred and twenty-two children aged ≤42 months, referred for diagnosis of developmental disability from January 2007 to May 2010, were assessed, and their composite and developmental quotient scores on each scale were compared. Composite scores identified only 22% (cognitive), 27% (motor), and 47.5% (language) of children as having a developmental disability. Developmental quotient scores were significantly lower than composite scores, giving rates of developmental disability of 56.6% (cognitive), 48.4% (motor), and 74.6% (language) and more closely matching both clinical impressions of delay and the proportions of those children who were also delayed on standardized tests of adaptive function.