Instability of delay classification and determination of early intervention eligibility in the first two years of life.

The purpose of this study was to determine the effectiveness of the Bayley Scales of Infant Development, Third Edition (Bayley-III) to track development and classify delays in low- and high-risk infants across the first two years of life. We assessed cognitive, language, and motor development in 24 low-risk full-term and 30 high-risk preterm infants via seven assessments performed between 3 and 24 months corrected age. The Bayley-III resulted in highly unstable delay classifications, low sensitivities, and poor positive predictive values across time. The results highlight that early intervention professionals, researchers, and policy makers should: (1) emphasize clinical opinion and prevalence of risk factors rather than standardized assessment findings when classifying delays and determining eligibility for services, and (2) develop more effective developmental assessments for infants and young children.