The stability of the diagnosis of developmental disability between ages 2 and 8 in a geographic cohort of very preterm children born in 1997

Objective: Studies reporting the developmental outcomes for very preterm (VPT) children often focus on development at age 2 years. The aim of this study was to assess the stability of the rates of diagnosis of developmental disability from age 2 to 8 years in a regional cohort of VPT and extremely low-birth weight (ELBW) children and compare these with term controls. Methods: VPT (22-27 completed weeks of gestation) and ELBW (birth weight 500-999 g) children and matched term controls born in Victoria, Australia, in 1997 were enrolled at birth in a regional prospective longitudinal study. Outcomes were assessed at ages 2 and 8 years. Results: Of the 283 VPT/ELBW live births, 71% survived to age 8 years and 94% were assessed. Of the 199 controls, 100% survived to age 8 years and 86.9% were assessed. At age 2 years, the rates of nil, mild, moderate and severe disabilities in the VPT/ELBW children were respectively 51.9%, 20.9%, 13.4% and 13.9%; and at age 8 years, 43.9%, 36.9%, 10.7% and 8.6%. The Cohen κ statistic revealed poor agreement between disability status at ages 2 and 8 years for VPT/ELBW children (0.20, p<0.001) but a higher level of agreement (0.37, p<0.001) for the control children. This was primarily driven by differences in classification of cognitive disability between ages 2 and 8 years. Conclusions: Developmental outcomes at age 2 years are only a moderate predictor of long-term outcome and are not a reliable end point for follow-up studies of VPT and ELBW children.