The Bayley-III scale underestimates developmental delay in extremely premature and extremely low birth weight infants

Article Outline

• Question
• Design
• Setting
• Participants
• Intervention
• Outcomes
• Main Results
• Conclusions
• Commentary
• Copyright

Anderson PJ, De Luca CR, Hutchinson E, Roberts G, Doyle LW, and the Victorian Infant Collaborative Group. Underestimation of developmental delay by the new Bayley-III scale. Arch Pediatr Adolesc Med 2010;164:352-6.

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Question 

Among 2-year-old children who were extremely preterm and those carried to term, can the Bayley Scales of Infant and Toddler Development (Bayley-III) accurately detect developmental delay?

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Design 

Prospective cohort study.

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Setting 

The state of Victoria, Australia.

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Participants 

Consecutive surviving children (n = 221) who were born either at less than 28 weeks' gestational age (extremely preterm [EP]) or with less than 1000 g birth weight (extremely low birth weight [ELBW]) in the state of Victoria, Australia, in 2005 and randomly selected controls (n = 220)who were both carried to term and of normal birth weight.

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Intervention 

Development was assessed in survivors at 2 years of age, corrected for prematurity, using the Bayley-III scale. Children were also assessed for neurosensory impairments by blinded pediatricians.

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Outcomes 

Developmental delay was calculated according to both (1) the Bayley-III norms; and (2) the control group mean (standard deviation [SD]) and these results were compared.

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Main Results 

Follow-up rates of both cohorts were high (>92%). Mean values for all composite and subtest scores for the EP/ELBW group were significantly below those of the control group (P < .001), with the magnitude of all group differences being in excess of two-thirds SD. Mean values for the EP/ELBW group approached the normative mean, but in contrast, the mean values for the control group were higher than expected, with composite scores being between 0.55 and 1.23 SD above the normative mean. Proportions of children with developmental delay were grossly underestimated using the reference values, but were within the expected range when computed relative to the mean (SD) for the controls.

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Conclusions 

The Bayley-III scale seriously underestimates developmental delay in 2-year-old Australian children.

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Commentary 

This important study examines the use of the Bayley-III developmental assessments among 221 EP/ELBW survivors at age 2 years born in 2005 in Victoria, Australia. If one uses the Bayley-III normative tables, then the performance of these EP survivors is most reassuring. Only 8% of Australian EP survivors at 2 years experience cognitive disability (IQ<70) compared with 29% of US survivors at 18 months. However, if one uses the full-term Australian group for comparison, an important strength of this study, then the bar for being “average” is set higher. Then, the Melbourne EP survivors score 12-18 standard points below the mean. This study forces pediatricians to address the goals of developmental surveillance after EP/ELBW. If the goal is to detect those children who are in need of additional developmental supports because of motor, communicative, and cognitive delays, then using the Bayley-III without concurrent controls will result in many vulnerable children not meeting eligibility criteria for early intervention in many regions of the United States. This will be extremely deleterious to children with social disadvantage, as their term peers already struggle with high rates of entering kindergarten with challenges in communicative, perceptual, executive function, and cognitive skills.