Using the Bayley-III to assess neurodevelopmental delay: which cut-off should be used?
BACKGROUND
As the latest edition of the Bayley Scales (Bayley-III) produces higher scores than its predecessor (BSID-II), there is uncertainty about how to classify moderate-severe neurodevelopmental delay. We have investigated agreement between classifications of delay made using the BSID-II and Bayley-III.


METHODS
BSID-II Mental Development Index (MDI) and Bayley-III cognitive and language scales were administered in 185 extremely preterm (<27 wk) children. A combined Bayley-III score (CB-III) was computed. Agreement between delay classified using MDI scores <70 and various Bayley-III cut-offs was assessed.


RESULTS
Bayley-III cognitive and language scores were close to the normative mean and were higher than BSID-II MDI scores. Nineteen (10.2%) children had MDI <70. Bayley-III scores <70 significantly underestimated the proportion with MDI <70. Bayley-III cognitive and language scores <85 had 99% agreement with MDI <70 and underestimated delay by 1.1%. CB-III scores <80 had 98% agreement and produced the same proportion with delay.


CONCLUSIONS
Bayley-III cognitive and language scores <85 or CB-III scores <80 provide the best definition of moderate-severe neurodevelopmental delay for equivalence with MDI <70. CB-III scores have the advantage of producing a single continuous outcome measure but require further validation. The relative accuracy of both tests for predicting long-term outcomes requires investigation.
Department of Health Sciences, University of Leicester, Leicester, UK.
Samantha
S
Johnson
Research Department of Academic Neonatology, Institute for Women's Health, University College London, London, UK.
Tamanna
T
Moore
Research Department of Academic Neonatology, Institute for Women's Health, University College London, London, UK.
Neil
N
Marlow
D002657:Child Development; D002675:Child, Preschool; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis; D002658:Developmental Disabilities / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007234:Infant, Premature; D007806:Language Disorders / Q000175:diagnosis; D008297:Male; D009483:Neuropsychological Tests / Q000592:standards*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome