Differentiating Developmental Outcome between Infants with Severe Disability in Research Studies: The Role of Bayley Developmental Quotients

ObjectivesTo investigate whether infants with a score <50 on the Bayley Scales of Infant Development, Second Edition (BSID-II) demonstrated differences in functional ability, and to assess whether the Bayley Developmental Quotients (DQs) indicated such differences.Study designPreterm infants (n = 67; 47 boys) with posthemorrhagic ventricular dilatation were evaluated at 25 months past term age using the BSID-II and grading of functional ability. Mental and Motor Bayley DQs were derived and compared with functional ability.ResultsAmong the 34 subjects (51%) with a BSID-II score <50, there were clinically significant differences in the ability to walk, sit, eat, speak, and see. In all subjects, there were significant differences in Mental and Motor Bayley DQs based on grade of disability in each domain except hearing.ConclusionsBayley DQ quantified the spread of functional ability in all children, provided a continuous parameter to compare ability in severely delayed children, and should be considered in future therapeutic trials of infants with brain injury.