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. CONCLUSION: 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.

Neurological and developmental outcome in extremely preterm children born in England in 1995 and 2006: the EPICure studies.

OBJECTIVE: To determine outcomes at age 3 years in babies born before 27 completed weeks' gestation in 2006, and to evaluate changes in outcome since 1995 for babies born between 22 and 25 weeks' gestation. DESIGN: Prospective national cohort studies, EPICure and EPICure 2. SETTING: Hospital and home based evaluations, England. PARTICIPANTS: 1031 surviving babies born in 2006 before 27 completed weeks' gestation. Outcomes for 584 babies born at 22-25 weeks' gestation were compared with those of 260 surviving babies of the same gestational age born in 1995. MAIN OUTCOME MEASURES: Survival to age 3 years, impairment (2008 consensus definitions), and developmental scores. Multiple imputation was used to account for the high proportion of missing data in the 2006 cohort. RESULTS: Of the 576 babies evaluated after birth in 2006, 13.4% (n=77) were categorised as having severe impairment and 11.8% (n=68) moderate impairment. The prevalence of neurodevelopmental impairment was significantly associated with length of gestation, with greater impairment as gestational age decreased: 45% at 22-23 weeks, 30% at 24 weeks, 25% at 25 weeks, and 20% at 26 weeks (P<0.001). Cerebral palsy was present in 83 (14%) survivors. Mean developmental quotients were lower than those of the general population (normal values 100 (SD 15)) and showed a direct relation with gestational age: 80 (SD 21) at 22-23 weeks, 87 (19) at 24 weeks, 88 (19) at 25 weeks, and 91 (18) at 26 weeks. These results did not differ significantly after imputation. Comparing imputed outcomes between the 2006 and 1995 cohorts, the proportion of survivors born between 22 and 25 weeks' gestation with severe disability, using 1995 definitions, was 18% (95% confidence interval 14% to 24%) in 1995 and 19% (14% to 23%) in 2006. Fewer survivors had shunted hydrocephalus or seizures. Survival of babies admitted for neonatal care increased from 39% (35% to 43%) in 1995 to 52% (49% to 55%) in 2006, an increase of 13% (8% to 18%), and survival without disability increased from 23% (20% to 26%) in 1995 to 34% (31% to 37%) in 2006, an increase of 11% (6% to 16%). CONCLUSION: Survival and impairment in early childhood are both closely related to gestational age for babies born at less than 27 weeks' gestation. Using multiple imputation to account for the high proportion of missing values, a higher proportion of babies admitted for neonatal care now survive without disability, particularly those born at gestational ages 24 and 25 weeks.

Screening for autism in extremely preterm infants: problems in interpretation.

AIM: The aim of this article was to report the prevalence of, and risk factors for, positive autism screens using the Modified Checklist for Autism in Toddlers (M-CHAT) in children born extremely preterm in England. METHOD: All children born at not more than 26 weeks' gestational age in England during 2006 were recruited to the EPICure-2 study. At 2 years of age, postal questionnaires incorporating the M-CHAT and additional developmental questions were sent to the parents of each survivor (n=1031; 499 male, 532 female), of which 523 (266 male, 257 female; 51%) were returned completed. RESULTS: The prevalence of positive M-CHAT screens in this extremely preterm population was 41% (216/523; 130 male; 86 female). Severe bronchopulmonary dysplasia, administration of postnatal steroids, late-onset bacteraemia, and being male were statistically significantly associated with a positive screen. Coexisting disabilities were present in 320 (62%) children. Of 200 children without disability, 16.5% screened positive. In contrast, 63 (95.5%) of those with severe motor impairment (odds ratio 42; 95% confidence interval [CI] 12.9-135) and 175 (55.9%) of those with cognitive impairment (odds ratio 5.3; CI 3.5-8) screened positive. All children with a significant vision or hearing impairment screened positive. INTERPRETATION: The prevalence of positive M-CHAT screens in extremely preterm children is high, especially in children with neurodevelopmental impairment. Positive screens should be interpreted in the light of other neurodevelopmental sequelae in clinical practice to avoid false-positive referrals.

Relationship between test scores using the second and third editions of the Bayley Scales in extremely preterm children.

OBJECTIVE: To define the relationship between current Bayley Scales of Infant and Toddler Development, Third edition (Bayley-III) scores and the Bayley Scales of Infant Development, second edition Mental Development Index (MDI) to aid the comparison of population outcomes. STUDY DESIGN: MDI and Bayley-III cognitive/language scales were administered concurrently in 185 extremely preterm children (≤26 weeks) at 29-41 months of age. Cognitive and language scores were combined (combined Bayley-III score [CB-III scores]) for comparison with MDI scores. RESULTS: Bayley-III cognitive and language scores were 10 and 3 points higher than MDI scores, respectively; CB-III scores were 7 points higher. The relationship between CB-III and MDI scores was not a simple offset: CB-III values were increasingly higher than MDI at lower scores. Bayley-III scores underidentified MDI scores <70 (sensitivity 58%; specificity 100%). An algorithm for converting Bayley-III scores into MDI scores improved predictive value (sensitivity 95%; specificity 97%). Bayley-III scores <80 were similarly predictive (sensitivity 89%; specificity 99%). CONCLUSIONS: We recommend caution in the interpretation of Bayley-III scores in population studies as the correlation with the previous edition appears worse at lower test score values and the predictive value for IQ is as yet unclear.