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Impact of a matched term control group on interpretation of developmental performance in preterm infants
S J Gross1, T A Slagle, D B D'Eugenio
1Department of Pediatrics, State University of New York, Health Science Center, Syracuse 13210.
Insights
Using a control group significantly impacts preterm infant cognitive outcome classification. Preterm children appeared more often normal when using test norms versus control group performance, affecting delay identification.
Area of Science:
- Developmental Pediatrics
- Neuroscience
- Cognitive Psychology
Background:
- Preterm birth is associated with neurodevelopmental challenges.
- Accurate cognitive assessment is crucial for early intervention in preterm infants.
- Standardized tests rely on normative data, which may not always reflect specific populations.
Purpose of the Study:
- To compare cognitive outcome classifications of preterm children using different normative references.
- To evaluate the impact of using a matched term control group versus published test norms for defining cognitive status.
- To assess the prevalence of normal, mild-moderate, and severe cognitive delays in preterm infants.
Main Methods:
- Serial developmental evaluations of 124 preterm infants (24-31 weeks gestation) and 124 matched term controls.
- Cognitive outcomes assessed using the Bayley Mental Developmental Index (BMDI) at 6, 15, and 24 months and McCarthy General Cognitive Index (MGCI) at 4 years.
- Classification of cognitive status (normal, mild-moderate, severe delay) based on two normative standards: published test scores and the performance of the term control group.
Main Results:
- The term control group exhibited significantly higher BMDI scores than published test norms at 6, 15, and 24 months.
- Consequently, a higher percentage of preterm children were classified as normal when using published norms compared to the control group (e.g., 84% vs. 52% at 6 months).
- Severe cognitive delays were identified more frequently (2-3 times greater) when using the control group's performance as the benchmark.
Conclusions:
- The choice of normative data significantly influences the classification of cognitive outcomes in preterm infants.
- Using a matched term control group provides a more conservative and potentially more accurate assessment of cognitive development compared to published norms.
- These findings highlight the importance of carefully selecting reference groups for developmental assessments in high-risk populations.
Abstract:
One hundred twenty-four children who were born at 24 to 31 weeks' gestation and 124 term children matched in social background underwent serial developmental evaluations. The Bayley Mental Developmental Index at 6, 15, and 24 months and the McCarthy General Cognitive Index at 4 years were used to classify cognitive outcome for preterm children as normal (indices higher than 1 SD below the mean), mild-moderately delayed (indices between 1 and 2 SD below the mean), or severely delayed (indices > or = 2 SD below the mean). Classifications based on norms derived from the performance of the term control group were compared with those based on published standardized test scores. The control group had substantially higher mean (+/- SD) Bayley Mental Developmental Indices at 6 (111 +/- 11), 15 (114 +/- 13), and 24 months (115 +/- 21) than the published test mean (100 +/- 16). Consequently, significantly more preterm children were classified as normal when the Bayley test mean was used than when the performance of the control group was used to define the normal range (84% vs 52% at 6 months, 82% vs 49% at 15 months, and 70% vs 47% at 24 months). Severe cognitive delays were infrequent when defined by test mean (6% to 11%) but two to three times greater when the control group scores were used. In contrast, the control group had a mean McCarthy General Cognitive Index at 4 years (102 +/- 14) that was similar to the published test mean (100 +/- 16).(ABSTRACT TRUNCATED AT 250 WORDS)