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Correction of developmental and intelligence test scores for premature birth
A L Rickards1, W H Kitchen, L W Doyle
1Department of Obstetrics and Gynaecology, University of Melbourne, Parkville, Victoria, Australia.
Insights
Correcting developmental test scores for prematurity is crucial for preterm infants. Adjusting scores until age 8.5 years improves accuracy in predicting later intelligence, especially for extremely premature children.
Area of Science:
- Developmental Psychology
- Pediatric Neurodevelopment
Background:
- Age correction for prematurity in developmental testing is debated.
- Disagreement exists on whether and when to cease age adjustments.
Purpose of the Study:
- To evaluate the clinical implications of using corrected vs. uncorrected developmental test scores.
- To determine the optimal age range for applying prematurity corrections.
Main Methods:
- Theoretical modeling of score differences.
- Analysis of Bayley Mental Development Index (MDI) and Wechsler Preschool and Primary Scales of Intelligence (WPPSI) scores in 174 very low birthweight children.
- Comparison of corrected and uncorrected scores.
Main Results:
- Failure to correct reduced MDI by 12.1 points and WPPSI by 4.1 points.
- Uncorrected scores showed increased disparity with decreasing gestational age.
- Corrected scores improved MDI's prediction of WPPSI category from 54.6% to 86.1%.
Conclusions:
- Correcting test scores for prematurity is recommended between ages 2-8.5 years.
- This age range ensures more accurate developmental assessments for preterm children.
- The impact of non-correction is most significant in extremely premature infants.
Abstract:
When using tests of infant development and intelligence in children born prematurely, the subject's age is commonly corrected for the degree of prematurity. However, there is disagreement: first, on whether this correction should ever be applied, and second, at what age to discontinue the adjustment. In a theoretical model, the difference between corrected and uncorrected scores in early infancy was massive and the difference remained clinically important until the age of 8.5 years in children who were born extremely prematurely. The clinical implications of using corrected or uncorrected scores were then evaluated in 174 very low birthweight children without severe sensorineural disabilities and with paired Bayley Mental Development Index (MDI) and Wechsler Preschool and Primary Scales of Intelligence (WPPSI) full scale scores. Failure to correct for prematurity reduced the mean MDI by 12.1 points but reduced the mean WPPSI by only 4.1 points. The disparity between individual MDI and WPPSI scores increased significantly with decreasing gestational age if uncorrected scores were used (P = 0.015) but not if scores were corrected. Using corrected scores, the MDI correctly predicted the WPPSI category in 86.1% of children (P less than 0.001) but in only 54.6% using uncorrected scores (the difference was not significant). It is suggested that a practical solution to the dilemma is to correct test scores for prematurity in the age range 2-8.5 years recognizing that only in extremely immature infants will uncorrected scores be substantially lower than corrected ones at a later age.