SNAP-II and SNAPPE-II and the risk of structural and functional brain disorders in extremely low gestational age newborns: the ELGAN study

Abstract

Background: Illness severity measures predict death and illnesses in the newborn. It is unknown how well they predict brain lesions evident on ultrasound scans or neurodevelopmental dysfunctions in preterm infants.

Methods: A total of 1,399 inborn infants born before the 28th week of gestation were given Scores for Neonatal Acute Physiology (SNAP-II and SNAPPE-II) based on data collected within the first 12 h of admission to the intensive care unit and had a protocol brain ultrasound scan read independently by 2 sonologists. Of the surviving 1,149 infants, 1,014 (88%) had a neurologic examination at approximately 24 months post-term equivalent, and 975 (85%) had a Bayley Scales of Infant Development assessment. SNAP-II and SNAPPE-II were dichotomized at arbitrary cut-offs (30 for SNAP-II and 45 for SNAPPE-II), using the highest quartile and decile of the week of gestation as a cut-off, and at a Z score of >1 standard deviation from an external mean.

Results: After adjustment for gestational age, high SNAP-II and SNAPPE-II scores predicted intraventricular hemorrhage, moderate/severe ventriculomegaly and echodense lesions in cerebral white matter. Only 2 SNAP-II extremes, the highest decile for gestational age and a Z score >1, also predicted echolucent lesions in the white matter. Neither SNAP-II nor SNAPPE-II predicted any statistically significant diagnosis of cerebral palsy. MDI and PDI scores <55 were consistently predicted by both high SNAP-II and SNAPPE-II, whereas scores in the 55-69 range were inconsistently predicted. High SNAP-II and SNAPPE-II inconsistently predicted a positive screen for autism spectrum disorder and small head circumference at 24 months.

Conclusion: The physiologic instability in the first 12 post-natal hours identified by illness severity scores conveys information about the risks of brain damage and neurodevelopmental dysfunctions. This risk information might reflect postnatal characteristics in the causal chain. On the other hand, high SNAP scores might be indicators of immaturity and vulnerability.