Unbound Bilirubin and Prematurity

A recent prospective study (SB Amin, H Wang. J Pediatr 2018; 192: 47-52) indicates that premature infants have lower bilirubin binding affinity which could place them at risk for neurological complications.

Background: Very high levels of unconjugated bilirubin can lead to bilirubin-induced neurotoxicity/kenricterus.  There is increased susceptibility in newborns, particularly premature infants.  Unbound bilirubin (not bound to protein) can cross blood-brain barrier.  However, unbound bilirubin, rather than total serum bilirubin, is a better predictor of abnormal neurological outcomes.

Key findings:

  • Among 166 infants, peak unbound bilirubin significant correlated with bilirubin-albumin binding affinity (Ka) (r=-0.44, P=.001)
  • Gestational age was a significant modifier for the association between Ka and peak unbound bilirubin.
  • Peak unbound bilirubin was primarily associated with a decrease in binding affinity in infants ≤30 weeks gestational age

Implications of study: “Phototherapy as a sole intervention may be insufficient in preventing or reducing bilirubin-induced neurotoxicity”

My take: If there is low bilirubin binding affinity, among premature infants ≤30 weeks gestational age, some neurologic toxicity could occur even with bilirubin levels that have been considered safe previously.

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