Unbound bilirubin and bilirubin-albumin binding levels of Japanese neonates

Objective: To determine postnatal changes in total serum bilirubin (TB), unbound bilirubin (UB), and bilirubin-binding affinity of albumin (Ka) among Japanese newborns. Study design: In a retrospective study, we evaluated for serum TB, UB, and albumin (Alb) levels, and their calculated UB/TB ratios, and Ka in 786 neonates born >= 36 weeks' gestation and analyzed to subcategories of three postnatal epochs: first, second, and >= third weeks. Result: TB levels were significantly higher (p < 0.01) at age >= three weeks, while UB levels were significantly higher (p < 0.01) in the first week. UB/TB ratios were significantly lower while calculated Ka values were significantly higher as age-in-weeks increased (p < 0.01). Conclusion: Hyperbilirubinemia in the first and second weeks of age in neonates born >= 36 weeks' gestation is associated with higher UB levels or UB/TB ratios with lower Ka and may potentially contribute to the risk of developing bilirubin neurotoxicity with aggravated variations in bilirubin, albumin and Ka.