Peer-reviewed article
Unbound bilirubin-based management of neonatal hyperbilirubinemia: The Japanese experience and global adaptation.
Iwatani S, Morioka I, Nakamura H ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This review describes Japan's approach to managing neonatal hyperbilirubinemia (high bilirubin levels in newborns) using unbound bilirubin measurement rather than total bilirubin alone. Excessive bilirubin can cause brain damage in newborns, particularly preterm infants. Japanese clinicians have developed criteria that consider the active form of bilirubin, gestational age, and other factors to guide treatment decisions. The approach may reduce unnecessary phototherapy while keeping infants safe, though larger studies are needed to confirm benefits.
Key points
- Unbound bilirubin (UB) is the biologically active fraction of bilirubin that causes neurologic dysfunction, not the total bilirubin level alone
- Japan's Nakamura criteria (1991) and Morioka criteria (2017) incorporate UB measurement, gestational age, and albumin binding to guide treatment decisions
- Clinical experience suggests this approach may reduce phototherapy exposure without increasing risk of complications, though multicenter evidence is limited
- Bilirubin-albumin binding characteristics vary between infants and are important for predicting harm risk
- Emerging methods like transcutaneous bilirubin measurement and fluorescence-based tests may improve accessibility of UB monitoring in diverse settings
Limitations
This is a review of clinical experience rather than a formal comparative trial. The document acknowledges that multicenter evidence with long-term neurodevelopmental outcomes is limited, so it is unclear whether this approach actually prevents brain damage better than standard care.
Abstract
Neonatal hyperbilirubinemia is common, but bilirubin-induced neurologic dysfunction (BIND) remains an important cause of preventable morbidity, particularly in preterm infants. Japan has developed a distinctive approach centered on unbound bilirubin (UB), the biologically active fraction. Nakamura and colleagues pioneered neonatal UB measurement in the 1970s and incorporated UB measurements into the Kobe University (Nakamura) criteria in 1991. With improved survival of extremely preterm infants, bilirubin encephalopathy was still observed despite modest total serum bilirubin (TSB) levels that persisted beyond the first postnatal week. These observations led Morioka to revise the criteria in 2017, incorporating gestational age (GA), corrected GA, UB levels, and staged treatment throughout the prolonged neonatal course. Clinical experience suggests that this approach may reduce phototherapy exposure without increasing UB levels or exchange transfusion, although multicenter evidence with long-term neurodevelopmental outcomes remains limited. The Japanese experience emphasizes longitudinal monitoring and bilirubin-albumin binding characteristics beyond TSB levels alone. Transcutaneous bilirubin, albumin, and bilirubin-albumin molar ratio may facilitate screening, while emerging fluorescence-based methods may improve UB accessibility. UB measurement should be viewed as a framework for individualized risk assessment, with principles adaptable to diverse populations and clinical settings.