Bilirubin kinetics in preterm infants.

BACKGROUND: Preterm infants are vulnerable to bilirubin neurotoxicity. We evaluated whether time-stratified transcutaneous bilirubin (TcB) and kinetic indices improve the prediction of the risk of phototherapy and escalation. METHODS: In a cohort of preterm infants, only pre-phototherapy TcB values were analyzed. TcB values were grouped by postnatal age (≤24 h, 25-48 h, 49-72 h, ≥73 h), and sequential measurements were used to calculate bilirubin increase rates (RBIa, RBIb) and absolute percent change (APC%). RESULTS: Infants requiring phototherapy had higher TcB levels within 72 h, particularly at ≤24 h and 25-48 h. Independent predictors included TcB (OR 2.11), gestational age (OR 0.37), and postnatal age (OR 0.30; AUC 0.827). Treated infants showed faster bilirubin accumulation, and early RBIa correlated with peak TcB (r = 0.334). APC% independently predicted proximity to the escalation threshold. CONCLUSIONS: Time-standardized TcB measurements and dynamic kinetic indices may facilitate earlier identification of preterm infants at increased risk for phototherapy and warrant prospective validation.