Newborn Hyperbilirubinemia Assessment Calculator — Bhutani Nomogram

Formula

How this is calculated

Neonatal hyperbilirubinemia (jaundice) is nearly universal in the first week of life; the concern is identifying infants at risk of severe hyperbilirubinemia, which can lead to kernicterus (bilirubin-induced brain damage). The Bhutani nomogram, published in Pediatrics in 1999, provides hour-specific bilirubin percentile reference curves (P40, P75, P95) derived from a large cohort of healthy term and near-term neonates. Plotting the TSB against postnatal age in hours places the infant in one of four risk zones: low (below P40), low-intermediate (P40–P75), high-intermediate (P75–P95), or high (above P95).

This calculator uses piecewise linear interpolation over the published percentile values to estimate the zone boundaries at any postnatal age between 12 and 144 hours. It also applies simplified AAP 2004 phototherapy thresholds — adjusted downward by approximately 3 mg/dL when neurotoxicity risk factors (isoimmune haemolysis, G6PD deficiency, asphyxia, sepsis, albumin < 3 g/dL) are present.

Important limitations: the nomogram was validated for ≥ 36 weeks gestational age in healthy neonates without active haemolysis; preterm infants and those with haemolytic disease have different risk profiles. The 2022 AAP guidelines introduced updated gestational age–specific phototherapy thresholds that differ from the 2004 values used here. This tool provides a reference estimate only — clinical decisions must be made by trained neonatal staff using current AAP resources or the BiliTool calculator.