Relation between serum bilirubin levels ≥450 μmol/L and bilirubin encephalopathy; a Danish population-based study

Aim: Describe the relation between levels of total serum bilirubin (TsB) ≥450 μmol/L and acute intermediate, acute advanced and chronic bilirubin encephalopathy.

Material and methods: All infants born at gestational age ≥35 weeks in Denmark between 2000 and 2007 with a TsB ≥450 μmol/L according to the national laboratory information system. Infants diagnosed with bilirubin encephalopathy were found in the Danish National Registry of Patients.

Results: 502,766 infants at gestational age ≥35 weeks were identified. Two hundred twenty-four developed a TsB ≥450 μmol/L, equivalent to an incidence of 45/100,000/year, and it increased during the period. Incidence of infants with peak TsB of 450-499, 500-599 and 600-1000 μmol/L were 29.6, 12.7 and 2.2 per 100,000, respectively. Three infants had acute advanced bilirubin encephalopathy and got severe sequelae, whereas the two infants with acute intermediate encephalopathy developed normally. Their peak TsB was ≥544 μmol/L. Having a peak TsB 600-1000 μmol/L, the risk of acute advanced and chronic bilirubin encephalopathy was 27% (95% CI 6;61), and the incidence of these conditions was 0.6 (95% CI 0.1;1.7) per 100,000.

Conclusion: The incidence of infants with TsB ≥450 μmol/L was 45/100,000/year. Infants with a TsB ≥600 μmol/L had a substantial risk of developing acute advanced and chronic bilirubin encephalopathy, and the incidence of these conditions was 0.6 per 100,000.