Surveillance of extreme hyperbilirubinaemia in Denmark. A method to identify the newborn infants

Aim: To describe the incidence of infants born at term or near-term with extreme hyperbilirubinaemia. Methods: The study period was between 1 January 2002 and 31 December 2005, and included all infants born alive at term or near-term in Denmark. Medical reports on all newborn infants with a total serum bilirubin concentration (TSB) >= 450 mu mol/L were obtained by linking laboratory data to the unique Danish personal identification number. Results: In total, 113 infants were included, that is, an incidence of 45/100 000 live births. Thirty-seven infants presented in hospital, 2 after home birth and the others after having been discharged. The maximum TSB was 485 (450-734) mu mol/L (median [range]) and appeared latest amongst those infants admitted from home, but was not different from the maximum TSB of the nondischarged infants. Forty-three infants had symptoms of early-phase acute bilirubin encephalopathy; one infant had advanced-phase symptoms. Four infants received an exchange transfusion. ABO blood group incompatibility was present in 52 infants. Thirty-seven infants were of non-Caucasian descent. Conclusion: A method to obtain the national epidemiological data is presented. The observed incidence of extreme hyperbilirubinaemia is higher than previously reported in Denmark. This is mainly due to a very sensitive method of identifying the study group.