False-negative results of pre-discharge neonatal bilirubin screening to predict severe hyperbilirubinemia: a need for caution

Routine bilirubin screening prior to newborn hospital discharge, using an hour-specific bilirubin nomogram, has been advocated to assess risk for subsequent severe hyperbilirubinemia. However, the false-negative rate has never been adequately studied. Our objective was to determine false-negative results of pre-discharge bilirubin screening. After routine pre-discharge, bilirubin screening was in place for over 4 years, we performed a retrospective chart review to identify infants readmitted for total bilirubin levels > 17 mg/dl (>290.7 μmol/l). We documented each infant's pre-discharge bilirubin level, risk-zone assignment by nomogram, the presence or absence of risk factors for severe hyperbilirubinemia, co-morbidities upon readmission, treatment received, and ultimate disposition. Readmitted infants whose pre-discharge bilirubin was in the low-risk (<40th percentile) and low-intermediate (40–75th percentile) risk zones of the nomogram, were considered false-negatives. Of the 6,220 infants discharged from the newborn nursery during the 51-month study period, 28 (0.45%) were readmitted for treatment of serum bilirubin levels > 17 mg/dl (>290.7 μmol/l). All received phototherapy and none required exchange transfusion. Pre-discharge bilirubin values were <40th percentile (low-risk zone) in one infant (3.6%), and between 40–75th percentiles (low-intermediate risk zone) in twelve infants (43%). Risk factors for the development of severe hyperbilirubinemia were present in 27 (96%) readmitted infants. In conclusion, nearly half of readmitted infants had pre-discharge bilirubin values in zones considered at lower risk. The use of pre-discharge bilirubin screening alone to assign future risk for severe hyperbilirubinemia may provide false reassurance. Rigorous research is required to determine the test characteristics of pre-discharge bilirubin screening before widespread acceptance and implementation. Universal early post-discharge follow-up should remain the cornerstone of preventing severe hyperbilirubinemia.