Carboxyhemoglobin blood level in indirect hyperbilirubinemia in term and late-preterm infants as a marker of hemolysis

Background Neonatal hyperbilirubinemia remains one of the most common clinical conditions faced and one of the most common diagnoses requiring neonatal intensive care unit (NICU) admission, and this study aims to investigate whether carboxyhemoglobin (COHB) measurement in blood can be used as a marker for hemolysis in neonates with indirect hyperbilirubinemia or not. This comparative cross-sectional study was carried out on 42 term and late-preterm neonates with gestational age ≥ 35 weeks who were recruited from the Neonatal Intensive Care Unit of Ain Shams University Hospital, Cairo, Egypt. Neonates were divided into 2 groups: group 1 involving 22 neonates with hemolytic hyperbilirubinemia, whereas group 2 had 20 neonates that do have a non-hemolytic cause of hyperbilirubinemia. Carboxyhemoglobin levels were measured by blood gas CO-oximetry on admission and after 48 h. Results Significant difference in the COHb levels on admission was correlated with hemoglobin (Hb) levels on admission, Hb at 48 h, reticulocytes, and lactate dehydrogenase (LDH) (all with P -value < 0.001). It also demonstrated that infants with hemolytic hyperbilirubinemia had significantly higher COHb values either on admission or at 48 h with a mean of 2.4 ± 0.8% on admission in the hemolytic hyperbilirubinemia group versus 1.4 ± 0.2% in the non-hemolytic hyperbilirubinemia group and a mean of 2.0 ± 0.5% at 48 h in the hemolytic hyperbilirubinemia group versus 1.2 ± 0.2% in the non-hemolytic hyperbilirubinemia group; COHb levels on admission and at 48 h have excellent diagnostic value with an area under the ROC curve (AUC) of 0.981 and 0.958, respectively. The best cutoff was COHb > 1.5% on admission and > 1.4% at 48 h. Conclusion COHb measurement on admission or at 48 h with blood gas CO-oximeter was shown to be a sensitive and specific method that serves as an indicator of hemolysis in neonates with hemolytic hyperbilirubinemia, with the best cut-off value of COHb on admission ≥ 1.5% and the best cut-off value of COHb at 48 h ≥ 1.4%.