Carboxyhemoglobin measurements in the diagnosis of ABO hemolytic disease.

To assess hemolysis in hyperbilirubinemic infants with ABO isoimmunization, we measured the carboxyhemoglobin (HbCO) concentrations in full-term infants with ABO isoimmunization during the first week of life. Two groups of infants, ABO compatible (n = 34) and ABO incompatible (n = 30), were further divided into two groups with and without hyperbilirubinemia. All the infants from ABO incompatible pregnancies showed a positive indirect Coombs' test. The groups with hyperbilirubinemia included infants with maximum serum total bilirubin levels about 15 mg/dL and infants treated by phototherapy or exchange transfusion. In the ABO incompatible infants, the HbCO levels in those with hyperbilirubinemia were significantly higher than in infants without hyperbilirubinemia during the first week after birth (p less than 0.01 at 24, 72, 120 hours after birth, respectively). The levels of HbCO in the ABO incompatible infants with hyperbilirubinemia were significantly higher compared with the levels in the ABO compatible infants with hyperbilirubinemia (p less than 0.05 at 24 hours, p less than 0.01 at 72 and 120 hours after birth, respectively). HbCO measurement may facilitate the early diagnosis of hemolytic disease and the prediction of jaundice caused by ABO isoimmunization.