[2008] [5844.21] Direct Coombs' Positive O-B Bloodgroup Heterospecificity: A Risk Factor for Neonatal Hyperbilirubinemia and Hemolysis

Michael Kaplan, Cathy Hammerman, Hendrik J. Vreman, Ronald J. Wong, David K. Stevenson. Shaare Zedek Medical Center, Jerusalem, Israel; Hebrew University, Jerusalem, Israel; Stanford University School of Medicine, Stanford, CA.

BACKGROUND: Direct Coombs' positive ABO bloodgroup heterospecificity (mother group O, newborn A or B) is a common cause of immune hyperbilirubinemia.
OBJECTIVE: We compared the incidence of hyperbilirubinemia and degree of hemolysis between direct Coombs' positive, blood group A and B newborns of group O mothers.
DESIGN/METHODS: Consecutive, direct Coombs' positive group A or B newborns, >36 weeks gestation, born at Shaare Zedek Medical Center to group O mothers were assessed by the nursing staff several times daily for jaundice. A plasma total bilirubin (PTB) determination was obtained as deemed necessary by this clinical evaluation. At the time of discharge, all neonates had a mandatory PTB as well as blood drawn for carboxyhemoglobin (COHb) determination (a sensitive index of bilirubin formation). Ambient air was sampled concurrently for determination of its CO content. Hyperbilirubinemia was defined as any PTB concentration >95th percentile on the hour of life specific bilirubin nomogram (Bhutani et al, 1999), and early hyperbilirubinemia as any PTB >95th percentile prior to 24 hours of life. Phototherapy was administered in accordance with the 2004 AAP guidelines for neonates with risk factors. COHb was measured by a gas chromatographic method at Stanford University, expressed as a % of total Hb (tHb) and corrected for ambient CO, to derive COHbc.
RESULTS: Data are summarized in the Table.

ItemOverallO-AO-BSignificance O-B vs. O-A
Number of infants162110 (67%)52 (33%)
Hyperbilirubinemia (n, incidence)84 (52%)51 (46%)33 (64%)*OR 2.0 (1.02-4.0)
Hyperbilirubinemia <24 hr53 (33% of total)28 (26%)25 (48%)*OR 2.71 (1.36-5.42)
Phototherapy (n, incidence)80 (49%)47 (43%)33 (64%)*OR 2.33 (1.18-4.59)
COHbc (%tHb)1.24±0.401.20±0.381.34±0.43*p=0.038
OR: Odds Ratio (95% confidence interval); COHbc: corrected carboxyhemoglobin. For reference, COHbc values in Coombs' negative newborns in the same nursery were 0.77± 0.19%

No infant went on to require IVIG therapy or exchange transfusion.
CONCLUSIONS: Overall, Coombs' positive ABO heterospecificity was associated with a high incidence of PTB >95th percentile and a high rate of hemolysis. O-B heterospecificity conferred a higher incidence of hyperbilirubinemia and greater degree of hemolysis than O-A counterparts.


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