title: Direct antiglobulin titer strength and hyperbilirubinemia.
abstract: OBJECTIVE
  We recently demonstrated that direct antiglobulin titer (DAT) positive, blood group A or B newborns born to group O mothers had a high incidence of hyperbilirubinemia, attributable to increased hemolysis. We reanalyzed our data asking whether increasing DAT strength plays a modulating role in the pathophysiology of the hemolysis and hyperbilirubinemia.
  
  
  METHODS
  Data from previously published DAT-positive, ABO-heterospecific neonates were analyzed for hyperbilirubinemia and hemolysis according to strength of DAT. DAT was measured by using a gel agglutination technique and reported as values ranging from DAT ± to DAT ++++. Hemolysis was evaluated by blood carboxyhemoglobin corrected for inspired, ambient CO (COHbc), and expressed as percent total hemoglobin (tHb). Hyperbilirubinemia was defined as any plasma total bilirubin value >95th percentile on the hour-specific nomogram.
  
  
  RESULTS
  Hyperbilirubinemia was more prevalent in those with DAT ++ readings (16 of 20, 80%) than those both DAT ± (37 of 87 [42.5%], relative risk: 1.88, 95% confidence interval: 1.35-2.61) and DAT + (32 of 56 [57.1%], relative risk: 1.40, 95% confidence interval: 1.02-1.92). COHbc values were higher for those with DAT ++ (1.45 ± 0.49% tHb [mean ± SD]) than those DAT ± (1.20 ± 0.37% tHb, P = .01) or DAT + (1.22 ± 0.37% tHb, P = .02).
  
  
  CONCLUSIONS
  DAT ++ readings were associated with a higher incidence of hyperbilirubinemia and higher COHbc values than DAT ± or DAT + counterparts. Increasing DAT strength may be a modulator of hemolysis and hyperbilirubinemia in ABO-heterospecific neonates. DAT strength, and not merely DAT presence or absence, should be taken into consideration in the management of ABO-heterospecific newborns.
authors.affiliation: Department of Neonatology, Shaare Zedek Medical Center, Jerusalem, Israel; Faculty of Medicine of The Hebrew University, Jerusalem, Israel; and mkaplan@mail.huji.ac.il.
authors.forename: Michael
authors.initials: M
authors.lastname: Kaplan
authors.affiliation: Department of Neonatology, Shaare Zedek Medical Center, Jerusalem, Israel; Faculty of Medicine of The Hebrew University, Jerusalem, Israel; and.
authors.forename: Cathy
authors.initials: C
authors.lastname: Hammerman
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, California.
authors.forename: Hendrik J
authors.initials: HJ
authors.lastname: Vreman
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, California.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wong
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, California.
authors.forename: David K
authors.initials: DK
authors.lastname: Stevenson
mesh_terms: D001663:Bilirubin / Q000097:blood*; D001789:Blood Group Antigens / Q000097:blood; D015331:Cohort Studies; D003298:Coombs Test / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D006932:Hyperbilirubinemia / Q000097:blood* / Q000175:diagnosis*; D007231:Infant, Newborn; D008297:Male
chemical_list: D001789:Blood Group Antigens; D001663:Bilirubin
keywords: ABO heterospecificity; carboxyhemoglobin; direct antiglobulin titer; hemolysis; hyperbilirubinemia