title: Anti-A and anti-B titers in pooled group O platelets are comparable to apheresis platelets.
abstract: BACKGROUND
  Although uncommon, acute hemolytic transfusion reactions (AHTRs) have been reported after transfusion of group O single-donor apheresis platelets (SDPs) to group A, B, and AB recipients. Current methods for identifying "high-titer" SDPs include tube and gel methods. The risk of a high-titer unit is considered low with group O, poststorage, pooled platelet concentrates (PPLTs); however, data regarding anti-A and anti-B titers in PPLTs are lacking.
  
  
  METHODS
  Anti-A and anti-B titers were determined in 185 PPLTs by direct agglutination using manual gel and tube methods. PPLTs tested included 124 group O PPLTs, 25 group A PPLTs, 26 group B PPLTs, and 10 PPLTs containing a mix of either groups O plus A or groups O plus B (mixed PPLTs). The reciprocal of the highest dilution giving macroscopic agglutination was considered the agglutinin titer.
  
  
  RESULTS
  Mean anti-A and anti-B titers in group O PPLTs were, respectively, 16 and 8 by tube and 64 and 32 by gel (p < 0.0001). Gel titers were one to two dilutions higher than tube and sensitive to reagent red cell lots. With the use of at least 64 as a critical titer, 60 percent of group O PPLTs tested by gel would be considered high-titer. In mixed PPLTs, the addition of one non-group O PLT significantly decreased or neutralized the corresponding anti-A or anti-B (p < 0.0001).
  
  
  CONCLUSIONS
  Anti-A and anti-B titers in group O PPLTs are comparable to those reported in group O SDPs and significantly lower than titers reported in AHTR. A critical direct agglutinin titer of 64 for identifying high-titer units by gel is too low and should be increased to 128 or higher.
authors.affiliation: Department of Pathology, University of Michigan Hospitals, Ann Arbor, Michigan 48109-0054, USA. lcooling@med.umich.edu
authors.forename: Laura L
authors.initials: LL
authors.lastname: Cooling
authors.forename: Theresa A
authors.initials: TA
authors.lastname: Downs
authors.forename: Suzanne H
authors.initials: SH
authors.lastname: Butch
authors.forename: Robertson D
authors.initials: RD
authors.lastname: Davenport
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000208:Acute Disease; D000372:Agglutination Tests / Q000379:methods; D016824:Antigens, Human Platelet / Q000276:immunology*; D001781:Blood Component Removal; D001787:Blood Group Incompatibility / Q000453:epidemiology / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology; D006801:Humans; D007519:Isoantigens / Q000097:blood / Q000276:immunology*; D017713:Platelet Transfusion / Q000009:adverse effects* / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D000017:ABO Blood-Group System; D016824:Antigens, Human Platelet; D007519:Isoantigens