Background: In the pediatric population, hemolysis after out-of-group platelet (PLT) transfusion is a potentially fatal event that is thought to be underrecognized. Group A patients transfused with group O single-donor PLTs (SDPs) with "high-titer" anti-A are at greatest risk for hemolysis.
Study design and methods: A clinical and serologic evaluation of a pediatric patient with hemolysis of initially unknown etiology was conducted. Retrospective testing for anti-A titer of an admission sample and a transfused group O SDP was performed.
Results: The group A patient (previously group O) was found to have a history of engrafted major ABO-mismatched hematopoietic peripheral blood progenitor cell transplant (HPBPCT). Immune-mediated intravascular hemolysis with a delayed presentation was determined. Testing identified passive anti-A in the patient's plasma and high-titer anti-A (IgG 4096, IgM 256) in the group O SDP unit.
Conclusion: Hemolysis after out-of-group SDP transfusion may be delayed in presentation and, thus, clinically unrecognized. When evaluating these cases, the limitations of routine type and screen for detection of passive anti-A must be considered. Group A individuals with a history of engrafted major ABO-mismatched HPBPCT potentially have increased susceptibility to hemolysis from group O SDP transfusion due to their lack of tissue and soluble A antigen.