ABO matching for platelet transfusions for prevention or treatment of bleeding: A systematic review with meta-analysis.

Transfusion of ABO identical platelets is recommended in national guidelines, though transfusion of ABO non-identical platelets has been widely adopted to ensure availability and reduce wastage. When ABO non-identical platelets are necessitated, there is a lack of consensus on prioritisation of major or minor compatibility. We conducted a systematic review and meta-analysis (PROSPERO CRD42023450792) of randomised and non-randomised studies to assess whether there is a difference when comparing ABO-identical and non-identical (major, minor, bi-directional mismatch) platelet transfusions. From 4177 potential references, 18 studies met our criteria: 3 randomised controlled trials (RCTs), 8 prospective and 7 retrospective observational studies. Evidence was very low certainty as to whether there was a difference from transfusion of ABO identical or non-identical platelets, where data were available, for clinically significant (WHO grade 2+ and 3+) bleeding, mortality, acute transfusion reactions, platelet refractoriness. Platelet increments were the most frequently reported outcomes. Overall, there was a paucity of evidence for clinical outcome data including bleeding risk for ABO identical compared to non-identical transfusion. We make recommendations for designing and reporting future platelet ABO matching studies based on our observations in this review. Future studies should consider the effect of repeated exposure to ABO identical or non-identical transfusions and known confounders.