Platelets express numerous surface antigens including A, B, and H; and the plasma in which they are suspended contain the corresponding donor isohemagglutinins (antibodies to A or B antigen). Transfusion of incompatible platelets may result in hemolysis. However, because the risk is low, the practice of providing ABO-nonidentical (ABON) or ABO-identical (ABOI) platelets to patients varies among institutions, with some providing platelets of any ABO type in a first-in first-out manner and others providing ABOI platelets to certain patient subgroups including hematology and oncology patients and children. Smaller hospitals with lower stock levels may not have this option.
A systematic review and meta-analysis by Cheng and colleagues compared the clinical safety and efficacy of ABON platelets to that of ABOI platelets (1). The study included 104,359 platelet transfusions from 11 retrospective and 7 prospective cohort studies between 1987 and 2023. Primary outcomes were (1) transfusion effectiveness as measured by whether the corrected count increment (CCI) or percent platelet recovery (PPR) exceeded specified values and (2) the 24-hour CCI. Data was inadequate to study platelet transfusion refractoriness (PTR). Secondary outcomes were adverse reactions and mortality.
This study divided platelet transfusions into two categories–ABOI, in which recipient and donor have the same ABO type; and ABON, which includes minor, major, and bidirectional incompatibilities (Table 1).
Table 1. Platelet ABO compatibility
| Recipient ABO antigens (isohemagglutinins) | ||||
| Donor ABO antigens (isohemagglutinins) | AB (no antibodies) | A (anti-B) | B (anti-A) | O (anti-A, anti-B) |
| AB (no antibodies) | Identical | Major inc. | Major inc. | Major inc. |
| A (anti-B) | Minor inc. | Identical | Bidirectional inc. | Major inc. |
| B (anti-A) | Minor inc. | Bidirectional inc. | Identical | Major inc. |
| O (anti-A, anti-B) | Minor inc. | Minor inc. | Minor inc. | Identical |
Minor inc.: minor incompatibility. Donor antibody is incompatible with recipient antigens.
Major inc.: major incompatibility. Donor antigen is incompatible with recipient isohemagglutinins.
Identical: ABO type and isohemagglutinins of donor and recipient are identical.
Bidirectional inc.: bidirectional incompatibility. Major and minor incompatibility occurs.
Transfusion effectiveness was investigated by analysis of extracted data from six studies (1653 transfusions). ABOI transfusions were effective at the same rate as minor-incompatible transfusions. ABOI transfusions and minor-incompatible transfusions were effective more often than major-incompatible transfusions.
Platelet increment data obtained from 3 of the studies (7326 transfusions) showed higher, but not significantly higher, values in ABOI transfusions compared to ABON transfusions (P=0.06). This appears to contradict the finding that the transfusion effectiveness of ABOI platelets is superior to that of ABON platelets. The discrepancy might be attributed to the fact that the studies supporting the findings were different.
Adverse event data from five studies (14,777 transfusions) showed increased frequency of allergy and fever when ABON platelets were given compared to ABOI platelets. In one large study (2), three cases of acute intravascular hemolysis in 2522 ABON transfusions were reported. Two cases were minor-incompatible and one was bidirectional-incompatible. There was no difference in mortality between ABOI and ABON transfusions, whether patients received two or fewer transfusions or greater than two transfusions, although the times between the first and last transfusions were not given.
In closing, this study confirmed that ABO-identical platelet transfusions may improve transfusion efficacy and reduce some types of adverse events. However, the study noted that a randomized controlled trial is needed to establish that ABOI transfusions reduce bleeding more than ABO-nonidentical transfusions do and that ABOI transfusions are safer. Furthermore, the study did not consider platelets collected in platelet additive solutions. These products have the theoretical advantage of lower isohemagglutinin amounts, but the extent to which they actually mitigate the disadvantages of ABON transfusions has not been determined.
- Cheng Z, Kong Y, Lin Y, et al. Transfusion outcomes and clinical safety of ABO-nonidentical platelets transfusion: a systematic review and meta-analysis. Transfus Apher Sci [Internet]. 2024 May 19 [cited 2024 Jun 25]. https://doi.org/10.1016/j.transci.2024.103943.
- Malvik N, Leon J, Schlueter AJ, Wu C, Knudson CM. ABO-incompatible platelets are associated with increased transfusion reaction rates. Transfusion. 2020 Feb;60(2):285-293. https://doi.org/10.1111/trf.15655.
