Among patients with intracerebral hemorrhage (ICH), transfusing ABO-incompatible platelets may lead to worse clinical outcomes and slower platelet recovery, according to research published in Blood.

ICH may result in continuous bleeding or hematoma expansion, both of which are linked with worse clinical outcomes. Previous research suggests, furthermore, that platelet transfusions, which are used particularly among patients with platelet dysfunction, may worsen outcomes, rather than benefitting patients. However, the underlying mechanisms for this finding are not clear.

It was also previously unclear whether ABO incompatibility in platelet transfusions plays a causal role in these negative outcomes. For this single-cohort study, researchers evaluated whether ABO incompatibility, as compared with ABO compatibility, is predictive of clinical outcomes among patients undergoing transfusion for ICH.

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Overall, 125 patients were included, among whom 47 received an ABO-incompatible transfusion and 78 received an ABO-compatible transfusion. In the ABO-incompatible and -compatible groups, the mean age was 64 vs 65 years, respectively; 55.3% vs 59% of patients were male, 80.9% vs 73.1% of patients had past hypertension, and 74.5% vs 57.7% of patients had a deep ICH.

Patients who underwent ABO-incompatible transfusion (absolute count increment, 2 × 103 cells/uL) had lower platelet recovery than did those who underwent ABO-compatible transfusion (absolute count increment, 15 x 103 cells/uL; P =.01)

Patients in the ABO-incompatible transfusion group also had a higher risk of mortality (adjusted odds ratio, 2.49; P =.05). Morbidity also appeared to be worse in this group, although the authors stated that these findings may have been imprecise.

“However, at the very least, our findings appear to be consistent with analogous studies in non-ICH patient populations showing that ABO-incompatible platelet transfusions are associated with poor platelet recovery and increased morbidity,” the authors wrote. “Additional prospective studies will be required to assess whether ABO-identical platelet transfusions are indicated in this vulnerable patient population.”


Magid-Bernstein J, Beaman CB, Carvalho-Poyraz F, et al. Impacts of ABO-incompatible platelet transfusions on platelet recovery and outcomes after intracerebral hemorrhage. Blood. 2021;137(19):2699-703. doi:10.1182/blood.2020008381