A poor increment in the platelet count 1 hour after transfusion is most commonly caused by which factor?

A poor increment in the platelet count 1 hour after transfusion is often attributed to alloimmunization to HLA antigens. This condition occurs when a patient develops antibodies against human leukocyte antigens (HLA) present on the transfused platelets. When a person receives platelets from a donor and has prior exposure to HLA through previous transfusions or pregnancies, their immune system can recognize the donor platelets as foreign and mount an immune response against them. This leads to destruction of the transfused platelets shortly after infusion, resulting in a minimal or absent increment in the platelet count.

While splenomegaly can also impact platelet survival due to increased sequestration in an enlarged spleen, alloimmunization specifically relates to the immune-mediated destruction of transfused platelets. Conditions like disseminated intravascular coagulation and defective platelets can affect overall hemostasis and platelet function but are less commonly associated with the prompt decline noted after a transfusion. Therefore, alloimmunization to HLA antigens is the most common factor leading to the poor increment seen in platelet counts shortly after transfusion.