Evaluation of platelet transfusions from Histocompatibility locus: a matched and nonmatched unrelated donors to thrombocytopenic patients

Prolonged platelet transfusion therapy often tends towards a refractory state in the thrombocytopenic patient. This may be caused by alloimmunization (isoimmunizaytion) to platelet antigens, especially transplantation antigens of the Histocompatibility locus-A (HL-A) system. Histocompatibility between patient and donor is essential for the hemostatic effectiveness of transfused platelets. In this study, platelet transfusions were studied in 19 patients exhibiting different thrombocytopenic states. The number and frequency of platelet transfusions were determined by the recipient's physician(s). All patients that received ABO specific non HL-A matched platelets became refractory after 30 units. Patients that received ABO specific non HL-A matched platelets, bleeding severely and had received blood transfusion six months prior to this study, demonstrated the lowest 20 hour increments of all group investigated. They demonstrated median and mean increments of 1,230 X M2/unit and 890 X M2.unit respectively. Patients that received ABO specific non HL-A matched platelets, not actively bleeding and had not received blood transfusions six months or longer prior to this study, responded with a median and mean 20 hour increments of 19,460 X M2/unit and 21,460 X M2/unit respectively. These values are similar to those of non-sensitized patients receiving non HL-A matched platelets over a short period of time. One patient received ABO, HL-A matched compatible platelets. He did not show the expected response. This was probably due to sensitization to non HL-A antigens and specific platelet antigens from prior numerous blood transfusion. The patient died soon after admission into the hospital. Two patients received both HL-A matched platelets. The median and mean 20 hour increments were 940 X M2/unit and 3,380 X M2/unit with HL-A matched platelets as compared to 200 X M2/unit 400 x M2/unit respectively with non HL-A matched platelets. The feasibility of establishing a volunteer HL-A platelet donor program was also investigated. At this time it appears a 100 percent volunteer donor program is not possible until such time of greater public, physician, and blood transfusion services education, and awareness of the necessity of HL-A matched platelets in prolonged platelet therapy. Utilizing occasional paid donors it was possible to establish a HL-A match platelet transfusion program.