Factors affecting posttransfusion platelet increments, platelet refractoriness, and platelet transfusion intervals in thrombocytopenic patients

Abstract

A variety of patient and product-related factors influenced the outcome of 6379 transfusions given to 533 patients in the Trial to Reduce Alloimmunization to Platelets (TRAP). Responses measured were platelet increments, interval between platelet transfusions, and platelet refractoriness. Patient factors that improved platelet responses were splenectomy and increasing patient age. In contrast, at least 2 prior pregnancies, male gender, splenomegaly, bleeding, fever, infection, disseminated intravascular coagulation, increasing height and weight, lymphocytotoxic antibody positivity, an increasing number of platelet transfusions, or receiving heparin or amphotericin were associated with decreased posttransfusion platelet responses. Platelet factors that were associated with improved platelet responses were giving ABO-compatible platelets, platelets stored for 48 hours or less, and giving large doses of platelets while ultraviolet B (UV-B) or gamma irradiation decreased platelet responses. However, in alloimmunized lymphocytoxic antibody-positive patients, the immediate increment to UV-B-irradiated platelets was well maintained, whereas all other products showed substantial reductions. Refractoriness to platelet transfusions developed in 27% of the patients. Platelet refractoriness was associated with lymphocytotoxic antibody positivity, heparin administration, fever, bleeding, increasing number of platelet transfusions, increasing weight, at least 2 pregnancies, and male gender. The only factors that reduced platelet refractoriness rates were increasing the dose of platelets transfused or transfusing filtered apheresis platelets.

Figure 1.

Relationship between number of platelet transfusions and platelet increments at 1 hour and 18 to 24 hours after transfusion and days to next transfusion. (A) The mean 1-hour posttransfusion platelet increments are plotted for the first 25 transfusions given to all study patients. These data represent 6334 transfusions given to 533 patients (•). Similar data for the 18- to 24-hour posttransfusion platelet increments are shown for 5555 transfusions given to 531 patients (○). Data for days to next transfusion for 5955 transfusions given to 530 patients (▴). (B) When the same analyses are plotted for only lymphocytotoxic antibody-negative patients, the results are similar. One-hour increments for 5484 transfusions given to 477 patients (•), 18- to 24-hour increments for 4833 transfusions given to 475 patients (○), and days to next transfusion for 5144 transfusions given to 474 patients (▴). Dotted lines are best fit of the data for 1-hour posttranscription increments; dashed lines, for 24-hour posttransfusion increments; and solid lines, for days to next transfusion.

Figure 2.

Relationship between 1-hour posttransfusion platelet increment and platelet count of the transfused platelet concentrate for PCs, UVB-PCs, F-PCs, and F-APs. In each part of this figure, the 1-hour platelet increment is plotted versus the platelet count of the transfused platelet concentrate for control PCs (A), UVB-PCs (B), F-PCs (C), and F-APs (D). The equations for the regression lines are control PCs: 10.17 + 4.21 × dose × 10¹¹; UVB-PCs: 5.98 + 4.21 × dose × 10¹¹; F-PCs: 4.84 + 5.33 × dose × 10¹¹; and F-APs: 1.08 + 7.28 × dose × 10¹¹. The regression line for the control PCs is plotted as a dotted line in each panel for comparison with the regression line for the treated platelets shown as the solid line in panels B-D.

Figure 3.

Development of platelet refractoriness. The estimated percent of patients who will become platelet refractory is plotted against the time to become platelet refractory. Of the 528 patients analyzed, 143 (27%) became platelet refractory. By 17 days, 25% were estimated to become refractory, and this number would be projected to increase to 42% with continued platelet transfusions. There was no difference in the incidence of platelet refractoriness among the patients assigned to receive control PCs, UVB-PCs, F-PCs, and F-APs. Refractoriness was defined as 2 serial platelet transfusions with 1-hour posttransfusion platelet increments of less than 11.0 × 10⁹ platelets/L.