DETERMINATION OF THE RATE OF REDUCTION IN PLATELET COUNTS IN RECIPIENTS OF HEMATOPOIETIC STEM AND PROGENITOR-CELL TRANSPLANT - CLINICAL IMPLICATIONS FOR PLATELET TRANSFUSION THERAPY

BACKGROUND: To investigate how a delay between pretransfusion platelet count measurement and actual platelet transfusion affects the assessm ent of platelet transfusion responses, the rate of reduction in platel et counts was determined in 30 patients with relatively uncomplicated thrombocytopenia. STUDY DESIGN AND METHODS: Fifteen adult and 15 pedia tric patients admitted for hematopoietic stem and progenitor cell tran splantation were studied. Platelet counts before and after myeloablati ve conditioning and after prophylactic platelet transfusions were dete rmined and studied as a function of time. The rates of reduction in pl atelet counts were determined by linear regression analysis. RESULTS: Platelet counts were reduced at linear rates after myeloablative condi tioning or prophylactic platelet transfusion in all 30 patients. The a verage rates of reduction in platelet counts after myeloablation were 1261 +/- 583 and 1070 +/- 492 platelets per mu L per hour (mean +/- SD ) for adult and pediatric patients, respectively. The average rate of reduction after platelet transfusions during the thrombocytopenic phas e was 740 +/- 280 and 820 +/- 288 platelets per mu L per hour (mean +/ - SD) for adult and pediatric patients, respectively. The rates of red uction in platelet counts between the two phases were significantly di fferent in the two age groups (adult, p<0.0001; pediatric, p<0.015) an d were proportionally correlated with initial platelet counts immediat ely before myeloablation and after prophylactic platelet transfusions. CONCLUSION: The rate of reduction in platelet count can have a signif icant impact on the evaluation of platelet transfusion responses when there is a delay between pretransfusion measurement of platelet count and the initiation of platelet transfusion. In addition, the rate of p latelet reduction determined from this study can be used to confirm an accelerated rate of platelet consumption in thrombocytopenic patients .