Platelet tracking in patients who received multiple platelet transfusions. The counts of patients’ endogenous (red), and transfused (colored according to the order of transfusion) platelets on each day before and after the transfusion are presented. (A) A patient received 2 platelet transfusions. An increase in patient endogenous platelets was observed from day 5. (B) A patient received 5 platelet transfusions. A sustained decrease in patient endogenous platelets without recovery during the follow-up period was observed. (C) A patient received 5 platelet transfusions within a week. Multiple units of transfused platelets could be discriminated using the method (days 5 and 6).