Function of platelets in apheresis platelet concentrates and in patient blood after transfusion as assessed by Impact‐R

BACKGROUND: Platelet (PLT) transfusion is a mainstream therapy for preventing or treating bleeding episodes in patients with thrombocytopenia. The efficacy is usually estimated from the corrected count increment of PLTs after transfusion, which does not assess PLT function. We therefore evaluated PLT function in blood samples of patients with thrombocytopenia before and after transfusion. STUDY DESIGN AND METHODS: PLT function was assessed in 24 chemotherapy‐treated patients and in the PLT concentrates (PCs) by the Impact‐R (DiaMed). This device evaluates PLT adhesion and aggregation recorded as surface coverage (%) and size of aggregates (AS µm²). P‐selectin expression was determined by flow cytometry. RESULTS: The PCs were stored for a median of 70 hours before transfusion. An analysis stratified by the median storage of PCs (<70 hr or >70 hr) showed no differences in the SC, the AS, and P‐selectin expression between these concentrates' groups. Transfusion resulted in an increase of adhering PLTs in the patients after transfusion. There were no differences in the AS and in P‐selectin expression before and after transfusion, but the AS increased after transfusion upon ex vivo exposure to adenosine 5′‐diphosphate. P‐selectin expression was significantly lower in the patient group receiving PCs stored for more than 70 hours. CONCLUSION: The current trial shows the feasibility of using the Impact‐R to assess the function of transfused PLTs in the patient's blood stream.