Summary Background: Platelet transfusions are effective for the prevention and treatment of bleeding in patients with disorders of platelet number and/or function. In recent years plateletpheresis concentrates have outnumbered pooled platelet concentrates, albeit with significant differences between nations. Thus, the platelet quality of individual donors has become increasingly important. The aim of this study was to gain an estimate for the prevalence of impaired platelet function among platelet donors. Study design and methods: We determined the inter-donor variability in platelet plug formation with a PFA-100 analyzer, the prevalence of impaired thromboxane formation, and effects of the density in alpha2 integrin polymorphism and density. Results: (i) Collagen-epinephrine induced closure time (CEPI-CT) showed a great inter-subject variability in platelet donors and was higher than in healthy controls (p = 0.008). One-fifth of donors had abnormal CEPI-CT values and 11% exceeded >300 s (max measurable value). (ii) Decreased serum thromboxane B2 levels were found in 9% of all donors, compatible with surreptitious intake of cyclooxygenase inhibitors or with an aspirin-like defect. CEPI-CT correlated inversely with TxB2-levels in donors and controls. (iii) The density of the alpha2-integrin correlated negatively with CEPI-CT and CADP-CT values in controls, but was not responsible for the observed impaired platelet function in donors. (iv) Finally, the ABO blood group system modulates closure times. Conclusion: In sum, a large number of platelet donors present with prolonged closure times. Decreased thromboxane formation and frequent platelet donation partly account for this observation. Abbreviations: 807 CC/CT/TT polymorphisms of the alpha2-integrin gene, CD36… GPIIIb, an alternative collagen receptor, CD42b… GpIb, the von Willebrand receptor, CD49b… alpha2-integrin, subunit of the main collagen receptor, CADP-CT… collagen adenosine diphosphate induced closure time, CEPI-CT… collagen/epinephrine induced closure time, PFA-100… platelet function analyzer, vWF-Ag… von Willebrand factor antigen, TXB2… thromboxane B2

SNP does not decrease platelet activation during apheresis and subsequent storage, and only a minor proportion of activated (p-selectin+) platelets circulate after transfusion in men. Moreover, biotin labeling of PCs can safely be used in humans for the study of platelet recovery after transfusion, and measuring recovery at 1 hour may lead to an underestimation of the true recovery when activated platelets are transfused.

Resuspension of platelets in Intersol for 7 days results in increased platelet activation and platelet metabolism compared with SSP+® or Composol®. Further clinical studies are needed to evaluate whether the observed differences in PAS-PCs affect the recovery rate or the life span of transfused platelets.

BACKGROUND: Platelet (PLT) collection and storage affect the functional capacity of PLTs in PLT concentrates (PCs). Therefore, PLTs' functional quality should be studied before transfusion. STUDY DESIGN AND METHODS: PCs (n = 15) were collected by a standard apheresis procedure (Trima, Gambro BCT) and were stored for 7 days. Samples were taken to assess PLT adhesion and aggregate formation by a cone and plate analyzer (Impact-R, DiaMed) on Days 1, 3, 5, and 7 after harvesting. This device allows testing PLT function under high-shear stress close to physiologic conditions. Concomitantly, P-selectin expression and the residual responsiveness to TRAP-6 were determined by flow cytometry. RESULTS: PLT adhesion, as measured by surface coverage, decreased during the entire observation period; likewise, the size of aggregates was significantly lower on Days 5 and 7 compared to Day 1 (p < 0.02). P-selectin expression increased from Day 5 to Day 7 (p < 0.04), whereas TRAP-6-inducible expression remained stable until Day 5 of storage and decreased significantly on Day 7 (p = 0.04). CONCLUSIONS: Our results show that high-shearinduced PLT adhesion and aggregation on the polystyrene surface deteriorate upon storage, suggesting decreased PLT function in vivo. Thus, the Impact-R may be a useful tool to assess the functional capacity of PLTs under various PLT harvesting and storage procedures. P latelet (PLT) transfusions are used to prevent or treat bleeding episodes in patients with thrombocytopenia, for example, after high-dose chemotherapy. The process of PLT collection and storage may affect the functional capacity of PLTs in PLT concentrates (PCs). Therefore, a variety of in vitro methods have been extensively investigated for their validity and feasibility to test and guarantee the function of PLTs that were prepared for their transfusion.1 Results from in vitro tests were correlated with the corrected count increment (CCI) of PLTs 1 or 24 hours after transfusion to estimate the validity of these tests clinically. 2-4Although the CCI is most often used to estimate the success of PLT transfusions, it does not always correlate with PLT survival.1 Very few in vitro tests performed on PLTs from PCs, however, correlate with PLT viability after their transfusion to healthy individuals, 4,5 and these tests have not been further validated after transfusion to thrombocytopenic patients. Further, the CCI does not evaluate PLTs' hemostatic activity. Thus, in vitro evaluation of PLT function in PCs is desirable before transfusion. According to the European guidelines, only the pH must be measured (6.4-7.4) and the swirling phenomenon must be demonstrated after 5 days of storage. This device allows evaluation of PLT function under close to physiologic conditions in a whole-blood assay. PLT adhesion and aggregation can be determined in anticoagulated blood under arterial flow conditions wherein a cone and plate viscometer induces laminar flow with a uniform shear stress over a plastic plate by the rotating cone. Results can then be e...

Inlet-line diversion decreased bacterial contamination during two-arm collections by more than 46%. Concurrently, doubling the sample volume was associated with a 54% relative increase in culture sensitivity. These interventions act cooperatively to decrease bacterial risk.