Comparison of Five Different Citrated Tubes and Their in Vitro Effects on Platelet Activation

After blood is collected in a tube, platelet activation occurs rapidly, hampering studies of other causes of platelet activation (1)(2)(3). Ideally, collection tubes for such studies have minimal activation potential. In vitro platelet activation has consequences for the evaluation of heparin activity as well (4) because activated platelets might release platelet factor 4 (PF4), inactivating heparin and leading to artifactual shortening of activated partial thromboplastin time (APTT) results.To evaluate platelet activation, markers appearing on the cell surface can be studied, as can the release of products from platelet α-granules. The purpose of this study was to evaluate the effect of blood sampling tubes on platelet activation. We compared five tubes: Because there is a 9:1 blood:citrate volume ratio in the tubes, the final citrate concentration after tubes are filled with blood is 0.0109 mol/L in all tubes except for tube 4, which has a final concentration of 0.0129 mol/L.We measured CD62, or P-selectin (GMP-140; PADGEM), which is a platelet α-granule protein expressed on the surface of platelets after activation and is used …