Blood is drawn in different standardized conditions through a glass bead filter. Platelet counts (electronic particle counter or phase contrast microscope) are performed before and after exposure of the blood to the glass surface. Platelet retention (P.R.) is expressed as the absolute number or, more commonly,as the percent of platelets which stick to the glass surface. The P.R. is calculated by dividing the difference of the platelet count before and after passage through the column by the initial value and expressed as a percentage.KeywordsGlass BeadPlatelet AdhesivenessVacutainer TubeMetal ConnectorPlastic HolderThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.