Microparticles are now considered as critical effectors involved in numerous biological processes (coagulation, inflammation, and vascular biology). Microparticle can be measured using a quantitative and descriptive approach by flow cytometry (FCT) or by a functional approach assessing microparticle biological activities by a factor Xa-based clotting assay. FCT can be used to determine the cellular origin of the different microparticles, although there are concerns about the detection limit of this approach. Functional assays measure only the procoagulant activity of isolated microparticles and give no information on the cellular source or the physical properties of the microparticles. The advantage of the functional assays is that the assays use well defined reagents, and they are readily automated with high sensitivity and simplicity. In this study, we analyzed samples from 60 patients with active cancer of different type, 60 patients with a BMI more than 25 kg/m, and 49 carriers of Factor V Leiden with and without a prior venous thromboembolic episode. The study showed a significant correlation (P < 0.05) between microparticles determined by annexin V-microparticle-based FCT and a procoagulant activity-based clotting assay. This indicates that the procoagulant assay could be used as a routine screening test to screen out the normal samples so that only the abnormal samples need further testing by FCT.