Pre-analytical conditions represent an important source of variability and potential artifacts in the analysis of microvesicles (MVs). The optimal measurement of circulating microvesicles necessitates cautions to avoid ex vivo MV generation and to obtain complete removal of platelets prior to enable storage.
It is commonly recommended to discard the first milliliters of blood to avoid the effects of the vascular damage caused by venipuncture. Sodium citrate is the most commonly used anticoagulant in hemostasis laboratories when collecting whole blood samples.
It is worth noting transporting blood tubes in a vertical rather than a horizontal position, via the use of special transportation boxes, limits the extent of in vitro MV generation.
The centrifugation conditions, speed and time vary widely among studies. The best efficiency in terms of platelet removal efficiency and stability after deep-freeze storage was demonstrated with 2x2500 g 15 min centrifugation protocol [Mullier et al.]
In most cases, samples must be stored prior to analysis, due to contradictory, but significant evidence in some laboratories regarding the impact of freeze–thaw cycle on MV measurements.
However, under the conditions where the platelets have been correctly depleted, no major impact of deep freezing has been described.