Standardization of pre-analytical variables in plasma microparticle determination: results of the International Society on Thrombosis and Haemostasis SSC Collaborative workshop

Abstract

Microparticles (MP) are sub-micron sized vesicles released by activated or apoptotic cells. They are generally defined as 0.1 to 1 μm membrane particles that expose the anionic phospholipid phosphatidylserine (PS) and membrane antigens representative of their cellular origin [1]. It is now well recognized that MP behave as vectors of bioactive molecules, playing a role in blood coagulation, inflammation, cell activation and cancer metastasis. In clinical practice, circulating MP originating from blood and vascular cells are elevated in a variety of prothrombotic and inflammatory disorders, cardiovascular diseases, autoimmune conditions, infectious diseases and cancer [1-3]. © 2013 International Society on Thrombosis and Haemostasis.

Fig. 1

Impact of the pre-analytical protocol on the inter-individual and inter-laboratory variability of MP measurements (A & B). Impact of pre-analytics on inter-individual variability of PMP counts by FCM. PMP counts by FCM in normal plasma samples prepared by different laboratories using a common pre-analytical protocol (protocol A, upper graph) or their in house pre-analytical approach (protocol B, lower graph). Median (dashed line) and 25–75% interquartile range (dotted lines) of PMP using protocol A. For example, 1A means laboratory number 1, protocol A. ‘All’ accounts for the combination of data from all the laboratories. (C). Impact of pre-analytics standardization on interlaboratory variability of PMP counts and procoagulant activities. To determine if the inter-laboratory variability was different between protocols for each analyzed parameter, the coefficient of variation was calculated for each laboratory. Then a mean coefficient of variation was derived by averaging all coefficients related on a parameter. Differences between protocols were evaluated used the Bootstrap method and expressed by determination of the confidence intervals. The normal approximations method has been used for computing 95% confidence intervals. CV, coefficient of variation; CI, confidence interval determined by the Boopstrap method (vertical bars).