Standardization of Blood Collection and Processing for the Diagnostic Use of Extracellular Vesicles

Purpose of Review Extracellular vesicles (EVs) are lipid membrane vesicles released by many types of cells in both health and disease. EVs can be found in most body fluids, carrying a plethora of biomolecules, including proteins, RNA, and DNA, that reflect the biomolecular composition of the tissue of origin. Parenchymal and stromal cells actively release EVs in the extracellular milieu and in circulation, providing valuable information that may be exploited for diagnostic applications. However, isolation of these EV subpopulations in circulation is extremely challenging as they are diluted within more abundant EV subpopulations derived from blood cells (red blood cells, platelets, and white blood cells). Recent Findings A number of preanalytical variables during blood collection and processing greatly impact the levels of blood-derived EVs, thus affecting sample quality. So far, lack of standard protocols for blood collection and processing as well as quality control metrics has limited the clinical validation and adoption of EV-based diagnostic assays. Summary In this review, we describe the preanalytical variables that affect sample quality and suitability for EV-based diagnostic approaches. Furthermore, we suggest biochemical and molecular quality control (QC) metrics to minimize intra- and interstudy variability and improve data robustness and reproducibility.