Adequate enrichment of extracellular vesicles in laboratory medicine

Abstract Extracellular vesicles (EVs) and their clinical applications have been recognized as one of the most fast‐growing and promising fields. Numerous groups including us have expressed their concerns on the idea of isolating “pure” EVs for different purposes, as there are no specific markers to date that can examine the exact EV purity. Typically, major instrument need and EV yielding loss are primary compensations of getting EVs with higher purity. As such, especially in biomarker‐based clinical tests, ceaseless efforts for obtaining more pure EV are worth of discussion. We here propose alternative philosophy to tone down the importance of purity, but to emphasize the significance in clinical laboratory medicine to measure EVs obtained by well‐controlled isolation methods. As a result, EVs are enriched to the adequate degree to meet certain clinical applications such as disease diagnosis and/or prognosis. In this review, we will justify the adequate enrichment rationale with advances of EV definitions, markers and contaminants, EV isolation methods, as well as the conclusions acquired from clinical research using less pure but ease‐to‐operate EV isolation methods.