Low abundance evs
In the context where every cell (and even organelles) can create extracellular vesicles that are then released to the environment, detecting very low abundance species can be the only way to use them as diagnostic markers (see Extracellular vesicles as markers for prostate cancer, EVs can be used as ovarian cancer markers using EVs as biomarkers)
Some strategies focus on enrichment of specific subpopulations based on physicochemical traits (for example see: SEC is the second most popular EV enrichment method and Ultra centrifugations is the most popular EV enrichment method).
Besides enrichment, readout systems that have high-throughput and the ability to detect single-events can be a valuable tool to use EVs as biomarkers. See, for example: literature/202301141333 Comparing SiMoA and SP-IRIS.