Detection and measurement of microparticles: an evolving research tool for vascular biology.

Microparticles are small, membrane-bound vesicles that are generated from cells of different origin. It now appears that all circulating blood cells as well as endothelial cells release membranous fragments ~1 mum in size or smaller bearing at least some characteristics of the parent cell. Elevated levels of microparticles have been described in cardiovascular states, thrombotic conditions, and cancer. Various methods of detection for microparticles include flow cytometry, enzyme-linked immunoassays, and functional assays. Flow cytometry has several advantages including its ability to quantitate and identify microparticles of different cellular origin. However, the standardization of preanalytical and analytical variables for enumeration of microparticles remains a significant challenge. Newer approaches are being investigated, and an international collaboration is working on standardization of detection as well as quantitation of microparticles by flow cytometry. Although it has evolved as an important vascular biology research tool, microparticle detection needs further evaluation and refinement before it becomes truly useful as a clinical tool.