Elevated number of Circulating Endothelial Cells (CEC) have been implicated in disease conditions associated with the formation or destruction of blood vessels such as acute coronary syndrome, thrombocytopenic purpura, sickle cell disease, sepsis, lupus, nephrotic syndromes, rejection of organ transplants, surgical trauma and cancer. This invention provides a method for assessing the levels of CEC which vary between different studies using a sensitive enrichment, imaging, and enumberation analysis. CD146 is one of the most specific endothelium-associated cell-surface antigens which can be used in image cytometry. CEC analysis provides an essential tool in prognostic/diagnostic evaluation in the clinic.