1. A method for assessing changes in cardiovascular homeostasis, comprising: a. obtaining a whole blood from a test subject suspected of having a cardiovascular disorder, said whole blood specimen comprising a mixed cell population suspected of having target cells selected from the group consisting of endothelial cells, epithelial cells, and combinations thereof; b. contacting said whole blood specimen with a preservative capable of stabilizing said mixed population; c. mixing said whole blood specimen from step b with colloidal magnetic particles between 90 to 150 nm in size coated with stabilizing material and adapted to permit less than 0.3% non-specific binding and coupled to a monoclonal antibody which binds specifically to said target cells so as to capture the target cells, to the substantial exclusion of non-target cells; d. subjecting the specimen-magnetic particle mixture to a high gradient magnetic field to produce a separated cell fraction enriched in magnetic particle-bound target cells; and e. enumerating the target cells that are nucleated, CD146 positive, CD105 positive, and CD45 negative using multiparameter image cytometry wherein a change in the number of said target cells in comparison to predetermined normal control values from subjects having normal cardiovascular homeostasis provides indication of a change in cardiovascular homeostasis.