The present invention relates to a cell culture system to provide a tool for assessing the potential of a patient's serum for preventing the accumulation of cholesterol in arteries (i.e. serum efflux potential) that leads to atherosclerosis and to screen new drug compositions being developed to reduce the accumulation of cholesterol or enhance the clearance of cholesterol from the vessel wall. The present invention combines two individual assays, which are two different cholesterol assays: an assay measuring scavenger receptor class B type I (SR-BI)-mediated cholesterol efflux and an assay measuring ATP binding cassette protein 1 (ABCA1)-mediated cholesterol efflux, and uses them in parallel to test human and animal sera for their potential to stimulate efflux, as mediated by either of the two receptors described above.