A method of bioassay for the quantification of peptide fragments comprising a neo-epitope formed by cleavage of a protein of an atherosclerotic plaque by a proteinase, wherein the protein is versican and said method comprises contacting a sample such as urine or serum with an antibody reactive with the neo-epitope and determining the level of binding of said immunological binding partner to peptide fragments in said sample. The assay is predictive of risk of cardiovascular disease events.