Abstract: The invention relates to a process for preparing antigen fractions designed for the detection of antibodies, the presence of which, in a certain quantity, in the human blood serum correlates with a cardiovascular risk condition. An arterial tissue is ground, freed of lipids and is subjected to the action of at least one agent selected from the group formed by an aqueous solution of an alkali metal salt or of an alkaline-earth metal salt at ambient temperature, of a hot acid of urea, of guanidine and proteolytic enzymes. The invention also relates to antigen fractions thus obtained and their utilization in the diagnosis of a cardio-vascular risk condition by counter-current electrophoresis or by an ELIFA test or an ELISA test.