The present disclosure relates to a method for determining a risk factor indicative of predicted growth of an abdominal aortic aneurysm of a patient. The method comprises receiving at least one index of endothelial function of the subject； comparing the or each index of endothelial function with at least one of: a respective reference value； and a further index of endothelial function of the subject； and determining the index of aneurysm future growth based on the comparison. The or each index of endothelial function is indicative of a concentration of one or more circulating biomarkers of endothelial function and a previous aneurysm growth pattern of the subject.
