COL4A1 and triple-A syndrome: To investigate whether degradation of COL4A1/A2 in AAA lesions results in release of circulating COL4A1/A2 fragments in AAA patients, we quantified two well-characterized COL4A1/A2 fragments in plasma samples from a nested case–control cohort of the VIVA screening trial (476 AAA patients and 200 age-matched controls)19 (Supplementary Table 1).