MFAP4 and Marfan syndrome: In addition to its expression in the aortic ECM, MFAP4 was detectable in plasma obtained from a subset of patients with MFS from the COMPARE trial (n=96).21 To determine whether plasma MFAP4 associates with aortic events, the 96 patients with MFS were subdivided into 3 equal tertiles (lower, middle, and upper tertile) based on their MFAP4 protein levels.