Apo(a) contains a variable number of kringle-IV-type 2 repeats, which have prompted concerns about conventional Lp(a) assays.14 Novel MS assays that quantify peptides from the Apo(a)-constant region [Apo(a)-CR] at the Apo(a) C-terminus and the Apo(a)-kringle-IV-type 2 repeat region [Apo(a)-KR] and are independent of Apo(a) molecular mass have recently been developed, but their relationships with CHD risk are uncertain. Here, AOPEP is linked to coronary artery disorder.