To examine how apolipoprotein profiling could be used to quantify the residual risk of CHD, using stable isotope-labeled standards, we expanded a targeted mass spectrometry (MS) assay17 to include 13 apolipoproteins for the 4 main lipoproteins: (1) Lp(a)-related [Apo(a)-KR, Apo(a)-CR]; (2) LDL-related (ApoB); (3) triglyceride-related (ApoC1, ApoC2, ApoC3, and ApoE); and (4) HDL-related (ApoA1, ApoA2, ApoA4, ApoD, ApoH, ApoL1, and ApoM). The gene discussed is APOA4; the disease is coronary artery disorder.