Myeloperoxidase (MPO) is an enzyme found in white blood cells that plays a crucial role in the body's immune defense system. This test measures MPO levels in the blood to assess inflammation and cardiovascular disease risk. MPO catalyzes the production of reactive oxygen species that help fight infections but can also cause tissue damage and promote inflammation. Elevated MPO levels are associated with increased cardiovascular disease risk, as MPO contributes to atherosclerosis by promoting inflammation, oxidative stress, and plaque instability. The test helps stratify cardiovascular risk into three categories: low risk (<470 pmol/L), moderate risk (470-539 pmol/L), and high risk (>539 pmol/L). This information can guide decisions about cardiovascular disease prevention and treatment strategies, particularly in patients with intermediate cardiovascular risk.