Myeloperoxidase
Overview
Myeloperoxidase measures an enzyme stored in azurophilic granules of neutrophils and monocytes that generates hypochlorous acid and other reactive oxygen species for microbial killing during inflammation. It contributes to oxidative tissue damage in atherosclerosis, vasculitis, and acute coronary syndromes through endothelial dysfunction and plaque instability. Elevated levels indicate neutrophil activation in cardiovascular disease, inflammatory conditions, or infection; low levels lack clinical significance. Clinically, myeloperoxidase testing identifies patients at high risk for cardiovascular events and monitors inflammatory vasculitides.
Clinical Use Cases
- Risk stratification in acute coronary syndrome beyond troponin.
- Diagnosing and monitoring ANCA-associated vasculitides (microscopic polyangiitis, granulomatosis with polyangiitis).
- Assessing cardiovascular risk in stable coronary artery disease.
- Evaluating neutrophil activation in severe infections or sepsis.
Specimen Types
- Plasma (EDTA preferred).
- Serum.
Measurement Methods
- Enzyme-linked immunosorbent assay (ELISA).
- Chemiluminescent immunoassay.
- Latex-enhanced immunoturbidimetry.
Test Preparation and Influencing Factors
- No fasting required; avoid prolonged tourniquet application.
- Cigarette smoking, renal impairment, or active infection elevate levels.
- Corticosteroids and statins lower myeloperoxidase concentrations.
- Sample hemolysis interferes with immunoassay results.
Synonyms
- MPO.
- Myeloperoxidase antigen.