Myeloperoxidase (MPO)
An enzyme released by certain white blood cells that generates powerful oxidants. In the blood vessels it promotes inflammation and oxidative damage that destabilise atherosclerotic plaque, so it is studied as a marker of vascular inflammation and cardiovascular risk, used as an adjunct rather than a routine test.
What it measures
Myeloperoxidase (MPO) is an enzyme stored in and released by neutrophils and monocytes, the white blood cells of the immune system. Its normal job is antimicrobial — it produces reactive oxidants that help kill bacteria. In the setting of atherosclerosis, though, this same oxidative activity works against the artery: MPO promotes inflammation, oxidises LDL cholesterol, reduces the protective function of HDL, and contributes to making atherosclerotic plaque unstable and more likely to rupture. Because of this, blood MPO has been studied as a marker of vascular inflammation and cardiovascular risk, including in people presenting with chest pain, where a raised level has been linked to a higher risk of adverse cardiac events. It is an adjunct marker rather than a standard test: it is used, where available, to add information to a risk assessment, alongside markers like hs-CRP and Lp-PLA2. Because MPO comes from white blood cells, it can also rise with infection and other inflammatory conditions, so it is interpreted in context and not used in isolation.
What a high value can mean
- Increased vascular inflammation and oxidative stress — linked to higher cardiovascular risk and more unstable plaque.
- In chest-pain assessment — associated with a higher risk of adverse cardiac events (an adjunct, not a diagnostic, use).
- Active infection or inflammation — because MPO comes from white blood cells, non-cardiac inflammation can raise it.
What a low value can mean
- Lower vascular inflammatory activity — generally reassuring in a cardiovascular-risk context.
- Normal — the expected result outside significant inflammation.
When to discuss with a doctor
Myeloperoxidase is a specialised, adjunct marker of vascular inflammation, not a routine or standalone diagnostic test. In cardiovascular risk assessment it can add information to markers such as hs-CRP and Lp-PLA2 and the standard lipid picture, and it has been studied in the assessment of chest pain — but it does not diagnose or rule out a heart attack, and chest pain always needs urgent clinical evaluation in its own right. Because it also rises with infection and other inflammation, a high level is interpreted alongside the whole picture rather than acted on alone. Mediora.AI shows MPO with the other inflammation and lipid markers so it is read in context; the interpretation and any action belong with your doctor.