Myeloperoxidase
Myeloperoxidase (MPO) is an enzyme released by white blood cells during inflammation, where it generates reactive, oxidizing molecules. In cardiovascular testing, a blood MPO level is used as a marker of oxidative stress and inflammatory activity in the artery wall.
MPO is of interest because it may reflect not just inflammation but the vulnerability of plaque, its tendency to become unstable and rupture, which is what triggers many heart attacks and strokes. It is measured as an emerging way to add texture to cardiovascular risk beyond cholesterol numbers alone.
An elevated MPO can indicate heightened oxidative stress and inflammation and has been associated with more vulnerable, rupture-prone plaque and higher cardiovascular risk. Because MPO rises in many inflammatory states, an elevated result is a signal to interpret carefully with a clinician, not a stand-alone diagnosis.
A lower MPO level generally suggests less oxidative and inflammatory activity and is usually not a cause for concern on its own.
Lower is generally considered more favorable, with reference ranges varying by laboratory, but MPO is an emerging marker best interpreted by a clinician alongside your broader inflammatory and cardiovascular risk profile. It is a specialized test not included on routine panels and is typically used only to refine risk.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.