Myeloperoxidase (MPO), Plasma

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Subject: Myeloperoxidase (MPO), Plasma

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Definition

  • MPO is an enzyme stored in granules of PMNs and macrophages with primary anti-infective functions. It is released in plasma in inflammatory conditions and is thought to potentially play a role in CHD by oxidizing LDL and contributing to atherosclerotic plaque instability. MPO is elevated in angiographically proven CAD, acute coronary syndromes, and correlates with functional class in systolic heart failure.

  • Normal range: <539 pm in healthy individuals.

Use

  • Marker of inflammation when elevated in plasma. MPO may be used for the evaluation of patients presenting with acute chest pain, in conjunction with ECG and cardiac biomarkers.

Interpretation

  • An initial increase independently predicts risk of myocardial infarction and adverse cardiac events and predicts sudden death in the next 1–6 months, even in the absence of signs of ischemic necrosis or of increase in other inflammatory markers, such as CRP. A low MPO improves the negative predictive value of normal troponins in unstable angina. At present, there is conflicting evidence for the additive diagnostic utility of MPO above established cardiac biomarkers in acute chest pain patients, and it is not recommended for routine triage of ACS.

  • Elevated plasma MPO concentration is associated with a more advanced cardiovascular risk profile; however, plasma MPO does not predict mortality independent of other cardiovascular risk factors in patients with stable coronary artery disease.

Limitations

  • It has been demonstrated that elevations of MPO can occur with the administration of heparin products, potentially confounding its accuracy.

  • Elevated in rheumatoid arthritis.

Suggested Readings

Baldus  S, Rudolph  V, Roiss  R Heparins increase endothelial nitric oxide bioavailability by liberating vessel-immobilized myeloperoxidase. Circulation  2006;113:1871–1878.
Peacock  WF, Nagurney  J Myeloperoxidase in the diagnosis of acute coronary syndromes: The importance of spectrum. Am Heart J.  2011;162:893–899.
Stefanescua  A, Braun  S, Ndrepepa  G Prognostic value of plasma myeloperoxidase concentration in patients with stable coronary artery disease. Am Heart J.  2008;155(2):356–360.
 
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