Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1082 page)

   
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, et al. Heparins increase endothelial nitric oxide bioavailability by liberating vessel-immobilized myeloperoxidase.
Circulation
2006;113:1871–1878.

Peacock WF, Nagurney J, et al. 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, et al. Prognostic value of plasma myeloperoxidase concentration in patients with stable coronary artery disease.
Am Heart J.
2008;155(2):356–360.

MYOGLOBIN
*

   Definition

   Myoglobin is the primary oxygen-carrying protein of muscle tissues found only in skeletal and cardiac muscle. It is a small-sized molecule that is rapidly released from damaged tissue and is not protein bound and rapidly excreted in urine. Plasma half-life is 9 minutes. It is linked in a reversible manner with oxygen, playing an important part in cellular aerobic metabolism.

   
Normal range
(may be wide): 6–90 ng/mL.