Myeloperoxidase Deficiency Workup

Updated: Oct 19, 2016
  • Author: Maureen M Petersen, MD; Chief Editor: Harumi Jyonouchi, MD  more...
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Workup

Laboratory Studies

The presence of myeloperoxidase (MPO) can be determined using numerous techniques, including histochemical staining, immunocytochemistry, and flow cytometry. Depending on the assay used, one must ensure that eosinophilic peroxidase (EPO) from eosinophils does not cause false-positive results. [15]

The easiest technique is to perform direct visualization of neutrophils on a peripheral blood smear that has been stained for peroxidase. The clinician can ask the pathologist to examine the neutrophils for peroxidase when a peripheral smear is requested. [16]

Dihydrorhodamine 123 (DHR) assay, a flow cytometric assay, is often used to measure the presence of reactive oxygen intermediates in the work-up of a patient with suspected immunodeficiency. This assay is easier, more reliable, and more sensitive than nitroblue tetrazolium dye reduction assay in the diagnosis of chronic granulomatous disease (CGD). At this time, a DHR assay should not be used as a screen for MPO deficiency because of variable results and poor sensitivity in detecting partial MPO deficiency. If a DHR assay is consistent with a diagnosis of CGD but the clinical history is more consistent with MPO deficiency, further laboratory testing should be performed (eg, genetic sequencing or intracellular staining with anti-MPO antibody). [17]