Myeloperoxidase Stain

Also known as: MY PEROX

Clinical Use

Use

The myeloperoxidase staining is helpful in differentiating myeloid leukemias. This test is used primarily to determine the myeloid lineage in acute myeloid leukemia (AML) per the WHO classification. It helps in recognizing certain subtypes of leukemia where myeloperoxidase positive granules are present in specific cells such as myeloblasts, promyelocytes, myelocytes, metamyelocytes, neutrophils, eosinophils, and monocytes. Monocytes stain diffusely and with less intensity compared to neutrophils and eosinophils. However, it is less sensitive and specific than flow cytometry immunophenotyping and its results must be interpreted within the clinical context. This test alone should not be used to establish a diagnosis.

Special Instructions

Not provided.

Limitations

The test has limitations in terms of sensitivity and specificity compared to flow cytometry methods. It cannot be used as a standalone diagnostic tool for leukemia, particularly because the intensity of staining can vary among myeloid cells. The cytochemical nature of the stain may miss some acute myeloid subtypes with less conspicuous peroxidase activity, and it does not detect peroxidase deficiencies. Additionally, its utility may be impacted by improperly prepared or aged samples beyond the recommended time frames, particularly for smears and non-ambient conditions.

Test Details

New York Approved

Methodology

Cell-based / Cytometry (Cytochemical Stain)

Biomarkers

Myeloperoxidase Activity

Analyte

MPO Staining

Expression • Categorical (e.g., Positive / Negative / Indeterminate)

LOINC Codes

Result Codes

32817-9 - Myeloperoxidase Spec

Result Turnaround Time

1-5 days

Specimen

Whole Blood

Volume

5 mL

Minimum Volume

Not provided

Container

Lavender (EDTA) or green (sodium or lithium heparin) or heparinized aspirate of bone marrow

Collection Instructions

Transport 6 unfixed, air-dried, and unstained push smears AND 5 mL whole blood (smears should be made from the blood submitted). OR 6 unfixed, air-dried, and unstained bone marrow aspirate smears.

Storage Instructions

Room temperature. Testing must be performed within 48 hours of collection.

Causes for Rejection

Frozen specimens. Peripheral blood smears older than one week. Anticoagulated blood or bone marrow sent without well-prepared unfixed smears if greater than 48 hours old.