: Myeloperoxidase Antibody, Serum

: What Is Being Tested

: Myeloperoxidase (MPO) is an enzyme stored in the granules of neutrophils, a type of white blood cell. This test measures antibodies in the blood (serum) that target MPO. The presence of these antibodies can indicate that the immune system is mistakenly reacting against this enzyme.

: Why the Test Is Ordered

: Your clinician may order this test when there are signs of inflammation in small blood vessels, such as kidney, lung, skin, or nerve problems. It is commonly used alongside other antibody tests, including ANCA testing, to help classify and monitor certain autoimmune conditions.

: How the Test Is Performed

: A blood sample is collected from a vein, usually in the arm, and sent to the laboratory. There, an immunoassay method is used to detect and measure MPO antibodies in the serum. No special preparation is typically required unless your clinician advises otherwise.

: What the Results Mean

: A positive result suggests that MPO antibodies are present and may support a diagnosis of an MPO-associated small-vessel vasculitis, but results must be interpreted together with symptoms, physical findings, and other tests. A negative result makes this condition less likely but does not rule it out entirely. Your clinician will explain what your specific result means for you.