Assay

Myeloperoxidase (MPO) antibodies

Key Words

Myeloperoxidase antibodies, MPO, ANCA

Specimen Collection

Serum (Brown)

Turnaround time

10 days

Test indications

This is a confirmatory test for the presence of anti-MPO antibodies that are principally associated with a P-ANCA pattern seen on Indirect immunofluorescence. High-titre MPO with P-ANCA is associated with microscopic polyangiitis (MPA). In some cases Granulomatosis with Polyangiitis (GPA) (formerly known as Wegener’s granulomatosis) and Eosinophilic granulomatosis with Polyangiitis (EGPA) (formerly known as   Churg-Strauss syndrome).

P-ANCA positive- MPO-ANCA negative (or weak positive) results may occur in treated, inactive, or relapsing MPA (and its renal-limited variant), GPA and EGPA. Although can also be seen in inflammatory bowel disease and other autoimmune diseases where it’s clinical significance in unclear.

Patients with systemic vasculitis in whom ANCA reoccur are more likely to relapse.

High levels of MPO-ANCA are found in patients with some forms of drug induced SLE or vasculitis. These levels drop after the drug is withdrawn.

MPO antibodies are only tested in ANCA-positive samples (determined by indirect immunofluorescence).

Methodology

Enzyme immunoassay

Interferences

No known methodological interferences

Reference Range

Negative <3.5IU/mL

Equivocal 3.5-5.0IU/mL

Positive >5 IU/mL

Analytical error

Contact laboratory x8454

Reference change value

N/A