Start Date
Expiration Date
MPO/PR-3 IgG Antibodies, Proteinase-3 (PR-3)/Myeloperoxidase (MPO) IgG Antibodies
CPT Codes
83516 x 2
Reference Test
ATLAS Test Code

Specimen Information


Gold, SST


0.5 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Refrigerated 48 Hours
If specimen will not be received within 48 hours of collection, freeze serum and transport frozen

Fasting Required?
Patient Instructions

Reference Range

80-90% of c-ANCA samples have reactivity to PR-3 and 80-90% of P-ANCA samples have reactivity to MPO
Test results for MPO and PR-3 IgG antibodies should be interpreted in conjunction with the clinical evaluation and the results of ANCA testing


Enzyme-Linked Immunosorbent Assay (ELISA)

Clinical Significance

The test is part of the anti-neutrophil cytoplasmic antibodies (ANCA) reflex panel and is used to confirm all the ANCA positive specimens for MPO and PR-3 IgG antibody status
The clinical value of ANCA has been studied most in patients with Wegener's granulomatosis (WG) or WG variants, as well as those with microscopic polyangiitis (MPA). In patients with WG, there is a close association with the presence of c-ANCA. The association is strongest in patients with generalized disease, but the sensitivity decreases with localized or inactive disease states. Although the specificity of c-ANCA for WG was originally thought to be very high, c-ANCA and antibody to PR3 can be found in patients without classic WG. An example is idiopathic necrotizing and crescentic glomerulonephritis (NCGN), in which a small percentage of patients will have antibody to PR3. NCGN is generally considered to be a renal-limited form of MPA, although some patients will evolve into WG.MPA is often ANCA-positive with approximately an equal distribution of c-ANCA and p-ANCA, and no clear clinical distinction between the two. As with cases of NCGN, however, some MPA patients with antibody to PR3 will evolve into WG. Churg-Strauss syndrome shares with MPA an association with MPO antibody. From a therapeutic standpoint, numerous reports indicate that effective treatment of WG is associated with falling ANCA titers. The usefulness of monitoring titers in patients in remission, however, is controversial. Some authors have shown that rising titers in these patients are predictive of imminent (months) relapse. This has led some to recommend that an elevated ANCA, in the absence of overt clinical disease, should result in prompt reinstatement of immunosuppressive therapy. Not all patients, however, with rising titers will relapse and, in some cases, the relapse does not occur for several months after the ANCA determination. Careful consideration of the value of ANCA in this setting is advised due to the known side effects of aggressive immunosuppressive treatment.