Assay

Proteinase-3 (PR3) antibodies

Key Words

Proteinase-3 antibodies, PR3, ANCA

Specimen Collection

Serum (Brown)

Turnaround time

10 days

Test indications

This is the confirmatory test for the presence of anti-PR3 antibodies in ANCA positive samples mostly associated with C –ANCA (Cytoplasmic staining pattern) on indirect immunofluorescence.

C-ANCA positive PR3 ANCA results occur are associated with Granulomatosis with Polyangiitis (GPA) (formerly known as Wegener’s granulomatosis), and can also occur in Microscopic Polyangiitis (MPA) (and its renal-limited variant), and Eosinophilic Granulomatosis with Polyangiitis (EGPA) (formerly known as Churg-Strauss syndrome). Patients with systemic vasculitis in whom ANCA recur are more likely to relapse.

C-ANCA positive- PR3 ANCA negative and MPO-ANCA negative results may occur in treated, inactive, or relapsing GPA, MPA and EGPA. It also occurs with chronic infections and occasionally in inflammatory bowel disease and other autoimmune diseases where its clinical significance is unclear.

PR3 antibodies are only tested in ANCA-positive samples (determined by indirect immunofluorescence).

Methodology

Enzyme immunoassay

Interferences

No known methodological interferences

Reference Range

Negative <2.0 IU/mL

Equivocal 2.0-3.0 IU/mL

Positive >3.0 IU/mL

Analytical error

Contact laboratory x8454

Reference change value

N/A