Abstract: FR-PO0655
Serum Proteinase 3 Antibody Titers in Primary vs. Secondary ANCA-Associated Glomerulonephritis
Session Information
- Glomerular Diseases: Clinical, Outcomes, and Therapeutics Research - ANCA/FSGS
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Peel, Nathaniel F., The University of Queensland Faculty of Medicine, Herston, Queensland, Australia
- Shaw, Analee, The University of Queensland Faculty of Medicine, Herston, Queensland, Australia
- Ren, Alison Li, The University of Queensland Faculty of Medicine, Herston, Queensland, Australia
- Zarm, Ayaa M., The University of Queensland Faculty of Medicine, Herston, Queensland, Australia
- Velez, Juan Carlos Q., The University of Queensland Faculty of Medicine, Herston, Queensland, Australia
Group or Team Name
- Ochsner Nephrology
Background
Anti-neutrophilic cytoplasmic antibody (ANCA) production is the hallmark of Primary ANCA-associated vasculitis. However, infections and drugs can induce ANCA-driven autoimmunity. In glomerulonephritis (GN) associated with ANCA, the ANCA subtype has been claimed as indicative of the underlying diagnosis. Thus, we examined the relationship between the subtype of ANCA [myeloperoxidase (MPO) and proteinase 3 (PR3)] and the underlying cause of ANCA-GN.
Methods
We utilized a prospective data collection platform for adult patients seen for nephrology consultation for evaluation of AKI and/or hematuria/proteinuria who completed urinary sediment microscopy (uSEDI) over a 7-year period. MPO and PR3 ANCA titers were extracted. Primary ANCA GN was defined as presence of: 1) detectable ANCA, 2) biopsy-proven pauci immune GN or uSEDI with acanthocytes/RBC casts, and 3) absence of either infective-endocarditis (IE), cancer or drug exposure associated with ANCA vasculitis. IE-associated GN (IEGN) cases were also extracted, as well as ANCA-GN associated with drugs (DI-ANCA-GN), namely hydralazine (HYDRZ) and cocaine/levamisole (COC/LEV).
Results
A total of 57 patients were included. In Primary ANCA-GN (n = 32; median age 66, 44% women), 21 (65%) were MPO+ (range 15->134 U/mL), 10 (31%) were PR3+ and 1 (3%) was double MPO/PR3+. In IEGN (n = 19; median age 37, 50% women), 8 (42%) were PR3+ (range 1.0->8.0 U/mL) and the organism was Enterococcus faecalis in 3, Bartonella henselae in 3 and Streptococcus mutans in 2. In DI-ANCA-GN (n = 6, 5 HYDRZ, 1 COC/LEV) 4 were double MPO/PR3+ and 2 MPO+. When comparing serum anti-PR3 titers, Primary ANCA-GN was associated with higher titer (median >8.0 U/mL) compared to IEGN (median 3.5 U/mL) and DI-ANCA-GN (0.5 U/mL), p=0.0034 for ANOVA. Serum anti-PR3 above the upper limit of normal (>8.0 U/mL) was seen in 8/10 (80%) of Primary ANCA-GN but also in 3/8 (40%) of PR3+-IEGN cases.
Conclusion
IEGN associated with ANCA presents exclusively as PR3+ in non-Staphylococcus IE and most commonly with low serum titers. Although high PR3 titer is more common in Primary ANCA-GN, it can be found in IEGN, thus, high PR3 titer should not negate search for a cardiac vegetation. MPO-ANCA is mainly seen in Primary ANCA-GN but also in DI-ANCA-GN, although often manifested as double MPO/PR3+ for the latter.