Antineutrophil Cytoplasmic Antibody in Lupus Nephritis: Correlation with Clinicopathological Characteristics and Disease Activity.

Background: Lupus nephritis (LN) represents 40%-50% of all systemic lupus erythematosus (SLE) patients, and rapidly progressive glomerulonephritis is associated with significant morbidity and mortality. Antineutrophil cytoplasmic antibody (ANCA) might be involved in the pathogenesis of LN.

Objective: We evaluated the role of myeloperoxidase (MPO)-ANCA, proteinase 3 (PR3)-ANCA, and anti-glomerular basement membrane autoantibodies (anti-GBM autoAb) for the diagnosis of LN.

Methods: In this cross-sectional study, 95 SLE patients were divided into 2 subgroups: LN group (n = 60) and non-LN group (n = 35). For further analysis, we subclassified the LN group into ANCA- positive (n = 16) and ANCA-negative (n = 44) LN patients. The entire Non-LN group was ANCA- negative. The SLE disease activity index (SLEDAI) was reported for each patient. Determination of MPO-ANCA, PR3-ANCA, and anti-GBM autoAb was performed using a novel multiplex bead-based technology in all patients. Data analyses were done using SPSS, version 20. Approval was obtained from the institutional review board of Zagazig University (ZU-IRB#6000).

Results: Of 95 patients with SLE, 16 patients (16.84%) had ANCA-positive LN, all of which were MPO-ANCA. There was a positive correlation between MPO-ANCA and SLEDAI, as well as with class IV LN. Receiver operating characteristic analyses revealed that the sensitivity and specificity of MPO-ANCA were 81.3% and 99.8%, respectively, in discriminating LN from systemic lupus without nephritis.

Conclusion: MPO-ANCA level was significantly correlated with SLEDAI, inflammatory markers, kidney function tests, and LN class IV.