ANCA positivity at the time of renal biopsy is associated with chronicity index of lupus nephritis

We investigated the association of antineutrophil cytoplasmic antibody (ANCA) positivity with lupus nephritis (LN) activity, histological features and prognosis in Korean patients with biopsy-proven LN having the results of both myeloperoxidase (MPO–ANCA) and proteinase 3 (PR3)–ANCA. We retrospectively reviewed the medical records of 91 LN patients having the results of ANCA. We divided patients with LN into the two groups according to the ANCA positivity. We collected clinical and laboratory data at kidney biopsy and histological features such as LN class including class I, II, III, IV-S, IV-G and V, and activity and chronicity index. We evaluated prognosis of LN during the follow-up by death and kidney failure. Twelve of 91 patients (13.2%) had ANCA at kidney biopsy. There were no differences in demographic data, comorbidities, reasons for kidney biopsy and laboratory data at kidney biopsy between patients with and without ANCA. In 12 LN patients with ANCA, Class III was the most frequently observed LN class (41.7%), while in 79 LN patients without ANCA, class IV-G was the most often detected LN class (35.4%). There were no meaningful differences in classes of LN between the two groups. On the other hand, patients with ANCA exhibited the higher median chronicity index than those without (2.5 vs. 1.0, P = 0.028), unlike activity index. ANCA positivity exhibited no association with death or kidney failure during the follow-up. ANCA positivity at kidney biopsy is associated with chronicity index of LN.