The clinical value of monoclonal protein in ANCA-associated vasculitis with renal involvement.

PURPOSE: The value of monoclonal protein (M-protein) in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) patients with renal involvement has not been investigated. METHODS: We analyzed AAV patients with renal involvement from 2013 to 2019 in our center. Patients with immunofixation electrophoresis were divided into M-protein positive group and M-protein negative group. The clinicopathological features and outcomes of the two groups were compared. RESULTS: Ninety-one AAV patients with renal involvement were enrolled for analysis, and 16 patients (17.6%) had a positive test for M-protein. Compared with M-protein negative patients, M-protein positive patients had lower hemoglobin (77.6 vs 88.4 g/L, p = 0.016), mean corpuscular hemoglobin concentration (313 vs 323 g/L, p = 0.002),serum albumin (29.4 vs 32.5 g/L, p = 0.026) and complement 3 (C3) (0.66 vs 0.81 g/L, p = 0.047), while higher platelets (252 vs 201 109/L, p = 0.048) and incidence of pulmonary infection (62.5% vs 33.3%, p = 0.029). However, renal pathological features between the two groups had no significant difference. In addition, during a median follow-up of 33 months, Kaplan-Meier survival analysis showed that, compared with M-protein negative patients, M-protein positive patients had a higher risk of all-cause mortality (log-rank test, p = 0.028), especially for patients who were not dialysis-dependent at the time of admission (log-rank test, p = 0.012). CONCLUSION: Our results indicate that M-protein is associated with different clinicopathological features and increased all-cause mortality in AAV patients with renal involvement. Testing M-protein and rigorous diagnosing of the significance of the presence of M-protein may be helpful for assessing the survival of AAV patients with renal involvement.