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

The value of monoclonal protein (M-protein) in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) patients with renal involvement has not been investigated.

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.

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).

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.