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Lupus nephritis (LN) is a prevalent and severe systemic lupus erythematosus (SLE) complication, affects 40-70% of patients, leading to increased morbidity and mortality. Identifying prognostic markers and understanding treatment response are critical. The objective of this study was to evaluate the response to immunosuppressive treatment in LN patients, assess proteinuria, complement levels of C3 and C4 at the third, sixth, and twelfth months of therapy, and correlate these findings.
This was an observational, retrospective study. It was conducted on LN patients. These patients were evaluated in the induction
phase of Therapy. The study was conducted at the Nephrology Department of the Hospital Federal de Bonsucesso, RJ. Patient records from 2016-2021 were analyzed. We evaluated epidemiological data, C3 and C4 levels, and proteinuria values before and after starting therapy. We included patients over 18 years with LN proven by renal biopsy, class IV or V.
We evaluated 24 patients with Class IV or V LN, mean age 36 years, 23 females. Thirteen used mycophenolate mofetil (MM), 9 used intravenous cyclophosphamide (CFH), and 2 used other treatment regimens in addition to CFH. Low C3 and/or C4
levels were observed in 50% (12/24) of the patients at admission. Complete remission was observed in 5 patients after 3 months, 7 patients after 6 months and 13 patients after 12 months of treatment. All patients with complete remission after 12 months of treatment exhibited normal complement levels, correlating with proteinuria reduction. Partial remission was observed in 7 out of 24 patients after treatment. Patients showing partial remission maintained low C3 levels throughout the treatment (3 out of 7). Additionally, the study found a significant linear relationship between C3 levels and proteinuria with a coefficient of -15.51 (p-value: 0.008). There was also a significant logarithmic relationship between ln(C4) and ln(proteinuria), indicating that for a 1% increase in C4, proteinuria is expected to decrease by approximately 0.4783% (p-value: 0.014).
There is a known correlation between disease activity and low complement levels in lupus. However, some patients, even with significant prteinuria, have normal levels of these markers, regardless of the class of nephritis. The correlation between proteinuria and markers of the complement system should be studied further, for better targeting and better therapeutic response. This study showed a linear correlation of C3 with proteinuria and a logarithmic correlation with C4 levels.