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Systemic lupus erythematosus is a multi-organ disease with a high predilection for kidneys. The complement system has been described as a marker of disease activity, and within the approach to glomerulonephritis, complement consumption is assumed to exist. There are no studies in Latin America that describe outcomes related to complement consumption in patients with confirmed lupus nephritis through biopsy.
A retrospective case-control study of 38 patients with SLE and biopsy-confirmed lupus nephritis was conducted. Patients were divided into three groups based on C3 and C4 levels: low C3, low C4, and low C3 and C4. Clinical and sociodemographic data were collected and analyzed using descriptive and inferential statistical tests. The association between the three patient groups and the different clinical variables, including in-hospital death or initiation of renal replacement therapy was analyzed.
83 renal biopsies were reviewed, identifying 38 patients with lupus nephritis, 10.5% class III, 57.8% class IV and 31.5% class V. 60.53%, 52.63%, and 42.11% had consumed C3, C4, and C3/C4 respectively. At the time of presentation, urinalysis did not differ between the groups. In the C3/C4 consumed group, the amount of patients with leukopenia was higher compared to the C3 consumed group (leukopenia: OR 8.12 (IC 95% 1.7 - 37.1) p 0.006) but not with the C4 consumed group. In the C3 consumed group the amount of patients with anemia was higher compared to C3/C4 consumed group (anemia: OR 8.20, (IC 95% 1.98 - 33.8) p 0.003). Creatinine levels did not differ at the time of presentation or during hospitalization. Regarding death and the initiation of renal replacement therapy (RRT), there were no differences.
In the present study, no relationship was found between complement and renal involvement, however individuals with consumed C3/C4 presented greater hematological impairment regarding leukopenia while individuals with consumed C3 presented greater hematological impairment regarding anemia. Phenotyping studies are necessary to elucidate the role of complement in lupus nephritis. Further studies incorporating new analytical techniques such as machine learning are needed to establish different presentation patterns in Latin America to compare them with other continents.