Background Anti-Sm is one of items of the 1987 American College of Rheumatology classification criteria for systemic lupus erythematosus (SLE), and it is known as a specific antibody for lupus nephritis. However, the clinical significance of anti-Sm in lupus nephritis still remains controversial, and furthermore, its potential to predict the use of immunosuppressive agents during the disease course has been little clarified.
Objectives In this study, we investigated whether anti-Sm might be a significant predictor for the progressive disease entity requiring of immunosuppressive agents in patients with biopsy-proven lupus nephritis during the follow-up period.
Methods One hundred-forty nine patients with lupus nephritis who had undergone renal biopsy were screened, and 90 patients who met the inclusion criteria were enrolled and analyzed from January 2005 to December 2014. Patients having anti-Sm, which was detected on the laboratory tests more than 6 months prior or posterior to renal biopsy, were excluded. In addition to anti-Sm, SLE disease activity index (SLEDAI), laboratory results including other autoantibodies and complements, lupus nephritis classes and treatment with immunosuppressive agents were assessed. Immunosuppressive agents included cyclophosphamide, azathioprine, mycophenolate mofetil, tacrolimus and cyclosporine, and their usages were counted when patients had received them for at least 3 months during the follow-up period.
Results The median age at the time of renal biopsy performance was 32.0 years (range 10.0–63.0) and the mean follow-up duration after renal biopsy was 35.3 months (range 1.3-117.6). Class IV (46.6%, 42 of 90) was the most frequently observed subtype of lupus nephritis, followed by class III (32.2%) and class V (26.6%). There was no association of the presence of anti-Sm with classes of lupus nephritis. During the follow up period, 73 of 90 patients (81.1%) had ever received immunosuppressive agents. Among clinical variables, the use of immunosuppressive agents was significantly associated with the presence of anti-Sm (p=0.022), and it was meaningfully correlated with age (p=0.027) and high SLEDAI (p=0.007) on univariate analysis. Multivariate analysis revealed that the use of immunosuppressive agents was associated with anti-Sm (OR 2.870, 95% confidence interval (CI), 1.033, 7.976, p=0.043), age (OR 0.958, 95% CI, 0.923-0.994, p=0.023) and SLEDAI (OR 1.185, 95% CI, 1.023, 1.373, p=0.024) (Table 1).
Conclusions In patients with biopsy-proven lupus nephritis, the presence of anti-Sm was independently associated with the use of immunosuppressive agent. Our findings indicated anti-Sm as a significant predictor for the requirement of immunosuppressive agents in lupus nephritis together with age and SLEDAI.
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Disclosure of Interest None declared