Introduction: Infections commonly complicate the course of systemic lupus erythematosus (SLE). Our aim is to investigate the clinical predictors of major infections in patients with SLE.
Methods: A nested case-control study design was used within the prospective Lupus-Cruces cohort. The endpoints of the study were major infections. Cases were defined as patients with a major infection. Two controls (SLE patients without major infections), matched for time of follow-up until the event and age at diagnosis, were selected for each case. Univariate analysis and logistic regression models were used for the analysis of data.
Results: Two hundred and forty-nine patients (83 cases, 166 controls) were selected. Eighty-three episodes of major infections were analyzed; E. coli, S. aureus, M. tuberculosis and S. pneumoniae being the most frequent isolates. Univariate analysis identified several variables related with infection: lung and renal involvement, at or previous to the study point; leukopenia at the study point; antiphospholipid antibody-positivity and treatment with prednisone within 3 months previous to the study point, and the dose of prednisone received. Treatment with antimalarials, on the other hand, showed a strong inverse association with major infections. Logistic regression models identified treatment with antimalarials (odds ratio (OR) = 0.06, 95% confidence interval (CI) = 0.02 to 0.18), prednisone dose (OR = 1.12, 95% CI = 1.04 to 1.19) and lung involvement (OR = 4.41, 95% CI = 1.06 to 18.36) as significant and independent predictors of major infections. No significant interactions among these three variables were found. Further adjustment for potential confounders related with antimalarial treatment did not change the results.
Conclusions: The risk of major infections in patients with SLE is mostly influenced by treatment. Prednisone treatment, even at moderate doses, increases the risk, whilst antimalarials have a protective effect.