Multicentre retrospective cohort study assessing the incidence of serious infections in patients with lupus nephritis, compared with non-renal systemic lupus erythematosus.

Objectives: The incidence of serious infections is poorly defined in patients with lupus nephritis (LN). It is also unclear if LN influences risk of serious infections in a longitudinal analysis. The aim of this study was to determine the incidence of serious infections in patients with SLE and LN, compared with patients with SLE without LN.

Methods: A multicentre retrospective cohort study was conducted. Patients with LN identified at two tertiary centres were matched where possible with age and gender-matched patients with SLE without LN.Any infection requiring inpatient admission, occurring in the 6 months following index clinical visit, was considered serious. Cox regression was employed to investigate the association between risk of serious infection and LN status, and other relevant covariates.

Results: A total of 173 patients were included within the analysis (n=87 LN, n=86 SLE only). A total of 9.2% (n=8) of patients with LN experienced at least one serious infection within the study period, compared with 5.8% (n=5) of patients without LN, equivalent to 19.5 and 12.0 infections per 100 patient-years with and without LN, respectively. Univariable and multivariable analyses found no significant increased risk of serious infection in patients with LN versus controls (HR 1.61; 95% CI 0.53 to 4.92 and adjusted HR (aHR) 0.91; 95% CI 0.27 to 3.06, respectively). Increased prednisone dose and modified SLE comorbidity index were strongly associated with serious infection (aHR (per 5 mg) 1.21; 95% CI 1.07 to 1.37; p=0.003 and aHR 1.13; 95% CI 1.02 to 1.25; p=0.018, respectively).

Conclusions: In this cohort, adjusting for cofactors, the presence of LN alone does not appear to increase the risk of serious infections compared with patients with SLE without LN. However, increased prednisone dose at baseline visit and increasing comorbidity were independently associated with the incidence of serious infection.