Intercurrent infection as a risk factor for disease flares in patients with systemic lupus erythematosus

To determine whether intercurrent infections are a risk factor for subsequent disease flares in systemic lupus erythematosus (SLE).

Demographic and clinical characteristics of 203 patients with SLE participating in the Amsterdam SLE cohort were collected at baseline and during follow-up. Collection of data on infections and SLE flares was registry-based and infections and flares were categorised as minor or major, based on predefined criteria. Proportional hazard models with recurrent events and time-varying covariates were used to estimate the HR of SLE flares.

The incidence rates of major and minor infections were 5.3 per 100 patient years and 63.9 per 100 patient years, respectively. The incidence rates of flares were 3.6 and 15.1 per 100 patient years for major flares and minor flares, respectively.In the proportional hazard model, intercurrent infections (major and minor combined) were associated with the occurrence of SLE flares (major and minor combined; HR 1.9, 95% CI: 1.3 to 2.9). The hazard ratio for a major SLE flare following a major infection was 7.4 (95% CI: 2.2 to 24.6). Major infections were not associated with the occurrence of minor flares.

The results of the present study show that intercurrent infections are associated with subsequent SLE flares, which supports the hypothesis that infections may trigger SLE flares.