Background:Infections have been associated with a higher risk of systemic lupus erythematosus (SLE) flares, but the impact of influenza infection on SLE flares has not been evaluated.Objectives:We evaluated the association between influenza infection and SLE flares resulting in hospitalization.Methods:SLE flares resulting in hospitalization and influenza cases were ascertained from the Korean national healthcare insurance database (2014-2018). We used a self-controlled case series design. We defined the risk interval as the first 7 days after the influenza index date and the control interval was defined as all other times during the observation period of each year. We estimated the incidence rates of SLE flares resulting in hospitalization during the risk interval and control interval and compared them using a Poisson regression model.Results:We identified 1,624 influenza infections among the 1,455 patients with SLE. Among those, there were 98 flares in 79 patients with SLE. The incidence ratio (IR) for flares during the risk interval as compared with the control interval was 25.75 (95% confidence interval 17.63 – 37.59). This significantly increased the IRs for flares during the risk interval in both women (IR 27.65) and men (IR 15.30), all age groups (IR 17.00 – 37.84), with and without immunosuppressive agent (IR 24.29 and 28.45, respectively), and with and without prior respiratory diseases (IR 21.86 and 26.82, respectively).Conclusion:We found significant association between influenza infection and SLE flares resulting in hospitalization. Influenza infection has to be considered as a risk factor for flares in all SLE patients regardless of age, sex, medications, and comorbidities.References:[1]Kwong, J. C. et al. Acute Myocardial Infarction after Laboratory-Confirmed Influenza Infection. N Engl J Med 2018:378;345-353.Table 1.Incidence ratios for SLE flares resulting in hospitalization after influenza infectionRisk intervalIncidence ratio95% CIDuring risk interval for 7 days / control interval25.7517.63 – 37.59Days 1-3 / control interval21.8114.71 – 32.35Days 4-7 / control interval7.563.69 – 15.47SLE, systemic lupus erythematosus; CI, confidence intervalDisclosure of Interests:None declared
Left ventricular dysfunction in asymptomatic patients with systemic lupus erythematosus