Impact of severe infections in SLE: an observational study from the Spanish national registry.

Objective: Infections are a common complication of SLE. Our objective was to evaluate their causes and impact on the survival of patients with SLE.

Methods: Analysis of the admissions and death causes in patients diagnosed with SLE from the Spanish Hospital Discharge Database and the infection-related deaths of the Spanish population from the National Statistical Institute, between 2016 and 2018.Only infections recorded as the main diagnosis were analysed (severe or clinically relevant infection).

Results: Among 18 430 admissions in patients with SLE, disease activity was the cause of admission in 19% of all patients and infection in 15%. However, infection was the main cause of death (25%) while SLE activity was responsible for only 6% of deaths (p<0.001). Severe infection exceeded SLE as a cause of death for patients dying at ages between 40-59 (23% vs 4%, p<0.001), 60-79 (26% vs 6%, p<0.001) and older than 80 years (25% vs 6%, p<0.001). Infection was the cause of death in 8% of the Spanish population, a significantly lower rate when compared with patients with SLE (p<0.001). Compared with the general population, infections were the highest relative cause of death in patients with SLE, particularly at younger ages: 40% vs 3% for those below 20 years old (p<0.01), 33% vs 4% between 20 and 39 (p<0.001), 23% vs 5% between 40 and 59 (p<0.001), 26% vs 5% between 60 and 79 (p<0.001) and 25% vs 9% for those older than 80 years (p<0.001).

Conclusion: Our nationwide study confirms that infections are the leading cause of death in SLE in Spain, with the highest proportion occurring in young patients with lupus compared with the general population of the same age range.