Purpose Systematic lupus erythematosus (SLE) and lupus nephritis (LN) are associated with a higher frequency of serious infections compared to the general population which are in turn associated with adverse outcomes, morbidity and mortality. Very few studies have explored risk factors for infections in these patients and, to the best of our knowledge, there are no studies examining the association with disease activity and serious infections.
Methods We have conducted a retrospective cohort study to evaluate the prognostic significance of disease activity for serious infections in LN. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K). Serious infections were defined as those that: 1. require intravenous therapy OR 2. lead to hospitalization OR 3. have resulted in death in 30 days from diagnosis. SLE was diagnosed using the American College of Rheumatology criteria.
Results A total of 51 patients with biopsy-proven LN were followed up for 4.5±2.9 years (80% women, mean age at biopsy 38±14). Of these, 22 (43%) had at least one episode of serious infection with 4 patients having 2 episodes for an incidence of 5.7 infections per year of follow-up. Most common sites of infection were pneumonia (N=6), urinary tract infections (N=5), gastrointestinal infections (N=4) and skin infections (N=2). Five patients had sepsis with one progressing to septic shock and two patients died. Disease activity was higher at the time of biopsy compared to at the time of infection/up to one month prior to infection (15.4±6.3 vs. 11.3±5.5, p=0.001). There was no difference between either disease activity at the time of biopsy (18.0±1.0 vs. 15.5±6.5, p=0.36) or at the time of infection/preceding infection (12.0 vs. 11.25, p=0.90). SLEDAI-2K damage index at the time of biopsy was not an independent predictor of serious infection (OR 0.88 [0.72, 1.08]).
Conclusions Serious infections are common in LN with nearly half of the patients having at least one episode. While high disease activity indices are important markers of immune-mediated damage, more serious disease and adverse outcomes, SLEDAI-2K at the time of biopsy was not an independent predictor of serious infections in our cohort of patients with LN.
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