Background Despite the advances in the management of systemic lupus erythematosus (SLE), mortality rate among patients with SLE significantly remained higher compared to non-SLE over time. Serious infections (SIs) were likely one of the leading causes of death in SLE patients over the last few years. The aim of this study was to evaluate the incidence and identify predictive factors of SIs over time in Thai patients with SLE.

Methods We evaluated SLE patients followed up at Lupus Clinic of Royal Thai Army (LUCRA) between March 2018 and September 2022. SIs were defined as ones that received intravenous antibiotic, required hospitalization, or led to death. Multivariable regression analyses were performed to identify factor predicting of SIs.

Results Of the 237 patients included, 22 (9.28%) had SIs at least once during the follow-up time. The median (interquartile range) onset of SIs after enrollment was 29.75 (4.25–34) months. The incidence rate of SIs was 2.4 events per 100 person-years. Pneumonia caused by gram-negative pathogens was the most common cause of SIs. Multivariable analysis revealed that predictive factors of SIs were prednisolone intake (hazard ratio (HR): 1.06; 95% confidence interval (CI): 1.01–1.11; p=0.15), doses of prednisone >7.5 mg/day (HR: 3.08; 95%CI: 1.34–10.77; p=0.012), and > 10 mg/day (HR: 3.61; 95%CI: 1.21–10.80; p=0.021). In addition, use of mycophenolic acid was independent factor associated with increased risk of SIs when adjusting prednisolone > 5 mg/day (HR: 2.95; 95% CI: 1.01–8.58; p=0.047). The other factors predicted SIs included hypertension (HR: 3.45; 95% CI: 1.28–9.34; p=0.015), and damage accrual (HR: 3.34; 95% CI: 1.92–5.83; p< 0.012).

Conclusions Prednisone had a dose-dependent effect on increasing risk of SIs. Moreover, use of mycophenolic acid, underlying hypertension, and damage accrual influenced SIs in SLE patients over time.