Bacterial infection in patients with juvenile systemic lupus erythematosus and fever.

Background: Juvenile Systemic Lupus Erythematosus (JSLE) is a chronic, systemic autoimmune disease characterized by an increased susceptibility to infections. Fever in these patients can result from infection, heightened lupus activity, or a combination of both. Various clinical factors and biomarkers have been proposed to differentiate between infection and disease activity, but the results remain inconclusive. The Systemic Lupus Erythematosus Disease Activity Index-2000 (SLEDAI-2 k) is used to assess lupus activity in the presence or absence of infection. This study aimed to identify factors associated with bacterial infections in JSLE patients presenting with fever.

Methods: A case-control study, approved by the institutional ethics committee, was conducted.

Results: Bacterial infection was identified in 17% of 116 patients. Factors evaluated included immunomodulator use, high-dose steroids, renal replacement therapy, erythrocyte sedimentation rate (ESR) > 20, C-reactive protein (CRP) > 60 and > 90 mg/L, ferritin > 500 ng/mL, neutrophil-to-lymphocyte ratio (NLR) > 6, platelet-to-lymphocyte ratio (PLR) > 133, procalcitonin (PCT) > 0.9 ng/mL, lymphocyte-to-C4 ratio (LC4R) > 66.7, and ESR/CRP ratio < 2. In the adjusted model, PCT > 0.9 ng/mL retained significance with p < 0.01. Nagelkerke's R² was 0.65, and the Hosmer-Lemeshow test indicated good internal validity.

Conclusions: Bacterial infection was detected in 17% of JSLE patients with fever. Procalcitonin > 0.9 ng/mL is a critical marker for identifying bacterial infection. NLR, PLR, ESR/CRP ratio, LC4R, and ferritin require further investigation to establish definitive cut-off values for differentiating bacterial infections from other infections or disease activity. Individual patient evaluation remains the recommended approach for diagnosis.