Systemic lupus erythematosus (SLE) is a chronic, systemic autoimmune disease characterized by the presence of autoantibodies caused by immune system dysregulation. Its prevalence ranges from 3.2 to 300 cases per 100,000 people, with an incidence of 1.4 to 8.7 per 100,000 people [1]. SLE exhibits extensive phenotypic variability, with juvenile-onset SLE (JSLE) being the most common, accounting for 55.7% of cases. JSLE typically manifests between the ages of 7 and 13 [2] and is associated with a higher susceptibility to infections, increased disease activity, greater tissue and organ damage [3], and the need for more intensive immunosuppressive therapy [4]. The disease alternates between potentially life-threatening periods of immune activity and phases of remission [5,6,7].

In JSLE, infections contribute to morbidity and mortality in 44% of cases and increase healthcare costs by 30% due to prolonged hospitalizations and admissions to pediatric intensive care units. Infections can be bacterial, viral, or fungal in nature [8,9,10]. Approximately 50% of adults with SLE experience severe infectious episodes requiring extended hospitalization, and early identification of infected patients significantly improves outcomes [11]. Fever is a common symptom of both infection and heightened lupus activity, and these conditions often coexist. Fever is reported in 36–96% of adults with SLE, with 60% of cases attributed to disease activity, 23% to infection, and 12% to both conditions [12, 13].

Several clinical features and biomarkers have been investigated to assist clinicians in differentiating between disease activity and infection in SLE patients with fever. Evidence regarding the utility of biomarkers such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), neutrophil-to-lymphocyte ratio (NLR), ferritin, and procalcitonin (PCT) remains inconclusive [14,15,16,17,18,19,20]. Ju-Yang et al. (2019) identified serositis, hematologic involvement, and high-dose glucocorticoids (> 7.5 mg/day of prednisolone) as factors associated with severe infections, such as those requiring Intensive Care Unit (ICU) hospitalization or intravenous antibiotic use [21].

Zhai et al. (2021) reported a scoring system for identifying bacterial infections in adults with SLE, achieving an area under the curve (AUC) of 0.842 and a 95% confidence interval (CI) of 0.794–0.891. Variables such as white blood cell count, neutrophil count, ESR, CRP, PCT, interleukin-6, interleukin-10, interferon-gamma, and tumor necrosis factor-alpha were significantly elevated in patients with bacterial infections [22].

In pediatrics, Luo et al. reported that the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI), fever, CRP, PCT, lymphocyte percentage, NLR, hemoglobin, and the SLE Disease Activity Index 2000 (SLEDAI-2 K) are predictive of infection, with an area under the curve (AUC) of 0.7886, sensitivity of 63.5%, and specificity of 89.2%. The authors recommend individualized clinical analysis for decision-making [23].

Sari et al. identified urinary tract infections (41%), skin and soft tissue infections (20.5%), and pneumonia (20.5%) as the most common infections, with methylprednisolone pulse therapy being a predictor of infection [24].

Disease activity indices, such as SLEDAI, are designed to classify disease activity regardless of the triggering cause [25,26,27]. Biomarkers like NLR, ESR/CRP ratio, platelet-to-lymphocyte ratio (PLR), and lymphocyte/C4 index (L/C4) have been studied in adult Colombian populations to differentiate infection from disease activity. The optimal cutoff values for infection detection were NLR > 6, ESR/CRP ratio < 2, PLR > 132, and L/C4 index > 66.7 [28].

The objective of this study is to identify factors associated with bacterial infections in JSLE patients with fever.

The study protocol was approved by the Pediatric Research Group (GRINPED) under record 072 on August 12, 2023; the Ethics and Bioethics Research Committee of Fundación Clínica Infantil Club Noel under registration 268 on October 20, 2023; and the Ethics Committee of Universidad Libre Seccional Cali, Colombia (Resolution CEB-10–2024, dated March 28, 2024), in accordance with the Declaration of Helsinki of the World Medical Association.