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Discriminating Disease Flare From Infection in Febrile Patients With Systemic Lupus Erythematosus in a Safety-Net
Abhimanyu Amarnani1, Flora Liu2, Melissa Lee Wilson3
1University of Southern California Keck School of Medicine, Los Angeles, and New York University Langone Health and Bellevue Hospital Center, New York City.
ACR Open Rheumatology
|June 12, 2025
Summary
Identifying disease flare versus infection in febrile patients with systemic lupus erythematosus (SLE) is crucial. Specific laboratory markers, including ESR:CRP ratio, WBC, neutrophil, C3, and C4 levels, can effectively distinguish between flare and infection.
Area of Science:
- Rheumatology
- Clinical Immunology
- Infectious Diseases
Background:
- Distinguishing disease flare from infection is critical for managing febrile patients with Systemic Lupus Erythematosus (SLE).
- Inappropriate treatment due to misdiagnosis can lead to adverse outcomes.
Purpose of the Study:
- To identify clinical laboratory parameters differentiating disease flare from infection in febrile SLE patients.
- To develop a reliable diagnostic model for clinical use.
Main Methods:
- Retrospective review of electronic medical records from safety-net hospitals.
- Analysis of laboratory parameters including CBC, LFTs, ESR, CRP, C3, C4, lactate, procalcitonin, and ferritin within 48 hours of admission.
- Categorization of patients into disease flare, bacterial infection (culture-positive/negative), or both.
Main Results:
- An optimized multivariable logistic regression model identified key differentiating parameters.
- Elevated ESR:CRP ratio (>1.17), low WBC count (<6.25 × 10^9/L), low absolute neutrophil count (<5.55 × 10^9/L), and low CRP (<113 mg/L), C3 (<44.5 mg/dL), and C4 (<13.5 mg/dL) levels distinguished flare from infection.
- The multivariable model significantly outperformed the ESR:CRP ratio alone in discriminating flare from infection (AUC 0.87-0.94).
Conclusions:
- A combination of laboratory markers, including ESR:CRP ratio, C3, C4, WBC, neutrophil, and monocyte counts, can differentiate between SLE flare and infection.
- These findings require prospective validation for clinical implementation.
