Becca Scoring System for Differentiating Infection from Flare in Systemic Lupus Erythematosus
The Becca scoring system is a validated risk calculator that uses three key variables - duration of fever, anti-dsDNA antibody titers, and C-reactive protein (CRP) levels - to differentiate between infection and disease flare in febrile SLE patients with high accuracy. 1
Key Components of the Becca Scoring System
- Duration of fever: Shorter duration of fever tends to be associated with infection, while prolonged fever is more characteristic of SLE flares 1
- Anti-dsDNA antibody levels: Higher titers strongly correlate with disease activity, particularly in patients with active lupus nephritis 2, 1
- C-reactive protein (CRP): Significantly elevated CRP levels (especially >50 mg/L) suggest infection rather than disease activity 2, 1
Performance of the Becca Calculator
- The original model achieved an area under the ROC curve (AUC) of 0.92 in the development cohort and 0.79 in the validation cohort 1
- This makes it superior to using individual biomarkers alone for differentiation 3
Alternative and Enhanced Models
- Age, TLC, and CRP model: A newer model using age, total leukocyte count, and CRP demonstrated an AUC of 0.88 in development and 0.83 in validation 4
- ESR:CRP ratio plus other parameters: A model using ESR:CRP ratio >1.17, low WBC (<6.25 × 10^9/L), low neutrophils (<5.55 × 10^9/L), low CRP (<113 mg/L), and low complement levels (C3 <44.5 mg/dL, C4 <13.5 mg/dL) achieved AUC of 0.87-0.94 for distinguishing flare from infection 5
Additional Laboratory Parameters to Consider
Parameters suggesting SLE flare:
- Low complement levels (C3, C4) 2, 6, 5
- High SLEDAI-2K scores 6, 4
- Low hemoglobin 6
- Low platelet count 6
Parameters suggesting infection:
- Elevated procalcitonin (PCT) 6, 4
- High neutrophil-to-lymphocyte ratio (NLR) 6, 4
- Decreased lymphocyte percentage 6
- Elevated total leukocyte count 4, 5
- Elevated NEUT-x, NEUT-y, and NEUT-z indices 4
Clinical Implementation
When evaluating a febrile SLE patient:
- Measure the three core parameters: fever duration, anti-dsDNA antibodies, and CRP 1
- Consider additional parameters for enhanced accuracy: complement levels, CBC with differential, ESR, and procalcitonin 6, 4, 5
- Apply the Becca calculator formula to determine the probability of flare versus infection 1
- Values strongly suggesting infection warrant immediate antimicrobial therapy, while those indicating flare may require immunosuppressive treatment 3
Pitfalls and Caveats
- Some patients may have both infection and flare simultaneously (approximately 20-25% of cases), complicating diagnosis 4, 1
- CRP may be elevated in some SLE flares, particularly those with serositis 2
- Anti-dsDNA antibodies may not correlate with disease activity in all patients 2
- The calculator should be used as a supportive tool alongside clinical judgment, not as the sole determinant of treatment decisions 3, 1