BILAG-2004 Activity Calculator
Select a grade (A-E) for each domain to estimate a weighted total score and activity summary.
Educational tool only. Clinical decisions should be made by qualified healthcare professionals.
What is the BILAG score?
The BILAG (British Isles Lupus Assessment Group) index is a structured method used to assess disease activity in systemic lupus erythematosus (SLE). Rather than producing a single number only, it grades activity by organ system, which helps clinicians identify where active disease is occurring and how severe it is.
In routine practice and research, BILAG domain grades are often converted into weighted numeric values for easier comparison over time. This page provides a simple, transparent calculator for that purpose.
How this bilag calculator works
Each of the nine BILAG-2004 domains is graded from A to E:
- A = severe/high activity
- B = moderate activity
- C = mild stable activity
- D = prior activity, currently inactive
- E = no current or previous activity
For weighted scoring in this calculator, grades are mapped as follows:
- A = 12 points
- B = 8 points
- C = 1 point
- D = 0 points
- E = 0 points
Step-by-step guide
1) Enter domain grades
Choose one grade for each domain based on the most recent clinical assessment: constitutional, mucocutaneous, neuropsychiatric, musculoskeletal, cardiorespiratory, gastrointestinal, ophthalmic, renal, and hematological.
2) Calculate the weighted total
Click Calculate BILAG Score. The tool sums weighted points and reports the number of A, B, C, D, and E grades.
3) Review the activity summary
The interpretation emphasizes active disease burden:
- Any A grade suggests high-priority active disease.
- Multiple B grades suggest significant multi-domain activity.
- C-only patterns usually indicate low but persistent activity.
- D/E dominant patterns suggest inactive disease at present.
Why domain-level scoring matters
A single total can hide important differences. Two patients may have similar point totals but very different organ involvement. Domain-level tracking makes trends visible and supports more individualized care planning.
Practical tips for clinicians and trainees
- Use consistent definitions between visits to improve reliability.
- Record rationale for each domain grade in chart notes.
- Compare BILAG trends with laboratory data and patient-reported symptoms.
- Do not rely on score conversion alone for treatment escalation decisions.
Limitations and important disclaimer
This calculator is a convenience tool for education and quick estimation. It does not replace full BILAG scoring protocols, formal training materials, institutional guidance, or clinical judgment. If you are a patient, please discuss your results with your rheumatology team.
Frequently asked questions
Is this an official diagnostic tool?
No. It is an informational calculator designed to mirror common weighted conversion methods.
Can I use this for longitudinal follow-up?
Yes, as a quick tracking aid. For research or formal audits, use validated workflows and complete source documentation.
Why do D and E both score zero?
Both represent no current active disease requiring treatment escalation, though D indicates prior activity while E indicates none historically in that domain.