ToolsCalculators
Simple Disease Activity Index (SDAI) for Rheumatoid Arthritis
RA disease activity combining joint counts, global assessments, and CRP.
Simple Disease Activity Index (SDAI) for Rheumatoid Arthritis
Tender joint count (28-joint)
joints
Swollen joint count (28-joint)
joints
Patient global assessment of disease activity
0-10 cm visual analogue scale (0 = very well, 10 = very poor).
cm (0-10)
Evaluator (physician) global assessment of disease activity
0-10 cm visual analogue scale.
cm (0-10)
C-reactive protein
Enter as mg/dL (upper limit for scoring purposes is 10 mg/dL).
mg/dL
Complete the fields above to see the result.
When to use
- Quantifying rheumatoid arthritis disease activity and monitoring treat-to-target response when a CRP is available.
- Cross-checking CDAI when the acute-phase response is discordant with the clinical joint findings.
Formula
SDAI = tender joint count (28 joints) + swollen joint count (28 joints) + patient global assessment (0-10 cm VAS) + evaluator global assessment (0-10 cm VAS) + CRP (mg/dL, capped for scoring at 10). Range 0-86. Remission <=3.3, low activity >3.3-11, moderate activity >11-26, high activity >26.
Pearls and pitfalls
- CRP contributes only a small amount to the total score compared with the joint counts and global assessments.
- Uses the same 4 clinical components as CDAI plus CRP; CDAI can be used interchangeably when CRP is unavailable.
References
- Aletaha D, Nell VP, Stamm T, et al. Acute phase reactants add little to composite disease activity indices for rheumatoid arthritis: validation of a clinical activity score. Arthritis Res Ther. 2005;7(4):R796-806.
- Aletaha D, Ward MM, Machold KP, et al. Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states. Arthritis Rheum. 2005;52(9):2625-36.