Simplified Disease Activity Index for RA (SDAI)

Assess disease activity in rheumatoid arthritis.


The Simplified Disease Activity Index for Rheumatoid Arthritis (SDAI) is a scoring system that has been validated in both research and clinical settings. It has been shown to have the highest sensitivity and specificity for predicting a physicians' decisions to change DMARD therapy when compared to other scores.

In an observational study, a score ≥15 had the best combination of sensitivity (90%) and specificity (86%) when compared to a clinical decision to change DMARDs because of inadequate control of disease. Remission is defined as an SDAI of <3.3, low disease activity as ≤11, moderate disease activity as ≤26 and high disease activity as >26.

Response to therapy is considered moderate if SDAI decreases by ≥7 and major if decreases by ≥17

SDAI is calculated as follows:



  • SJC = Swollen Joint Count
  • TJC = Tender Joint Count
  • PGA = Patient Global Assessment of Disease Activity
  • EGA = Evaluator Global Assessment of Disease Activity
  • CRP = CRP in mg/dL


Smolen JS, Breedveld FC, Schiff MH, et. al.

Rheumatology, Volume 42, Issue 2, February 2003, Pages 244–257

The Simplified Disease Activity Index for RA (SDAI) calculator is created by QxMD.

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1. CRP?

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