Simplified Disease Activity Index for RA (SDAI)

Assess disease activity in rheumatoid arthritis.

The global unit selector only affects unanswered questions
2.Swollen Joint Count?
3.Tender Joint Count?
4.Patient Global Assessment?
5.Evaluator Global Assessment?
Created by

1. CRP?

Created by
0/5 completed

About this Calculator

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.

A simplified disease activity index for rheumatoid arthritis for use in clinical practice.

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

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