CDAI Calculator for RA – Clinical Disease Activity Index for Rheumatoid Arthritis

A simple tool for assessing Rheumatoid Arthritis disease activity.

CDAI Calculator

Your CDAI Score: 0

0 – 2.8 : Low Disease Activity

2.81 – 10 : Moderate Disease Activity

10.01 – 22 : High Disease Activity

> 22 : Very High Disease Activity

About CDAI Calculator

CDAI, Clinical Disease Activity Index, is a simplified metric used in rheumatology. It assesses the disease activity in patients with Rheumatoid Arthritis. It is simpler than its predecessor, the SDAI. CDAI score doesn't necessitate the measurement of an acute phase reactant. Instead, it harnesses the power of clinical assessments identical to the SDAI.

The formula for computing in CDAI Calculator is:

\text{CDAI} = \text{SJC} + \text{TJC} + \text{PGA} + \text{EGA}


  • SJC: Swollen Joint Count
  • TJC: Tender Joint Count
  • PGA: Patient Global Assessment of Disease Activity
  • EGA: Evaluator Global Assessment of Disease Activity

How to Use CDAI Calculator

Let's see how to quickly determine the CDAI score.

1. Inputting the Swollen Joint Count (SJC): Begin by entering the count of swollen joints (Between 0-28). This is the primary symptom of active RA.

2. Entering the Tender Joint Count (TJC): Next, input the tender joint count (Between 0-28). The tenderness might signify inflammation or damage in the joint.

3. Incorporating the Patient Global Assessment (PGA): Here, the patient's perception of their disease activity is taken into account (Between 0-10). This is a subjective measurement to understand the patient's condition.

4. Adding the Evaluator Global Assessment (EGA): The final input comes from a medical evaluator's standpoint (Between 0-10). It's an assessment from a clinical perspective, requires medical knowledge.

Upon entering all these values, the calculator provides a CDAI score, which can then be interpreted to understand the disease's current activity level.


  • How is CDAI different from SDAI?

    CDAI simplifies the SDAI approach by eliminating the need for measuring an acute phase reactant. It is only based on clinical assessments.
    (Want to calculate SDAI? Go here -> SDAI Calculator)

  • What do the CDAI score ranges indicate?

    The scores are interpreted as:
    ≤2.8: Remission
    2.8 and ≤10: Low Disease Activity
    10 and ≤22: Moderate Disease Activity
    >22: High Disease Activity

CDAI Score in Clinical Decision-Making

Clinical decision-making in the domain of rheumatology has witnessed revolutionary changes over the past few decades. CDAI correlates well with other disease activity scores and response criteria. So it provides an efficient, immediate metric to base treatment decisions.

CDAI simply and fastly predicts joint damage progression and functional impairment. This helps that patients get effective interventions, in time. More about rheumatoid arthritis is here.

Limitations of CDAI Score

While CDAI is powerful tool, it has its embedded limitations. The most evident limitation is its reliance on clinical assessments without the backup of acute phase reactant measurements. This means that while it provides a rapid metric, there may be instances where the disease's systemic effects aren't completely captured. Also, the subjectivity of both PGA and EGA might lead to variability in scores. Nevertheless, when used judiciously and in conjunction with other assessments, the CDAI remains a reliable tool. If you need more details in RA and the measurement tools, go to this comprehensive guide.


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 Research & Therapy 2005, 7 (4): R796-806

Aletaha D, Smolen J.
The SDAI and the CDAI: a review of their usefulness and validity in rheumatoid arthritis.
Clinical and Experimental Rheumatology 2005, 23 (5 Suppl 39): S100-8

The Clinical Disease Activity Index for RA (CDAI) calculator is created by QxMD.