Enter the Tender Joint Count, Swollen Joint Count, Patient’s Global Assessment, and Evaluator’s Global Assessment into the calculator to determine the Clinical Disease Activity Index.

CDAI Calculator

Enter all fields to calculate CDAI.

Medical disclaimer: This calculator is for informational/educational purposes only and does not provide medical advice or a diagnosis. CDAI scoring and interpretation (including joint counts) should be performed and reviewed by a qualified healthcare professional (such as a rheumatologist). Do not start/stop/change medications based on this result; seek medical care promptly for severe or worsening symptoms.

CDAI (Clinical Disease Activity Index) Formula

The following formula is used to calculate the Clinical Disease Activity Index (CDAI).

CDAI = TJC28 + SJC28 + PtGA + PrGA

Variables:

  • SJC28 = swollen joint count (28 joints; range 0–28)
  • TJC28 = tender joint count (28 joints; range 0–28)
  • PrGA = Provider/Physician Global Assessment of disease activity (0–10 scale)
  • PtGA = Patient’s Global Assessment of disease activity (0–10 scale)

To calculate the Clinical Disease Activity Index, add the Tender Joint Count (TJC28), Swollen Joint Count (SJC28), Patient’s Global Assessment (PtGA, 0–10), and Provider/Physician Global Assessment (PrGA, 0–10). CDAI is an unweighted sum (no multipliers are used).

What is a CDAI (Clinical Disease Activity Index)?

The Clinical Disease Activity Index (CDAI) is a tool used by healthcare professionals to measure disease activity in patients with rheumatoid arthritis. It assesses the number of swollen and tender joints, along with the patient’s and physician’s global assessment of disease activity. The CDAI provides a numerical score that helps in tracking the disease progression and the effectiveness of treatment over time. It does not require laboratory tests, making it a practical tool for clinical settings.

How to Calculate CDAI (Clinical Disease Activity Index)?

The following steps outline how to calculate the Clinical Disease Activity Index (CDAI).

  1. First, determine the value of the Tender Joint Count (TJC28).
  2. Next, determine the value of the Swollen Joint Count (SJC28).
  3. Next, determine the value of the Patient Global Assessment of disease activity (PtGA) on a scale of 0-10.
  4. Next, determine the value of the Provider/Physician Global Assessment of disease activity (PrGA) on a scale of 0-10.
  5. Using the formula CDAI = TJC28 + SJC28 + PtGA + PrGA, calculate the Clinical Disease Activity Index (CDAI).
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Tender Joint Count (TJC28) = 5

Swollen Joint Count (SJC28) = 3

Patient Global Assessment (PtGA) = 7

Provider/Physician Global Assessment (PrGA) = 6

CDAI = 5 + 3 + 7 + 6 = 21

References

For official definitions, intended use, and interpretation thresholds for CDAI (including how joint counts and global assessments are performed), consult reputable clinical resources such as American College of Rheumatology (ACR) materials, EULAR resources, and peer-reviewed rheumatology publications.