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CDAI (Clinical Disease Activity Index)

Laboratory-free disease activity in rheumatoid arthritis

Sources last checked: 2026-10-13

CDAI (Clinical Disease Activity Index)

Laboratory-free disease activity in rheumatoid arthritis

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Both global assessments are entered on a 0–10 scale (cm VAS or NRS). Fibromyalgia or osteoarthritis can inflate tender counts and the patient global.

Source: 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-R806.Open

Interpretation

≤ 2.8 — remissionACR/EULAR 2011 index-based remission definition for clinical practice.
> 2.8 to 10 — low disease activity
> 10 to 22 — moderate disease activity
> 22 — high disease activity

What is the CDAI (Clinical Disease Activity Index)?

The Clinical Disease Activity Index (CDAI) is the simple sum of tender and swollen joint counts (28 joints) and patient and evaluator global assessments on 0–10 scales. It was validated by Aletaha, Smolen and colleagues in Vienna in 2005 as a laboratory-free version of the SDAI. Because no blood test is needed, it can be calculated during the visit.

When to use it

  • At every rheumatoid arthritis visit when the result is needed during the visit itself
  • When CRP/ESR are unavailable or confounded (e.g. on IL-6 blockade or JAK inhibitors)
  • To define remission for clinical practice (CDAI ≤ 2.8)

When not to use it

  • In other inflammatory arthritides without validation
  • When pain from fibromyalgia or osteoarthritis dominates the joint count — interpret with care

How it is calculated

CDAI = TJC28 + SJC28 + patient global (0–10) + evaluator global (0–10) Range 0–76.

Clinical pearls and limitations

  • Both global assessments are entered on a 0–10 scale (cm VAS or NRS). Fibromyalgia or osteoarthritis can inflate tender counts and the patient global.
  • Global assessments are on 0–10 (not 0–100 mm) — the commonest entry error.
  • CDAI ≤ 2.8 is one of the ACR/EULAR 2011 index-based remission definitions and is stricter than DAS28 < 2.6.
  • A change of about 12 points is considered clinically important in high disease activity (ACR 2019 summary).

Frequently asked questions

What CDAI score is remission?

2.8 or less. Low disease activity is > 2.8 to 10, moderate > 10 to 22, high > 22.

What is the difference between CDAI and SDAI?

The SDAI adds CRP in mg/dL; the CDAI omits it so it can be calculated without a blood test.

What is the maximum CDAI?

76 (28 + 28 + 10 + 10).

Evidence and guidelines

  1. Primary source: 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-R806.
  2. England BR et al. 2019 Update of the ACR recommended RA disease activity measures. Arthritis Care Res 2019;71(12):1540-1555 (CDAI and SDAI category cut-offs).
  3. Felson DT et al. ACR/EULAR provisional definition of remission in rheumatoid arthritis for clinical trials. Arthritis Rheum 2011;63(3):573-586.
  4. Smolen JS et al. Treating rheumatoid arthritis to target: 2014 update. Ann Rheum Dis 2016;75(1):3-15.

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