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DAS28-CRP

Disease Activity Score in 28 joints with CRP — rheumatoid arthritis

Sources last checked: 2026-10-13

DAS28-CRP

Disease Activity Score in 28 joints with CRP — rheumatoid arthritis

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The DAS28 cut-offs were developed for DAS28-ESR. DAS28-CRP is not interchangeable with it — the same patient can fall into a different category, so follow-up comparisons are valid only within one version.

Source: DAS28-CRP(4) formula as published by the DAS developers (Radboud University Nijmegen, das-score.nl); derived from Prevoo ML et al. Arthritis Rheum 1995;38(1):44-48.Open

Interpretation

< 2.6 — remissionDAS28 remission threshold.
2.6 to < 3.2 — low disease activityNamed by the treat-to-target recommendations (Smolen 2016) as an acceptable target where remission is not achievable.
3.2 to ≤ 5.1 — moderate disease activityAbove the treat-to-target goal; the T2T recommendations (Smolen 2016) provide for therapy adjustment when the target is not reached.
> 5.1 — high disease activityAbove the treat-to-target goal; the T2T recommendations (Smolen 2016) provide for therapy adjustment when the target is not reached.

What is the DAS28-CRP?

DAS28-CRP is the version of the 28-joint Disease Activity Score that uses C-reactive protein (mg/L) instead of the ESR. It combines tender and swollen joint counts, CRP and the patient's global assessment. The formula is published by the DAS developers in Nijmegen and is widely used in trials and routine practice because CRP is easier to standardise than ESR.

When to use it

  • To measure rheumatoid arthritis activity when CRP is the available inflammatory marker
  • In treat-to-target follow-up, consistently with the same version each time
  • When ESR is unreliable (older age, anaemia, hypergammaglobulinaemia)

When not to use it

  • Interchangeably with DAS28-ESR during follow-up of the same patient
  • On IL-6 receptor blockade, where CRP is suppressed independently of disease activity

How it is calculated

DAS28-CRP = 0.56·√TJC28 + 0.28·√SJC28 + 0.36·ln(CRP + 1) + 0.014·GH + 0.96 CRP in mg/L; GH = patient global assessment on a 0–100 mm VAS.

Clinical pearls and limitations

  • The DAS28 cut-offs were developed for DAS28-ESR. DAS28-CRP is not interchangeable with it — the same patient can fall into a different category, so follow-up comparisons are valid only within one version.
  • CRP must be in mg/L; mg/dL × 10 = mg/L.
  • The formula adds a constant of 0.96 and uses ln(CRP + 1), so a CRP of 0 is allowed.
  • Under tocilizumab or sarilumab CRP is almost always low; DAS28-CRP then overestimates remission — the CDAI is not affected by this.

Frequently asked questions

Is DAS28-CRP the same as DAS28-ESR?

No. They use different formulas and are not interchangeable; comparisons over time are valid only within one version.

What CRP unit does DAS28-CRP use?

mg/L.

Which cut-offs apply to DAS28-CRP?

In practice the DAS28 thresholds (2.6 / 3.2 / 5.1) are applied, but they were developed for DAS28-ESR.

Evidence and guidelines

  1. Primary source: DAS28-CRP(4) formula as published by the DAS developers (Radboud University Nijmegen, das-score.nl); derived from Prevoo ML et al. Arthritis Rheum 1995;38(1):44-48.
  2. Aletaha D et al. Acute phase reactants add little to composite disease activity indices for rheumatoid arthritis. Arthritis Res Ther 2005;7(4):R796-R806 (DAS28-CRP formula as used).
  3. van Gestel AM et al. Development and validation of the European League Against Rheumatism response criteria for rheumatoid arthritis. Arthritis Rheum 1996;39(1):34-40.
  4. England BR et al. 2019 Update of the American College of Rheumatology recommended rheumatoid arthritis disease activity measures. Arthritis Care Res 2019;71(12):1540-1555.
  5. Smolen JS et al. Treating rheumatoid arthritis to target: 2014 update of the recommendations of an international task force. Ann Rheum Dis 2016;75(1):3-15.

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