DAS28-CRP Calculator
DAS28-CRP Calculator
Calculate DAS28-CRP for rheumatoid arthritis disease activity, and see the joints and biases it does not capture.
DAS28-CRP
4 inputs → activity scoreTJC 6, SJC 4, CRP 18 mg/L, patient global health 45 mm
Formula
- TJC28, SJC28
- tender and swollen joint counts out of 28: shoulders, elbows, wrists, MCPs and PIPs of both hands, and both knees — feet and ankles are not assessed
- CRP
- mg/L; +1 avoids the undefined ln(0) when CRP is undetectable
- GH
- patient global health on a 0–100 mm visual analogue scale, 0 meaning very well
- note
- DAS28-CRP runs roughly 0.3–0.5 lower than DAS28-ESR for the same disease state — the two scores are not interchangeable
Worked example
TJC 6, SJC 4, CRP 18 mg/L, patient global health 45 mm
0.56 × √6 = 1.37
0.28 × √4 = 0.56
0.36 × ln(19) = 1.06
0.014 × 45 = 0.63
1.37 + 0.56 + 1.06 + 0.63 + 0.96 = 4.58 — moderate disease activity
DAS28-CRP activity bands
| DAS28-CRP | Activity | Typical action |
|---|---|---|
| < 2.6 | Remission | Maintain current therapy |
| 2.6 – 3.19 | Low activity | Maintain, or consider a modest adjustment |
| 3.2 – 5.09 | Moderate activity | Treat-to-target — escalate therapy |
| ≥ 5.1 | High activity | Escalate therapy promptly |
What DAS28-CRP measures, and its blind spots
The 28 joints scored are the shoulders, elbows, wrists, metacarpophalangeal and proximal interphalangeal joints of both hands, and both knees. The feet and ankles are not included, which is the score’s best-known limitation — active disease confined to the forefoot, a common site in rheumatoid arthritis, can be entirely missed by a DAS28 that looks reassuring.
DAS28-CRP and DAS28-ESR are related but not interchangeable. Because CRP and ESR behave differently as inflammatory markers, DAS28-CRP tends to run roughly 0.3 to 0.5 lower than DAS28-ESR for the same underlying disease state. Applying ESR-derived remission or low-activity thresholds to a CRP-derived score therefore overstates how well controlled the disease actually is, and the two should be tracked as separate, non-interchangeable numbers over time.
The tender joint count and the patient global health score are both subjective, and together they carry a large share of the total weight in the formula. This matters most when fibromyalgia coexists with rheumatoid arthritis: widespread tenderness and a poor global health score can inflate DAS28-CRP substantially without any corresponding increase in swollen joints or in true inflammatory activity, and treating the number rather than the pattern in that setting leads to unnecessary escalation.
Frequently asked questions
Which joints are counted in DAS28?
Shoulders, elbows, wrists, metacarpophalangeal and proximal interphalangeal joints of both hands, and both knees — 28 in total. Feet and ankles are not assessed, which can miss active forefoot disease.
Can DAS28-CRP and DAS28-ESR scores be compared directly?
No. DAS28-CRP typically reads about 0.3 to 0.5 lower than DAS28-ESR for the same disease state, so using ESR-based thresholds on a CRP-derived score overstates remission.
What counts as remission on DAS28-CRP?
A score below 2.6. Low activity is 2.6 to 3.19, moderate activity 3.2 to 5.09, and high activity 5.1 or above.
Can DAS28-CRP be falsely elevated?
Yes. The tender joint count and patient global health are subjective and heavily weighted, so coexisting fibromyalgia can inflate the score without any increase in true inflammatory activity.
Related calculators
References
- Fransen J, van Riel PLCM. The Disease Activity Score and the EULAR response criteria. Clin Exp Rheumatol. 2005;23(5 Suppl 39):S93–9.
- Inoue E et al. Comparison of Disease Activity Score (DAS)28-erythrocyte sedimentation rate and DAS28-C-reactive protein threshold values. Ann Rheum Dis. 2007;66(3):407–9.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.