DAS28 Calculator — Disease Activity Score 28 for Rheumatoid Arthritis
The DAS28 (Disease Activity Score 28) is the most widely used composite index for assessing disease activity in rheumatoid arthritis (RA). It combines tender and swollen joint counts (28-joint assessment), acute phase reactant (ESR or CRP), and patient global assessment into a single score for monitoring treatment response and guiding therapy decisions.
About
The DAS28 was developed by Prevoo et al. in 1995 and validated as a reliable measure of RA disease activity. The 28-joint count includes shoulders, elbows, wrists, MCPs, PIPs, and knees (excluding hips, ankles, and feet). The composite score incorporates four components: tender joint count (TJC28), swollen joint count (SJC28), acute phase reactant (ESR by Westergren method or CRP), and patient global assessment of disease activity on a 100 mm VAS.
Formula
DAS28-ESR = 0.56 × √(TJC28) + 0.28 × √(SJC28) + 0.70 × ln(ESR) + 0.014 × PGA DAS28-CRP = 0.56 × √(TJC28) + 0.28 × √(SJC28) + 0.36 × ln(CRP+1) + 0.014 × PGA + 0.96
The DAS28 is calculated using four components. Tender Joint Count (TJC28): count of painful joints on palpation from the 28-joint assessment (0-28). Swollen Joint Count (SJC28): count of swollen joints from the same 28-joint assessment (0-28). Acute Phase Reactant: either ESR (erythrocyte sedimentation rate in mm/h) using the DAS28-ESR formula, or CRP (C-reactive protein in mg/L) using the DAS28-CRP formula. Patient Global Assessment (PGA): patient-reported overall disease activity on a 0-100 mm visual analogue scale. For DAS28-ESR: 0.56√(TJC) + 0.28√(SJC) + 0.70 ln(ESR) + 0.014(PGA). For DAS28-CRP: 0.56√(TJC) + 0.28√(SJC) + 0.36 ln(CRP+1) + 0.014(PGA) + 0.96. The DAS28-CRP formula includes a correction factor (+0.96) to improve concordance with DAS28-ESR. Interpretation: <2.6 remission, 2.6-3.2 low disease activity, >3.2-5.1 moderate disease activity, >5.1 high disease activity.
Score Interpretation
The DAS28 is the most validated and widely used disease activity measure in rheumatoid arthritis clinical practice and trials. It is endorsed by the American College of Rheumatology (ACR), European Alliance of Associations for Rheumatology (EULAR), and treat-to-target recommendations. The DAS28 has been validated against radiographic progression, functional status (HAQ-DI), and patient-reported outcomes. A change of >0.6 is considered clinically meaningful, and >1.2 represents a major response. The treat-to-target strategy recommends targeting DAS28 <2.6 (remission) or at least <3.2 (low disease activity).
Remission — 0–2.59
DAS28 <2.6. Disease activity is well-controlled. Continue current therapy.
Management: Consider tapering DMARD if remission sustained >6 months. Monitor every 3-6 months. Maintain physical therapy.
Low Disease Activity — 2.6–3.2
DAS28 2.6-3.2. Acceptable control, close to target.
Management: Continue current DMARD. Consider escalation if not at target within 3 months. Assess radiographic progression.
Moderate Disease Activity — 3.21–5.1
DAS28 3.2-5.1. Active disease requiring treatment escalation.
Management: Escalate DMARD therapy. Consider adding biologic or targeted synthetic DMARD. Refer to rheumatology specialist.
High Disease Activity — 5.11–9.4
DAS28 >5.1. Severe active disease requiring urgent intervention.
Management: Urgent rheumatology review. Initiate or escalate biologic DMARD. Consider short-term corticosteroids. Assess for systemic complications.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Adults with rheumatoid arthritis | <2.6 Remission to 9.4 High activity | <2.6 Remission, 2.6-3.2 Low, 3.2-5.1 Moderate, >5.1 High |
Dr. Mahmoud El-Sayed
Dr. Mahmoud El-Sayed is a consultant rheumatologist with expertise in inflammatory arthritis, autoimmune diseases, and clinical immunology.
View medical review board & editorial policy →Example Calculation
A 45-year-old woman with RA: TJC28 = 8, SJC28 = 6, ESR = 35 mm/h, PGA = 60/100. DAS28-ESR = 0.56×√(8) + 0.28×√(6) + 0.70×ln(35) + 0.014×60 = 0.56×2.83 + 0.28×2.45 + 0.70×3.56 + 0.84 = 1.58 + 0.69 + 2.49 + 0.84 = 5.60. High disease activity. Recommendation: Escalate DMARD, consider biologic therapy, urgent rheumatology referral.
Related Conditions
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Common Mistakes
Including hips, ankles, and feet in the 28-joint count
The DAS28 specifically uses a 28-joint count excluding hips, ankles, and feet. If these joints are involved, they should be documented separately but do not contribute to the DAS28 score.
Using ESR in mm/h and CRP in mg/dL interchangeably without unit conversion
DAS28-ESR uses ESR in mm/h (Westergren). DAS28-CRP uses CRP in mg/L. If CRP is reported in mg/dL, multiply by 10 to convert to mg/L before using the formula.
Frequently Asked Questions
What is the difference between DAS28-ESR and DAS28-CRP?
How often should DAS28 be measured?
References
- Prevoo ML, van 't Hof MA, Kuper HH, et al. Modified disease activity scores that include twenty-eight-joint counts. Development and validation in a prospective longitudinal study of patients with rheumatoid arthritis. Arthritis Rheum. 1995;38(1):44-48. PubMed
- Van der Heijde DM, van 't Hof MA, van Riel PL, et al. Development of a disease activity score based on judgment in clinical practice by rheumatologists. J Rheumatol. 1993;20(3):579-581. PubMed
- Smolen JS, Breedveld FC, Burmester GR, 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. PubMed