DAS28 Calculator
Calculate Disease Activity Score for Rheumatoid Arthritis using the 28-joint count assessment
Patient Assessment
Results
Interpretation Scale
Clinical Significance
- • Change > 1.2 = clinically important improvement
- • Change > 0.6 = meaningful response
- • Target: DAS28 < 3.2 or remission
- • Assess every 1-3 months during active treatment
Understanding DAS28 Score
The Disease Activity Score 28 (DAS28) is a validated composite measure used to assess disease activity in rheumatoid arthritis (RA). It combines objective joint examination findings with inflammatory markers and patient-reported outcomes to provide a comprehensive assessment of RA disease activity.
Components of DAS28
- Tender Joint Count (TJC28): Number of tender joints out of 28 assessed joints
- Swollen Joint Count (SJC28): Number of swollen joints out of 28 assessed joints
- ESR or CRP: Erythrocyte sedimentation rate (mm/hr) or C-reactive protein (mg/L)
- Patient Global Assessment: Visual analog scale (0-100 mm) rating overall disease activity
Formula Calculation
DAS28-ESR:
0.56 × √(TJC28) + 0.28 × √(SJC28) + 0.70 × ln(ESR) + 0.014 × VAS
DAS28-CRP:
0.56 × √(TJC28) + 0.28 × √(SJC28) + 0.36 × ln(CRP+1) + 0.014 × VAS + 0.96
Clinical Application
The DAS28 score guides treatment decisions in rheumatoid arthritis management:
- Treatment Targets: Aim for remission (DAS28 < 2.6) or low disease activity (< 3.2)
- Treatment Escalation: Consider intensifying therapy if DAS28 > 3.2 despite treatment
- Monitoring Frequency: Assess monthly to quarterly based on disease activity and treatment changes
- Response Assessment: Improvement of > 1.2 points indicates good response to therapy
Joint Assessment Guide
The 28 joints assessed include:
- Shoulders (2)
- Elbows (2)
- Wrists (2)
- Metacarpophalangeal joints (10)
- Proximal interphalangeal joints (10)
- Knees (2)
Disease Activity Categories
| DAS28 Range | Category | Clinical Meaning | Treatment Approach |
|---|---|---|---|
| < 2.6 | Remission | Minimal or no disease activity | Continue therapy, monitor regularly |
| 2.6 - 3.2 | Low Activity | Well-controlled disease | Maintain treatment, consider tapering |
| 3.2 - 5.1 | Moderate Activity | Suboptimal control | Consider treatment optimization |
| > 5.1 | High Activity | Severe, uncontrolled disease | Urgent treatment escalation needed |
Frequently Asked Questions
What is the difference between DAS28-ESR and DAS28-CRP?
Both versions assess the same disease activity but use different inflammatory markers. DAS28-ESR uses erythrocyte sedimentation rate, while DAS28-CRP uses C-reactive protein. CRP is often preferred because it's more specific for inflammation and has less variability. The formulas differ slightly with a constant added to DAS28-CRP to align the scores.
How often should DAS28 be measured?
DAS28 should be assessed every 1-3 months in patients with active disease or when treatment is being adjusted. Once remission or low disease activity is achieved and stable, monitoring can be extended to every 3-6 months.
What constitutes a meaningful change in DAS28?
A decrease of more than 1.2 points is considered a clinically important improvement and indicates a good response to treatment. A change of 0.6-1.2 points represents moderate improvement. Changes less than 0.6 points are generally not considered clinically meaningful.
Can DAS28 be used for other forms of arthritis?
DAS28 was specifically developed and validated for rheumatoid arthritis. While it may be used to track inflammation in other inflammatory arthritides, it has not been validated for these conditions. Other scoring systems may be more appropriate for conditions like psoriatic arthritis or ankylosing spondylitis.
What is the target DAS28 score in treat-to-target strategies?
Modern RA management follows a treat-to-target approach, aiming for remission (DAS28 < 2.6) as the primary goal. If remission cannot be achieved, low disease activity (DAS28 < 3.2) is an acceptable alternative target. Treatment should be adjusted if these targets are not met within 3-6 months.
How does patient global assessment affect the DAS28 score?
The patient global assessment (PGA) on a 0-100 mm visual analog scale contributes to the overall DAS28 score, making it a patient-centered measure. While it has less weight than joint counts, it captures important aspects of disease impact that may not be reflected in objective measures alone. High PGA despite low joint counts may indicate fibromyalgia overlap or other factors affecting quality of life.
Are there limitations to using DAS28?
DAS28 has some limitations: it doesn't include feet joints which may be affected in RA, it can be influenced by fibromyalgia or obesity, and the patient global assessment may vary based on factors unrelated to RA activity. Despite these limitations, it remains one of the most widely used and validated measures of RA disease activity.
What are EULAR response criteria based on DAS28?
EULAR (European League Against Rheumatism) defines treatment response based on both the current DAS28 and the amount of improvement: Good response requires improvement > 1.2 and current DAS28 ≤ 3.2; Moderate response is improvement 0.6-1.2 with DAS28 ≤ 5.1, or improvement > 1.2 with DAS28 > 3.2; No response is improvement < 0.6 or improvement 0.6-1.2 with DAS28 > 5.1.
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