DARES Formula in Rheumatoid Arthritis Disease Activity Assessment
The DARES formula is not a recognized or standardized assessment tool in medical practice, particularly for rheumatoid arthritis disease activity measurement. Instead, clinicians should use validated measures like SDAI (Simplified Disease Activity Index) and CDAI (Clinical Disease Activity Index) which are recommended by the American College of Rheumatology for assessing rheumatoid arthritis disease activity 1.
Validated Disease Activity Measures for Rheumatoid Arthritis
SDAI (Simplified Disease Activity Index)
- Calculated as the sum of five components: 28-joint swollen joint count, 28-joint tender joint count, provider global assessment of disease activity, patient global assessment of disease activity, and C-reactive protein measurement 1
- Uses a scale of 0-86 with disease activity categories: Remission (≤3.3), Low (>3.3 to ≤11.0), Moderate (>11.0 to ≤26), and High/severe (>26) 1
- Includes C-reactive protein as an objective inflammatory marker but requires waiting for laboratory results 1
CDAI (Clinical Disease Activity Index)
- Calculated as the sum of four components: 28-joint swollen joint count, 28-joint tender joint count, provider global assessment of disease activity, and patient global assessment of disease activity 1
- Uses a scale of 0-76 with disease activity categories: Remission (≤2.8), Low (>2.8 to 10.0), Moderate (>10.0 to 22.0), and High/severe (>22.0) 1
- Has the advantage of not requiring laboratory tests, making it immediately calculable at the point of care 1, 2
DAS28 (Disease Activity Score with 28-joint count)
- Uses a more complex calculation requiring differential weighting of individual indices 2
- Weighs tender joint count more heavily than swollen joint count 2
- Generally uses ESR, although DAS28-CRP is also available 2
- Less conservative remission criteria compared to SDAI and CDAI 1
Clinical Application and Advantages
- The American College of Rheumatology recommends using validated measures like SDAI and CDAI for assessing disease activity in clinical practice 1, 2
- CDAI has the advantage of providing real-time results at the point of care without needing laboratory tests 2
- SDAI and CDAI use simple arithmetic addition, making them easier to calculate in clinical practice compared to DAS28 which requires a more complex formula 2, 1
- Treating to a target level (such as DAS28 ≤2.4) has been shown to improve rheumatoid arthritis outcomes 2
Important Considerations
- Proper training in joint count assessment is essential for accurate calculation of disease activity measures 1
- The inclusion of acute-phase reactants (like ESR or CRP) in measures like DAS28 and SDAI introduces additional variables and complexity 2
- ESR contributes approximately 15% of the information in the DAS28-ESR, which may lead to underestimation of remission in high ESR states with few active joints 2
- Newer biologic agents targeting specific inflammatory cytokines may disproportionately affect acute-phase reactants, potentially deflating composite scores 2
Practical Implementation
- Disease activity measures should be used as part of a comprehensive approach to RA management that includes assessment of function and structural damage 1
- While the PsARC (Psoriatic Arthritis Response Criteria) was developed specifically for psoriatic arthritis, it is not applicable to rheumatoid arthritis assessment 2
- Logistical barriers have delayed widespread adoption of complex measures in smaller practice settings 2
- Regular monitoring using consistent disease activity measures helps guide treatment decisions and assess response to therapy 2