A Disease Activity Score (DAS) indicates the severity of rheumatoid arthritis disease activity at a given moment in time. It is calculated based on several different factors, including lab results, patient feedback, and joint swelling and tenderness.
A traditional DAS score requires examining 44 specific joints and is sometimes referred to as DAS44. The 44 joints include:
- Sternoclavicular joints (2), which connect the collarbone and the breastbone
- Acromioclavicular joints (2), which connect the acromion to the clavicle
- Shoulders (2)
- Elbows (2)
- Wrists (2)
- Large knuckles (10) also called the metacarpophalangeal (MCP) joints
- Middle knuckles (10), also called proximal interphalangeal (PIP) joints
- Knee (2)
- Ankle (2)
- Large knuckles of the toes (10), also called the metatarsophalangeal (MTP) joints
DAS28 is a simplified version of DAS44 that evaluates just 28 joints. It does not include the ankles or joints in the feet. Physicians and researchers tend to use the DAS28 more often than the DAS44.
The DAS28 score is arrived at using:
- The number of swollen joints (out of the 28),
- The number of tender joints (out of the 28),
- The C reactive protein (CRP) or erythrocyte sedimentation rate (ESR) lab test results
- Answers to a patient health assessment questionnaire
A mathematical formula is used to calculate the overall score. DAS28 can range from 0 to 9.4.
Generally, a DAS28 score of1:
- More than 5.1 indicates high disease activity
- Between 3.2 and 5.1 indicates moderate disease activity
- Between 2.6 and less than 3.2 indicates low disease activity
- Lower than 2.6 indicates disease remission
DAS and DAS28 may be used to measure whether a treatment plan is working.