Clinical Disease Activity Index (CDAI)
What It Measures
The Clinical Disease Activity Index (CDAI) gives a single number for how active a person's rheumatoid arthritis is right now. It is used to decide whether treatment is working and whether it needs to change.
Four things are added together. A clinician counts how many of 28 specified joints are tender and how many are swollen. Then the patient rates their own disease activity from 0 to 10, and the clinician rates it separately on the same scale. The total runs from 0 to 76, where lower means less active disease. Published thresholds sort scores into remission, low, moderate, and high disease activity. What distinguishes the CDAI is that it needs no blood test, so it can be calculated in the room during the visit.
Further Reading
Additional Notes
Learn More: The score bands are: ≤2.8 remission, >2.8 to ≤10 low, >10 to ≤22 moderate, >22 high disease activity. Meaningful change depends on where a person started — reported minimal clinically important differences are about −12 points from high activity, −6 from moderate, and −1 from low.