What instruments are used to measure Rheumatoid Arthritis disease activity?
There are several validated instruments that can be used to measure disease activity. Each uses various combinations of tender (TJC) and swollen joint count (SJC), patient global assessment of disease (PtGA), physician global assessment of disease (PhGA), patient pain, CRP or ESR, and the multidimensional health assessment questionnaire (MDHAQ). The most important thing is that disease activity is measured; the type of instrument used is of less importance. The instruments commonly used are shown in the below table.
| Instrument (Score Range) | Remission | Low Disease Activity | Moderate Disease Activity | Severe Disease Activity |
|---|---|---|---|---|
| DAS28 (0–9.4) | ≤2.6 | ≤3.2 | >3.2 to ≤5.1 | >5.1 |
| SDAI (0–86) | ≤3.3 | ≤11 | >11 to ≤26 | >26 |
| CDAI (0–76) | ≤2.8 | ≤10 | >10 to ≤22 | >22 |
| RAPID3 (0–30) | ≤1 | <6 | ≥6 to ≤12 | >12 |
CDAI, clinical disease activity index; DAS28, disease activity score in 28 joints; RAPID3, routine assessment of patient index data; SDAI, simplified disease activity index.
Disease activity score in 28 joints (DAS28): calculate using the DAS calculator ( www.das-score.nl ). Components: TJC, SJC, ESR, PtGA.
Simplified disease activity index: TJC (0–28) + SJC (0–28) + PtGA (0–10) + PhGA (0–10) + CRP (mg/dL)
Clinical disease activity index: TJC (0–28) + SJC (0–28) + PtGA (0–10) + PhGA (0–10)
Routine assessment of patient index data: MDHAQ (0–10) + patient pain (0–10) + PtGA (0–10)
There are a growing number of studies supporting biomarker assessment (cytokine and chemokine panels) and/or imaging studies such as ultrasound (assessment for power-doppler signal to the joints and/or evidence of gray-scale synovitis) as useful tools in determining disease activity. The exact role of these instruments in routine clinical practice remains to be determined.
