Clinical Disease Activity Index (CDAI)

The CDAI is a useful clinical composite score for following patients with rheumatoid arthritis. 

CDAI = SJC(28) + TJC(28) + PGA + EGA

  • SJC(28): Swollen 28-Joint Count (shoulders, elbows, wrists, MCPs, PIPs including thumb IP, knees)
  • TJC(28): Tender 28-Joint Count (shoulders, elbows, wrists, MCPs, PIPs including thumb IP, knees)
  • PGA: Patient Global disease Activity (patient’s self assessment of overall RA disease activity on a scale 1-10 where 10 is maximal activity)
  • EGA: Evaluator’s Global disease Activity (evaluator’s assessment of overall RA disease activity on a scale 1-10 where 10 is maximal activity)

Interpretation

  • Remission                               CDAI ≤ 2.8
  • Low Disease Activity             CDAI > 2.8 and ≤ 10
  • Moderate Disease Activity    CDAI > 10 and ≤ 22
  • High Disease Activity            CDAI > 22

    A CDAI reduction of 6.5 represents moderate improvement.

Deficiencies

  • Does not include the ankles / feet
  • Does not include inflammatory markers (although this is what makes it a quick and useful clinical tool)