TABLE 2.

Composite Disease Activity Measurement^a,b

Formulas for calculation of recommended composite measures

SDAI = TJC + SJC + PGA + EGA + CRP

CDAI = TJC + SJC + PGA + EGA

Disease activity cutoffs
	Absolute disease activity level
Index	Remission	Low	Moderate	High
SDAI	≤3.3	≤11	≤26	>26
CDAI	≤2.8	≤10	≤22	>22

^aCDAI = Clinical Disease Activity Index; CRP = C-reactive protein (mg/dL); EGA = Evaluator Global Assessment (0-100 mm); PGA = Patient Global Assessment (0-100 mm); SDAI = Simplified Disease Activity Index; SJC = No. of swollen joints using a 28-joint count; TJC = No. of tender joints using a 28-joint count.

^bMeasurement of disease activity at each point in time should be based on quantitative assessments and summarized using a composite disease activity instrument. We use the SDAI for patients with increased acute-phase reactant levels, and for all others we use the CDAI. Note that the SDAI requires that CRP values be given in milligrams per deciliter. When calculating the SDAI for a patient with CRP reported as less than the detectable range (ie, <0.3 mg/dL), we input a value of 0.29 for the calculation. To convert CRP mg/dL value to nmol/L, multiply by 95.24.

Adapted from Best Pract Res Clin Rheumatol,²⁸ with permission.