Table 3

Demonstration of the domains contained in various composite disease activity measures in comparison with the variables loading best in the principal component analysis

	Composite scores
	Two highest loading variables per component	DAS28	SDAI	CDAI	DAREA
Component I: Patient self-reported disease activity	VAS PtGA	+	+	+	+
	VAS PAIN	−	−	−	+
Component II: Joint counts	66 SJC	−*	−*	−*	+
	68 TJC	−*	−*	−*	+
Component III: Acute phase reactants	CRP	−**	+	−	+
Component III: Acute phase reactants	ESR	+	−	−	−

↵* Based on 28 joint counts.
↵** DAS28 has been modified for the use of CRP rather than ESR but this is not sufficiently validated.
CDAI, clinical disease activity index; CRP, C-reactive protein; DAREA, Disease Activity index for REactive Arthritis; DAS28, disease activity index based on 28 joint count; ESR, erythrocyte sedimentation rate; SDAI, simplified disease activity index; SJC, swollen joint count; TJC, tender joint count; VAS PAIN, visual analogue scale patient pain assessment; VAS PtGA, visual analogue scale patient global disease activity assessment;