Table 2

Factor analysis: principal component analysis using Varimax rotation

	Component (Eigenvalue)
	1 (5.33)	2 (1.91)	3 (1.62)	4 (1.15)	5 (0.99)	6 (0.94)
Serology
Anti-CCP (0, 1, 2)^*	0.104	0.064	0.035	0.079	0.094	0.878
Rheumatoid factor (0, 1, 2)^*	0.105	0.013	0.064	0.053	0.117	0.878
Acute phase measures
CRP (0, 1, 2)^*	–0.004	0.101	–0.049	0.847	0.004	0.055
ESR (tertiles)	0.012	0.026	–0.042	0.847	–0.042	0.121
Functional measures
HAQ (tertiles)	0.103	0.180	0.343	0.555	0.062	–0.074
Joint swelling
SJC (1, 2–6, 7–28)	0.612	0.356	0.198	0.075	0.526	0.125
MCP swelling (yes/no)	0.839	0.103	0.282	0.017	0.149	0.158
PIP swelling (yes/no)	0.287	0.138	0.082	–0.003	0.852	0.176
Wrist swelling (yes/no)	0.165	0.865	0.140	0.119	0.055	0.102
MTP swelling (yes/no)	0.055	0.047	0.024	0.009	0.022	0.127
Joint tenderness
Tender joint count (1, 2–6, 7–28)	0.268	0.204	0.767	0.058	0.384	0.047
MCP tenderness (yes/no)	0.509	0.014	0.723	–0.003	0.108	0.094
PIP tenderness (yes/no)	0.103	0.045	0.550	–0.048	0.710	0.098
Wrist tenderness (yes/no)	0.001	0.658	0.599	0.036	0.001	0.048
Symmetry of joint involvement
Symmetrical MCP swelling	0.826	0.205	0.095	0.039	0.163	0.062
Symmetrical wrist swelling	0.229	0.785	–0.024	0.133	0.194	–0.037
Theme	MCP involvement	Wrist involvement	Hand/finger tenderness	Acute phase response	PIP involvement	Serology
Test variable for subsequent analysis	MCP swelling	Wrist swelling	PIP or MCP or wrist tenderness	CRP or ESR (low/mod/high)	PIP swelling	Anti-CCP or ESR (low/mod/high)

↵* Categories defined as follows: 0, normal by local standards; 1, below the median of non-normal values; 2, above the median of non-normal values.
anti-CCP, anti-cyclic citrullinated protein; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; HAQ, Health Assessment Questionnaire; MCP, metacarpophalangeal; MTP, metatarsophalangeal; PIP, proximal interphalangeal; SJC, swollen joint count.
Loadings of >0.6 are highlighted in bold to facilitate the interpretation.