Can anti-cyclic citrullinated peptide antibody-negative RA be subdivided into clinical subphenotypes?

Table 1 Baseline characteristics of the study population and the factors found in PCA

		Component
Variable	Baseline frequency	1	2	3	4	5	6	7	8	9
Age at inclusion (years, mean ± SD)	59.2 (16.2)	0.761
Female gender (n, %)	219 (68.9)	0.448			0.394
Subacute onset of symptoms (versus insidious)	188 (59.1)			0.592		-0.306			0.316
Morning stiffness (min; mean ± SD)	103.18 (112.0)				-0.496			0.484
Fatigue (VAS; mean ± SD)	45.1 (29.9)	-0.389					0.522
Symptom duration (days; mean ± SD)	172.1 (180.2)			0.394		-0.349			0.455
Family history of RA (n, %)	62 (19.5)	-0.326		0.594		0.380
Past or present smoking (n, %)	128 (40.3)				0.652			0.375
Fever (n, %)	22 (6.9)							-0.319		-0.426
Involvement of small/large joints (n, %)	^a		0.604
Symmetry of involved joints (n, %)	216 (67.9)		-0.379		0.308	0.331				0.370
Involvement of upper/lower extremities	^b		0.602			-0.348
Inflammatory back pain (n, %)	16 (5.0)						0.466	0.531		0,321
Skin abnormalities (N, %)^c	56 (18.1)			0.374
Swollen joint count (mean ± SD)^d	11.3 (8.5)		0.445	0.365
CRP (mg/L; mean ± SD)	30.10 (34.4)	0.315	0.434							0.512
RF (IU/ml) (mean ± SD)^e	7.12 (19.5)				0.305	-0.345	0.315		-0.602
MCV positivity (n, %)	59 (18.6)			0.470	0.376		-0.321
Erosive disease at baseline (n, %)	202 (63.5)	0.642					0.332
Explained variance per component (%)		10.0	8.6	8.0	7.4	6.8	6.5	5.6	5.5	5.4

Involvement of upper extremities: shoulder, elbow, wrist, or hand joints; involvement of lower extremities: joints of hip, knee, ankle, feet or toe joints.^aInvolvement of small/large joints: in 163 patients (51.3%), only small joints of hands and feet were involved. In 53 patients (16.7%) only large joints were involved. In 93 patients (29.2%), both small and large joints were involved.^aInvolvement of upper/lower extremities: in 156 patients (49.1%) only joints in the upper extremities were involved. In 28 patients (8.8%), only joints in the lower extremities were involved. In 96 (30.2%) patients, joints in both lower and upper extremities were involved.^cSkin abnormalities: absence or presence of dermatological abnormalities such as psoriatic lesions, ulcers, rheumatoid nodules and so on.^dSwollen Joint Count: 44-Swollen Joint Count.^eAnalyses were performed on RF in groups (less than reference value, 1 to 3 times reference value, or more than 3 times reference value). CRP, C-reactive protein; MCV, mutated citrullinated vimentin; RF, rheumatoid factor; VAS, visual analogue scale.

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