Table 3.

Baseline characteristics of cohort by anti-CCP antibody status^*

	All IP patients			IP patients assessed at 5 years
	Anti-CCP antibody negative (n = 648)	Anti-CCP antibody positive (n = 268)	P	Anti-CCP antibody negative (n = 515)	Anti-CCP antibody positive (n = 214)	P
Age at symptom onset, years†	52 (39–66)	56 (48–66)	< 0.001	51 (40–64)	55.5 (47–64)	0.002
Women, no. (%)‡	431 (66.5)	152 (56.7)	0.005	356 (69.1)	129 (60.3)	0.023
Symptom duration at registration, months†	4 (2–10)	5 (2–10.5)	0.23	4 (2–10)	5 (2–10)	0.55
HAQ score (n = 910)†	0.625 (0.25–1.25)	0.88 (0.375–1.625)	< 0.001	0.625 (0.25–1.25)	0.875 (0.375–1.625)	0.003
CRP level, mg/liter (n = 845)†	3 (0–11)	12 (4–31)	< 0.001	3 (0–10)	10 (3–23)	< 0.001
DAS28 score (n = 845)†	3.73 (2.66–4.8)	4.4 (3.4–5.45)	< 0.001	3.76 (2.78–4.82)	4.41 (3.43–5.37)	< 0.001
Swollen joint count†	6 (2–12)	8 (4–16.5)	< 0.001	6 (2–12)	8 (4–16)	< 0.001
Tender joint count†	7 (2–16)	8 (4–16)	0.17	7 (2–17)	8 (4–16)	0.29
Swollen and tender joint count†	3 (0–8)	4 (1–9)	0.002	3 (0–8)	4 (1–9)	0.006
Satisfy ACR criteria for RA, no. (%)‡	241 (37.2)	194 (72.4)	< 0.001	203 (39.4)	155 (72.4)	< 0.001
Smoking status at baseline, no. (%)‡			0.001			0.025
Never smoked	221 (34.3)	69 (25.8)		180 (35.2)	60 (28)
Ex-smoker for ≥10 years	177 (27.5)	56 (21)		141 (27.6)	48 (22.4)
Ex-smoker for <10 years	90 (14.0)	55 (20.6)		70 (13.7)	42 (19.6)
Current smoker	156 (24.2)	87 (32.6)		120 (23.5)	64 (29.9)

^*Values are the median (interquartile range) unless otherwise indicated. Anti-CCP = anti–cyclic citrullinated peptide; IP = inflammatory polyarthritis; HAQ = Health Assessment Questionnaire; CRP = C-reactive protein; DAS28 = Disease Activity Score in 28 joints; ACR = American College of Rheumatology; RA = rheumatoid arthritis.

^†Kruskal-Wallis test was used to test significance between the groups.

^‡Chi-square test was used to test significance between the groups.