Table 1

Concentration of the different isotypes of CCP2 antibodies (AU/ml) and RFs (IU/ml) in healthy controls, patients with RA and first-degree relatives

	IgG-CCP2	IgA-CCP2	IgM-CCP2	IgM-RF	IgA-RF
Controls (n=100)	1.5	0.6	18.5	0.8	3.4
IQR	(1.0–2.2)	(0.4–0.7)	(9.6–30.9)	(0.6–1.2)	(2.7–4.7)
First-degree relatives (n=157)	2.2^***	1.0^***	27.9^***	1.3^***	4.7^***
IQR	(1.4–3.1)	(0.7–1.5)	(13.7–53.3)	(0.9–2.4)	(3.4–8.0)
RA patients (n=163)	235.0^***	2.8^***	51.7^***	29.9^***	24.6^***
IQR	(27.0–569.0)	(1.3–13.0)	(22.5–140.0)	(4.6–134.3)	(8.8–60.3)
p Value^†	<0.001	<0.001	<0.001	<0.001	<0.001

Values are median (Q1–Q3).
↵*** p<0.001, refers to post-hoc comparisons between first-degree relatives or RA patients versus controls.
↵† Kruskal–Wallis test for three independent samples.
CCP, cyclic citrullinated peptide; RA, rheumatoid arthritis; RF, rheumatoid factor.