Table 3.

Risk of antibody-positivity predicted by HLA-SE, smoking and HLA-SE+smoking in patients with RA and their first-degree relatives

	Patients with RA			First-degree relatives
Antibody	SE	Smoking ever	SE+smoking ever	SE	Smoking ever	SE+smoking ever
IgG-ACPA	4.71 (1.84 to 12.05)	2.17 (0.90 to 5.23)	19.33 (2.54 to 147.21)*	0.55 (0.25 to 1.21)	1.37 (0.63 to 2.95)	0.71 (0.28 to 1.81)
IgA-ACPA	2.03 (0.96 to 4.30)	1.89(0.94 to 3.79)	2.81 (1.27 to 6.24)	0.47 (0.22 to 0.97)	1.36 (0.65 to 2.85)	0.76 (0.31 to 1.86)
IgM-ACPA	1.30 (0.64 to 2.63)	2.33(1.21 to 4.48)	2.17 (1.07 to 4.00)	0.76 (0.35 to 1.64)	0.79 (0.36 to 1.73)	0.79 (0.31 to 2.02)
IgG+IgA+IgM-ACPA	1.78 (0.84 to 3.77)	2.39 (1.21 to 4.71)	2.98 (1.51 to 5.89)	0.20 (0.02 to 1.87)	1.14 (0.22 to 5.82)	0.71 (0.08 to 6.48)
IgM-RF	1.85 (0.86 to 4.0)	1.76 (0.87 to 3.58)	2.45 (1.10 to 5.46)	0.75 (0.30 to 1.88)	0.75 (0.30 to 1.88)	0.43 (0.12 to 1.54)
IgA-RF	1.36 (0.62 to 2.96)	2.31 (1.11 to 4.78)	2.23 (0.99 to 4.98)	1.11 (0.51 to 2.38)	1.61 (0.73 to 3.55)	1.21 (0.50 to 2.94)
IgM+IgA-RF	1.47 (0.71 to 3.05)	2.16 (1.11 to 4.23)	2.53 (1.21 to 5.28)	0.58 (0.18 to 1.93)	0.97 (0.31 to 3.03)	0.24 (0.03 to 1.91)

Values are OR (95% CI).

^*All ever-smoking patients with RA with SE had IgG isotype antibodies. To permit this calculation, one of these patients was recorded as IgG negative.

ACPA, anti-citrullinated protein/peptide antibody; HLA, human leucocyte antigen; RA, rheumatoid arthritis; SE, shared epitope.