Anti-citrullinated peptide autoantibodies, human leukocyte antigen shared epitope and risk of future rheumatoid arthritis: a nested case–control study

Table 3 Odds ratios for rheumatoid arthritis by anticitrullinated peptide autoantibody positivity and presence of HLA-SE ^a

	ACPA-negative			ACPA-positive
Parameter	Cases (N = 36)	Controls (N = 268)	OR (95% CI)	Cases (N = 27)	Controls (N = 15)	OR (95% CI)	OR (95% CI) for ACPA within strata of *HLA-SE*
HLA-SE absent	17	153	1.0 (ref)	6	8	7.7 (2.2 to 27.5)	7.7 (2.2 to 27.5)
						P = 0.002	P = 0.002
HLA-SE present	19	115	1.4 (0.7 to 2.9)	21	7	33.3 (11.1 to 99.6)	23.8 (7.9 to 71.8)
			P = 0.38			P < 0.0001	P < 0.0001
OR (95% CI) for HLA-SE present			1.4 (0.7 to 2.9)			4.3 (1.0 to 18.6)
within strata of ACPA			P = 0.38			P = 0.05

^aACPA: anticitrullinated antibody, CI: confidence interval, HLA-SE: human leukocyte antigen shared epitope, OR, odds ratio, ref: reference value. Measure of effect modification on the additive scale: Synergy Index = 4.5 (95% CI = 0.9 to 21.6; P = 0.06). Measure of effect modification on the multiplicative scale: ratio of odds ratios = 3.1 (95% CI = 0.6 to 15.8; P = 0.18). ORs estimated by logistic regression models adjusted for matching factors and age at blood draw, alcohol intake, body mass index, regularity of menses and pack-years of smoking. Restricted to cases with blood draw less than 5 years before diagnosis (cases = 63, controls = 283) in the Nurses’ Health Study and Nurses’ Health Study II.

ISSN: 1478-6362