Table 4.

Assessing the difference in familial aggregation of RA by ACPA versus RF serology: cases from the EIRA study

RA in FDR	Serology in proband	Seropositive RA in case		Seronegative RA in case		Ratio of ORs (95% CI)
		FDRs with RA, N (%) Cases/controls	OR (95% CI)	FDRs with RA, N (%) Cases/controls	OR (95% CI)
Seropositive	RF	155 (2.0)/185 (0.5)	4.27 (3.28 to 5.55)	48 (1.2)/114 (0.6)	1.93 (1.35 to 2.77)	2.21 (1.42 to 3.44)
Seropositive	ACPA	166 (2.2)/198 (06)	4.29 (3.30 to 5.57)	38 (0.9)/101 (0.5)	1.71 (1.17 to 2.49)	2.51 (1.59 to 3.98)
Seropositive	RF and ACPA	143 (2.3)/165 (0.6)	4.45 (3.35 to 5.91)	28 (1.0)/80 (0.6)	1.54 (0.99 to 2.41)	2.88 (1.70 to 4.88)
Seronegative	RF	24 (0.3)/61 (0.2)	2.07 (1.25 to 3.41)	15 (0.4)/35 (0.2)	2.24 (1.20 to 4.17)	0.92 (0.42 to 2.05)
Seronegative	ACPA	26 (0.4)/63 (0.2)	2.24 (1.38 to 3.64)	15 (0.4)/35 (0.2)	2.15 (1.16 to 3.98)	1.04 (0.48 to 2.28)
Seronegative	RF and ACPA	21 (0.3)/51 (0.2)	2.26 (1.32 to 3.87)	12 (0.4)/25 (0.2)	2.52 (1.26 to 5.04)	0.89 (0.37 to 2.15)

ACPA, anticitrullinated peptide antibodies; FDR, first-degree relative; RA, rheumatoid arthritis; RF, rheumatoid factor.