Peptidyl arginine deiminase type IV (PADI4) haplotypes interact with shared epitope regardless of anti-cyclic citrullinated peptide antibody or erosive joint status in rheumatoid arthritis: a case control study

Table 4 Interaction between PADI4 haplotypes and SE alleles in susceptibility to anti-CCP-positive and -negative RA*

	Controls, No	All RA cases		anti-CCP-positive RA		anti-CCP-negative RA
Subgroup		No.	OR (95% CI)	No.	OR (95% CI)	No.	OR (95% CI)
GTG and SE carriage	1,003	1,311		820		145
GTG-negative/SE-negative	245	109	1	50	1	18	1
GTG-negative/SE-positive	133	257	5.17 (3.57 to 7.48)	168	8.20 (5.23 to 12.85)	21	2.40 (1.18 to 4.89)
GTG-positive/SE-negative	399	320	1.89 (1.37 to 2.61)	176	2.32 (1.54 to 3.49)	53	1.80 (0.99 to 3.25)¶
GTG-positive/SE-positive†	226	625	7.46 (5.38 to 10.36)	426	11.63 (7.73 to 17.51)	53	4.10 (2.23 to 7.53)
Diplotype and SE carriage	1,003	1,311		820		145
ACC/ACC/SE-negative	245	109	1	50	1	18	1
ACC/GTG/SE-negative	290	217	1.72 (1.22 to 2.42)	122	2.14 (1.39 to 3.30)	33	1.52 (0.81 to 2.88)¶
GTG/GTG/SE-negative	109	103	2.39 (1.56 to 3.66)	54	2.85 (1.68 to 4.85)	20	2.58 (1.24 to 5.37)
ACC/ACC/SE-positive	133	257	5.19 (3.58 to 7.51)	168	8.24 (5.25 to 12.92)	21	2.41 (1.18 to 4.92)
ACC/GTG/SE-positive	179	428	6.23 (4.42 to 8.77)	298	9.87 (6.47 to 15.06)	31	2.90 (1.50 to 5.60)
GTG/GTG/SE-positive‡	47	197	12.74 (8.03 to 20.23)	128	19.45 (11.32 to 33.42)	22	9.59 (4.39 to 20.98)

* OR and 95% CI were adjusted for age, sex, and smoking. RA, rheumatoid arthritis; anti-CCP, anti-cyclic citrullinated peptide autoantibody; OR, odds ratios; CI, confidence intervals.
† The attributable proportion (95% CI) due to interaction was 0.16 (-0.10 to 0.42) in anti-CCP-positive RA and 0.19 (-0.26 to 0.63) in anti-CCP-negative RA.
‡ The attributable proportion (95% CI) due to interaction was 0.45 (0.20 to 0.71) in anti-CCP-positive RA and 0.61 (0.29 to 0.92) in anti-CCP-negative RA.
¶Association was not significant (P = 0.05 and P = 0.20, respectively).

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