Low levels of antibodies against common viruses associate with anti-citrullinated protein antibody-positive rheumatoid arthritis; implications for disease aetiology

Table 4 Association and additive interaction between HLA-DRB1 SE alleles and anti-viral antibodies in ACPA-positive RA

Factors		Cases (%)	Controls (%)	OR (95% CI)^a
HLA-DRB1 SE	EBV
-	high^b	17 (2.83)	76 (11.00)	1.0 ref
-	low^c	76 (12.67)	273 (39.51)	1.2 (0.6–2.1)
+	high	85 (14.17)	97 (14.03)	3.9 (2.1–7.2)
+	low	422 (70.33)	245 (35.46)	7.9 (4.5–13.8)
AP (95% CI)		0.5 (0.3–0.7)
HLA-DRB1 SE	B19
-	high	9 (1.50)	77 (11.14)	1.0 ref
-	low	84 (14.00)	272 (39.36)	2.7 (1.3–5.7)
+	high	92 (15.33)	96 (13.89)	8.8 (4.1–18.8)
+	low	415 (69.17)	246 (35.60)	15.7 (7.7–32.2)
AP (95% CI)		0.3 (0.1–0.5)
HLA-DRB1 SE	CMV
-	high	17 (2.84)	88 (12.75)	1.0 ref
-	low	76 (12.69)	261 (37.83)	1.5 (0.9–2.8)
+	high	125 (20.87)	86 (12.46)	8.2 (4.5–15.0)
+	low	381 (63.60)	255 (36.96)	8.4 (4.8–14.6)
AP (95% CI)		-0.05 (-0.4–0.3)

ACPA anti-citrullinated protein antibody, RA rheumatoid arthritis, AP attributable proportion due to additive interaction, CI confidence interval, EBV Epstein-Barr virus, CMV cytomegalovirus, ref reference
^aOdds ratios (OR) were adjusted for age, gender, and residential area. Significant ORs are shown in italics
^bHigh indicates highest quartile of antibody titres (25% highest)
^cLow indicates lower three quartiles of antibody titres (75% lowest)

ISSN: 1478-6362