Table 5 Relative odds ratios (ORs), with 95% confidence intervals (CIs), of rheumatoid factor positive rheumatoid arthritis between tertiles* of citrulline/arginine containing C/A (II) C-telopeptide antibody ratios in tertiles* of anti-CCP antibodies

Anti-CCP	C/A (II) ratio
	Lower		Medium		Higher
	n†	OR (95% CI)	n†	OR (95% CI)	n†	OR (95% CI)
Lower	5/27	1.00	8/25	2.93 (0.68 to 12.67)	12/34	3.87 (0.95 to 15.73)
Medium	1/22	0.31 (0.03 to 3.26)	6/31	1.99 (0.39 to 10.08)	15/35	6.70 (1.49 to 30.01)
Higher	9/34	1.76 (0.36 to 8.69)	4/31	1.10 (0.18 to 6.69)	29/21	20.06 (4.37 to 92.06)

*The tertiles are based on the distributions among controls; †n = number of cases/controls.
p value for interaction = 0.02.