PRTN3 and rheumatoid arthritis: In a binary logistic regression analysis adjusting for age, gender, smoking, and serum IgG ACPA, there was still a significant association between the level of IgA anti-RgpB in saliva and RA, with 1.3% increased risk for having RA per increased unit of IgA anti-RgpB [odds ratio (OR) = 1.013; 95% confidence interval (CI), 1.002–1.024; p = 0.022].