Table 1.
Characteristics of the patients with RA included in the study.
Fig 1.
Distribution of patients with RA positive for the different autoantibodies.
We observed that anti-CarP antibodies were not associated with the SE alleles (Fig 2A). This lack of association was found in all analyses performed, which included either all the SE alleles together (OR = 1.1, P = 0.6), or only the HLA-DRB1*01 alleles (OR = 0.9, P = 0.7), or the *04 alleles (OR = 1.0, P = 0.9), or the *1001 allele (OR = 1.2, P = 0.7). In addition, we did not observe association in analyses conditional on the anti-CCP status (OR = 0.8, P = 0.4), the RF status (OR = 0.9, P = 0.6) or both (OR = 0.8, P = 0.3). In a similar way, there was no association of the anti-CarP status with the PTPN22 R620W polymorphism (Fig 2B). Again, this result was consistent in the direct analysis (OR = 0.9, P = 0.7), and in the conditional on other autoantibodies (OR = 0.8, P = 0.5 conditional on anti-CCP; OR = 1.0, P = 0.8 conditional on RF; and OR = 0.9, P = 0.7 conditional in the two other autoantibodies). Finally, we did not observe association of the anti-CarP antibodies with smoking (OR = 1.0, P = 0.9; Fig 2C). We should note that the anti-CCP positive status was associated with the SE alleles (P = 2.4 x 10−7), showed a stronger association than the anti-CCP negative status with the PTPN22 R620W polymorphism (P = 0.002 for anti-CCP positive and P = 0.13 for anti-CCP negative patients), but it was not associated with smoking (P = 0.65) in our patients, as we already have noted previously [16,17]. All these analyses were adjusted for gender, age at disease onset and time of follow-up.
Fig 2.
Stratified analysis of RA risk factors according to the anti-CarP and anti-CCP status.
Frequency of the A) HLA-DRB1 SE and B) PTPN22 R620W genotypes in the different strata. White fraction = heterozygotes, grey fraction = homozygotes. C) Frequency of ever smokers. Error bars represent 95% CI. Crl. = controls, NA = not available. P values were obtained with logistic regression analysis adjusted for gender, age of diagnosis and time of follow-up.
Fig 3.
Prevalence of RA bone erosions in anti-CCP and anti-CarP defined subgroups.
Error bars represent 95% CI. P value from logistic regression analysis adjusted for gender, age of diagnosis and time of follow-up.