Ab0579 the Coexistence of Anti-Thyroid Antibodies in Patients With Rheumatoid Arthritis Is Associated With an Increased Autoimmune Burden, Including Rheumatoid Factor and Antinuclear Antibodies

Background: Rheumatoid arthritis (RA) is a systemic autoimmune disease with multi-organ involvement. Immune-mediated thyroid disease is the most common organ-specific autoimmune disease in the general population. Although previous studies have shown an increased prevalence of autoimmune thyroid disease in patients with RA, the relationship of autoimmune thyroid disease, and its corresponding specific autoantibodies, with clinical features of RA patients remains unknown. Objectives: To determine the prevalence of thyroid autoantibody (acT) positivity in patients with RA and to analyze the relationship between the presence of thyroid autoimmune disease, and its organ-specific autoantibodies, and the clinical expression of RA. Methods: Cross-sectional study that encompassed 755 RA patients. Thyroid function (TSH, T4L) and antiperoxidase and antithyroglobulin acT were determined (according to a specific protocol in which the latter are only determined if the former are negative). For the purposes of this study, the presence of any of them was considered acT positivity. Multivariable logistic and linear regression were used to analyze the relationship between these acT and disease characteristics, including, among others, the clinical activity of the disease and the presence of rheumatoid factor and anti-citrullinated peptide and antinuclear antibodies. Results: Seventeen percent (130) of RA patients showed acT positivity. While 92% of the patients had normal thyroid function, 4 and 5% of them had thyroid hormone levels compatible with hyper- and hypothyroidism, respectively. Demographics, comorbidities and disease-related characteristics, separated by the presence or absence of acT, are shown in Table 1. In this regard, acT-negative patients were significantly more often male (27 vs. 15 %, p=0.003) and tended to have a longer disease duration (3.7 [1.4-9.6] vs. 3.0 [1.2-7.0] years, p=0.069). No differences were observed between the two groups in the distribution of other characteristics such as cardiovascular risk factors. Regarding RA-related characteristics, the presence of acT was associated with a higher frequency of rheumatoid factor (51 vs. 62 %, p=0.028) and antinuclear antibodies (16 % vs. 27, p=0.004). These relationships were maintained after adjustment for covariates. Moreover, the presence of anti-citrullinated peptide antibodies tended to be higher in acT-positive patients, although, in this case, statistical significance was not reached (51 vs. 58 %, p=0.18). Besides, other disease characteristics such as acute phase reactants, activity indices, presence of erosions or extra-articular manifestations and the use of certain therapies were not significantly different between acT and non-acT patients. Conclusion: 17% of RA patients are acT-positive. The presence of these acTs is associated with a higher autoimmune burden in terms of a significantly increased frequency of rheumatoid factor and positive antinuclear antibodies. However, in this cross-sectional study, no relationship was observed between the presence of these acTs and other disease characteristics such as clinical disease activity, acute phase reactants, radiological damage or extra-articular manifestations. REFERENCES: NIL. Table 1. Demographic, clinical features and laboratory parameters differences between AcT positive and negative group in 755 RA patients. (*) Multivariate analysis adjusted for sex and disease duration. Acknowledgements: NIL. Disclosure of Interests: None declared.