Frequency of serological markers of rheumatoid arthritis in patients with Hashimoto's thyroiditis.

Background: Hashimoto's thyroiditis (HT) is an autoimmune disease that is frequently associated with other autoimmune conditions.

Objective: To perform serological screening for rheumatoid arthritis (RA) in patients with HT.

Methods: Our study included 88 consecutive serum specimens of patients with confirmed HT and 88 sex- and age-matched healthy subjects. All study participants were tested for anti-cyclic citrullinated peptides antibodies (CCP-Ab) and rheumatoid factor (RF). CCP-Ab and RF were performed using ELISA commercial kits. Statistical analysis was conducted using Epi Info, version 3.

Results: Out of 88 patients with HT, 15 (17.0%) had CCP-Ab or RF. The frequency of serological markers of RA was significantly higher in patients than in control individuals (17.0% vs 4.5%; P = .007). RF was more frequent in patients than in the control group, and the difference was statistically significant (13.6% vs 3.4%; P = .01). Isolated RF-IgM was absent in all controls and present in 6 patients with HT (6.8% vs 0%; P = .02). Out of 14 male patients, 3 (21.4%) had antibodies of RA. There was no significant difference in age between patients with CCP-Ab or RF and those without.

Conclusion: A high frequency of serological markers of RA was highlighted in patients with HT.