Background Rheumatoid arthritis (RA) is a chronic inflammatory polyarthritis with a prevalence of 0.5–1% of general population. Various comorbidities can complicate the course of the disease and have direct effects on the long-term prognosis and management of RA. Previous studies showed that there is an increased prevalence of thyroid disease (TD) among RA patients, probably due to autoimmunity; however the association of RA disease characteristic and TD has not been evaluated before.
Objectives To determine the association between TD and RA and reveal the prevalence of TD among RA patients.
Methods All patients diagnosed with RA since 1st of January 2010 were included in this cross sectional study. Patients' demographic data (age, sex, year of diagnosis), serology test results including rheumatoid factor (RF), anti-cyclic citrullinated peptide antibody (anti-ccp) and antinuclear antibody (ANA) as well as disease activity score in 28 joints (DAS28) at the time of diagnosis and after 4 months (±1–2 months) of treatment were extracted in December 2015. Patients' previous medical history as well as medications and laboratory tests were evaluated to find out if the patients have been diagnosed with thyroid disease as well. Patients with subclinical thyroid diseases were also considered to perform statistical analysis. Chi-square test and t-test were used to compare different variables in patients with/without TD.
Results Of 439 included patients 60.14% were female. The mean of age and disease duration were 64.64±15.03 and 2.59±1.66 years respectively. Prevalence of TD was 69/439 (15.7%). The mean of ΔDAS28 in patients with simultaneous TD and RA was 1.0±1.4 and in patients with isolated RA 1.5±1.4 (P<0.05). The results of our study showed that presence of TD among RA patients is associated with female gender (P<0.001), ANA positivity (P<0.05) and anti-ccp ≥100 AU/ml (P=0.05). Furthermore, coexistence of TD and RA resulted in poor response to treatment (P<0.05). We did not find any association between TD and disease duration as well as RF positivity.
Conclusions Considering the higher prevalence of TD among RA patients in comparison with general population, we recommend the routine measurement of thyroid stimulating hormone to detect TD at an earlier stage, leading to earlier treatment initiation and improve prognosis.
Gabriel SE, Michaud K. Epidemiological studies in incidence, prevalence, mortality, and comorbidity of the rheumatic diseases. Arthritis Research & Therapy. 2009;11:229.
Dougados M, Soubrier M, Antunez A, et al. Prevalence of comorbidities in rheumatoid arthritis and evaluation of their monitoring: results of an international, cross-sectional study (COMORA). Ann Rheum Dis. 2014;73:62–8.
Pan XF, Gu JQ, Shan ZY. Increased risk of thyroid autoimmunity in rheumatoid arthritis: a systematic review and meta-analysis. Endocrine. 2015;50:79–86.
Acknowledgement We thank Danbio https://danbio-online.dk/.
Disclosure of Interest None declared