Sample selection

A total of 111 consecutive patients diagnosed to have RA according to the 2010 ACR/EULAR classification criteria for Rheumatoid arthritis¹⁰ were included in the study and compared with 97 healthy controls matched for age and gender. Informed consent was obtained from each participant included in this study according to the declaration of Helsinki. Ethical approval was obtained from the Ethics Committee in Medical Department, College of Medicine, Baghdad University.

Patients with the following conditions were excluded from the study: if they had other autoimmune connective tissue diseases like systemic sclerosis, systemic lupus erythematosus, and inflammatory arthritis like ankylosing spondylitis, inflammatory bowel diseases and psoriatic arthritis, acute or chronic infection, malignant diseases, renal and liver disease, haematological disorders such as iron deficiency anemia or had received blood transfusion during the past 4 months, cardiovascular and metabolic diseases, cerebrovascular disease, hypo- or hyperthyroidism, pregnancy or 6 months during postpartum period.