Relationship of fibrinogen-like protein 1 (FGL 1) level with disease activity in patients with adult rheumatoid arthritis

Rheumatoid arthritis is an inflammatory and autoimmune disease that can involve primarily joints, but also pulmonary, cardiovascular, ocular and cutaneous. Complications caused by inflammation in rheumatoid arthritis are associated with morbidity and mortality. Multiple biomarkers such as RF, Anti-CCP, CRP, ESH are used together with clinical findings to diagnose RA and evaluate disease activity. The focus of current studies is the discovery of new biomarkers that can be used alone or to support existing biomarkers in both diagnosis and activity evaluation in RA. Fibrinogen Like Protein 1 (FGL1) is a member of the fibrinogen superfamily secreted primarily from hepatocytes. Studies have shown that FGL1 has the ability to act as an acute phase protein and FGL1 is an important inhibitory ligand for lymphocyte activation gene 3 (LAG-3), an immune inhibitory receptor on antigen-specific T cells. Therefore, FGL1 may be a new marker in the diagnosis of an autoimmune disease characterized by chronic inflammation, such as RA, and in the follow-up of disease activity. In our study, we aimed to investigate the relationship of FGL1 levels with disease diagnosis, disease activity, CRP, and ESR in adult RA patients. Our study included 54 active RA patients, 54 remission RA patients, and 56 healthy men and women aged 18-65 years. Individuals with heart failure, history of malignancy, history of acute infection, chronic liver disease, amyloidosis, thyroid disease, pregnancy status, history of acute coronary syndrome in the last six months, chronic renal failure patients with GFR <60 ml/min and additional rheumatological diseases were not included in the study. Serum FGL1 level was found to be statistically significantly higher in the RA patient group than in the control group, and in active RA patients compared to RA patients in remission. There was a positive correlation between FGL1 level and CRP, ESR, CRP/Albumin levels. It was determined that the increase in serum FGL1 levels increased the possibility of RA diagnosis. It was found that the increase in serum FGL1 levels increased the probability of detecting active RA patients. As a result, we think that serum FGL1 levels can be used as a new marker in the diagnosis of RA and in the evaluation of disease activity.