Abstract
BACKGROUND/AIM: Rheumatoid factor (RF) and anticitrullinated peptide (anti-CCP) are specific for rheumatoid arthritis (RA) diagnosis. However, they could be positive in other diseases and even in healthy populations. The aim was to investigate the prevalence of positive RF and anti-CCP antibodies in persons admitted to hospital for any reason and on a national scale. MATERIALS AND METHODS: The National Electronic Health Database, which contains the clinical records of over 80 million people, was used to design this multicenter, retrospective cohort study. The subjects included in the study were divided into age groups according to 10-year periods. RA cases were identified using ICD-10 codes that included M05, M06, M08, and their subgroups. RF and anti-CCP positivity were evaluated in terms of their contribution to the risk of being diagnosed with RA, with the change according to age and sex. RESULTS: During the 1.1.2018-31.12.2021 period, 13,918,072 RF tests were performed in 11,849,440 people, whereas 1,183,607 anti-CCP tests were performed in 1,020,967 people. Moreover, 797,089 people had both tests performed at least once. The RF positivity rate in patients who only requested RF tests was 14.72% and it was 35.04% for anti-CCP positivity in those who only requested anti-CCP tests. The rate of concomitant RF and anti-CCP positivity was 22.56%. An RA diagnosis was made in 27.8% of RF-positive people, 39.73% of anti-CCP-positive people, and 56.6% of co-RF and anti-CCP-positive people. RF positivity and concomitant RF and anti-CCP positivity increased with age and were more common in females. CONCLUSION: RF and anti-CCP positivity may be seen in a healthy population with female predominance. As age increases, the risk of RF positivity rises, but anti-CCP positivity does not change. Concomitant RF and anti-CCP positivity shows the highest risk of RA development with respect to either antibody positivity alone.