Background There have been little data regarding epidemiology and usefulness of autoantibodies in general population.
Objectives The purpose of this study is to describe epidemiological data about rheumatoid factor (RF) and anti-CCP antibody (ACPA) in Japanese general population and evaluate the usefulness of ACPA for detecting undiagnosed RA at annual health checkup.
Methods During the period from November 2013 to January 2014, we checked RF and ACPA in all the female who visited St. Luke's International Hospital Center for Preventive Medicine for annual health examinations. Patients who already had diagnosis of RA were excluded. Patients who had positive RF and/or ACPA are encouraged to visit our Rheumatology Clinic. First, we analyzed clinical characteristics of ACPA positive population. Then we divided seropositive referred patients into 3 groups; patients with positive RF and negative ACPA (Group A), patients with negative RF and positive ACPA (Group B), and patients who were positive for both of RF and ACPA (Group C). Rheumatology specialists examined all the referred patients and diagnosed them as either of RA, undifferentiated arthritis, or asymptomatic seropositive patient.
Results During the study period, 3,610 consecutive Japanese female were checked RF and ACPA. The mean age was 49.9±24.5 yrs. The number of the seropositive patients for RF and ACPA are 397 (11.0%) and 53 (1.5%), respectively. Among them, 33 patients were positive for both of RF and ACPA. By multivariate analysis, ACPA positive population showed significant higher prevalence of positive RF (OR 11.7, 95% CI 6.35-21.69) and malignancy (OR 2.20, 95% CI 1.08-4.46) than those who with negative ACPA. Twenty-one of Group A, 3 of Group B, and 9 of Group C were referred to our Rheumatology Clinic. Among them, 4 (44.4%) of Group C are newly diagnosed as RA at first visit, while none of Group A and Group B were diagnosed as RA. In addition, 2 (9.5%) of Group A, 1 of Group B (33.3%), and 3 (33.3%) of Group C were diagnosed as undifferentiated arthritis. The specificities of RF and ACPA for detecting undiagnosed RA in referred patients were 10.3% and 72.4%, respectively.
Conclusions In general population, non-RA ACPA positive female showed higher prevalence of positive RF and malignancy. In addition, ACPA showed high specificity for detecting undiagnosed RA in referred patients.
Disclosure of Interest None declared