Rheumatoid factor is a marker of disease severity in Korean rheumatoid arthritis.

Serum rheumatoid factor (RF) is important in the diagnosis and prognosis of rheumatoid arthritis (RA). The purpose of this study is to compare the clinical characteristics and treatment patterns of RA according to the presence of RF in Korean patients. A retrospective analysis was performed on the records of 109 patients who were followed for at least 2 years, among 230 RA patients who visited at the rheumatology clinic in Ajou University Hospital and who fulfilled the 1987 revised American College of Rheumatology criteria for RA. Sixty-four patients were RF positive (58.7%) and 91 patients were female (83.5%). There was no significant difference in demographic characteristics, joint involvements, or percentage of morning stiffness between seropositive and seronegative groups. Antinuclear antibody was detected more frequently in the seropositive group (p < 0.05). At initial diagnosis, the seropositive group had higher white blood cell and platelet counts than the seronegative group (p < 0.01). However, the difference was disappeared at the last follow-up. Inflammatory markers such as ESR and CRP were also higher at diagnosis in the seropositive group (p < 0.01). These inflammatory markers were still greater than the seronegative group at the last follow-up (p < 0.01). There was no significant difference in the use of disease modifying antirheumatic drug (DMARD) and steroid dosage between groups. However, DMARD combination therapy was more commonly used in the seropositive group (p < 0.05), especially triple DMARD combination. These results suggest that disease activity is more severe in the seropositive than the seronegative group, and more aggressive treatments are needed in the seropositive group.