Examining the presence of RA in patients with and without the presence of certain antibodies in the blood

This study compared the severity of inflammation in rheumatoid arthritis (RA) patients with (seropositive) and without (seronegative) certain antibodies in their blood. The authors concluded that seronegative patients had higher levels of inflammation than seropositive patients.

RA is diagnosed based on a number of factors. A doctor will carry out a physical examination and consider any symptoms that are present in a patient. Levels of pain and the presence of swollen joints are some of the indicators of RA. Blood tests are also carried out to look for the presence of certain antibodies. Patients who have these antibodies are known as seropositive. Seronegative patients do not have these antibodies in their blood. Patients with seropositive RA share certain genetic and environmental risk factors and often have a more severe disease course. Less is known about seronegative RA.

The aim of this study was to compare the presentation of RA in seropositive and seronegative patients.

234 patients with recently diagnosed RA were included in this study. None of the patients had been treated with disease-modifying anti-rheumatic drugs (DMARDs). 15.4% of patients were seronegative. 

Swollen joint count was significantly higher in patients who were seronegative. Patients who had lower antibody levels had a significantly higher swollen joint count compared to those with higher antibody levels.

36 joints were assessed for damage and inflammation using an ultrasound-like technique called ultrasonography. Seronegative patients showed significantly more damage and inflammation in their joints and tendons than seropositive patients.

Disease activity and assessment by a physician were also significantly worse in seronegative patients. Joint tenderness, patients reported outcomes and radiography scores were similar in both groups. 

The authors concluded that seronegative patients had higher levels of inflammation than seropositive patients. 

The higher level of disease activity observed in seronegative patients was likely due to the high number of involved joints required for seronegative patients to fulfil RA classification.