A comparative study on the clinical and magnetic resonance imaging features between seronegative and seropositive rheumatoid arthritis

OBJECTIVES Seronegative rheumatoid arthritis (SNRA) is less common and less known compared with seropositive rheumatoid arthritis (SPRA). The aim of this study was to characterise the clinical and magnetic resonance imaging (MRI) features of SNRA and investigate the associated factors of structural damage. METHODS We retrospectively collected newly diagnosed RA patients who had MRI data of the hands at baseline. The clinical and MRI features and treatment responses during the 12-month follow-up were compared between SNRA and SPRA. The associated factors of the erosion rate were analysed. RESULTS A total of 310 RA patients were included in this study. Compared with SPRA, SNRA had a higher level of inflammation (p-values were all <0.001), a higher incidence of low bone mineral density (p=0.009), but a lower erosion score (p<0.001) and a lower probability of interstitial lung disease (ILD) (p=0.019). The main eroded bones were different between SNRA (the scaphoid and the lunate) and SPRA (the capitate and the hamate). In the multivariate analysis, synovitis score, the levels of IL-6 and TNF-alpha, and hyperglobulinaemia were positively associated with the erosion rate of SNRA (p-values were all <0.05). During the 12-month follow-up, the treatment response between the two groups was comparable (p-values were all >0.05). CONCLUSIONS SNRA had more severe inflammation but milder erosion compared with SPRA. SNRA with severe inflammation or hyperglobulinaemia needs the same powerful therapy of SPRA to prevent erosion progression.