Patients with non-radiographic axial spondyloarthritis differ from patients with ankylosing spondylitis in several aspects

Abstract

Objective:

Patients with axial spondyloarthritis (SpA) who have structural changes in the sacroiliac joints and/or the spine have been classified as ankylosing spondylitis (AS) while those without such changes are now named non-radiographic axial SpA (nr-axSpA). The differentiating features are incompletely understood.

Methods:

Data of 100 consecutive patients with axial SpA not treated with TNF antagonists were compared clinically and with laboratory parameters, spinal x-rays and MRI of the spine. Standardized clinical assessment tools were used to assess health status.

Results:

AS was diagnosed in 56 and nr-axSpA in 44 patients. Signs of inflammation were significantly higher in patients with AS than in patients with nr-axSpA, with a median CRP of 8.0 in AS patients compared with 3.8 in nr-axSpA, median ASDAS (2.2 vs. 2.8), median amount of spinal inflammatory lesions on MRI (2.0 vs. 0.0). Significant differences between these two groups were seen in gender (76.8% vs. 31.8% male). Clinical variables did not differ between patients with AS and nr-axSpA (BASDAI, BASFI, ASQoL, SF-36).

Conclusion:

Patients with nr-axSpA are characterized by the low proportion of males and the low burden of inflammation compared to AS patients. While both groups do not differ regarding health status, disease activity and physical function, they do differ in signs of inflammation – all were higher in patients with AS. Since many patients with nr-axSpA had not developed structural changes after years of symptoms, we propose that those patients should not be regarded as pre-radiographic AS but rather as nr-axSpA. © 2012 by the American College of Rheumatology