Comparison of patients with ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA) from a single rheumatology clinic in New Delhi

AimComparison of ankylosing spondylitis (AS) with non-radiographic axial spondyloarthritis (nr-axSpA) classified with the recent ASsessment of spondyloArthritis International Society (ASAS) criteria. Patients & MethodsThis study included 288 patients clinically diagnosed as having spondyloarthritis (SpA) where a satisfactory radiograph of sacroiliac (S-I) joints was available. The AS and the nr-axSpA groups were compared for the various SpA-related variables. ResultsOf 288 axSpA patients, there were 187 with AS. Of the remaining 101 patients without radiographic sacroiliitis, S-I joint magnetic resonance imaging (MRI) was available in 72; 54 of them showed active sacroiliitis thus classified as nr-axSpA according to the ASAS criteria. The remaining 18 patients with normal MRI and the other 29 patients without MRI of the S-I joints (total 47 patients), were classified as nr-axSpA using the clinical arm' of the ASAS criteria. On comparing the 187 AS with 101 patients in the nr-axSpA group, the AS group showed significantly more males, longer disease duration, more axial symptoms at disease onset, higher Bath Ankylosing Spondylitis Metrology Index and more syndesmophytes. Biologicals were offered significantly more often to the AS group but methotrexate as monotherapy or in combination with other disease-modifying anti-rheumatic drugs was offered more often in nr-axSpA group. There was no statistically significant difference between AS and nr-axSpA in other SpA parameters. ConclusionThe differences brought out between AS and nr-axSpA groups show that they may not be the same disease. A prospective long-term follow-up of large cohorts may help in clarifying if nr-axSpA is simply an early stage in the spectrum of SpA evolving into AS over time or is there inherent difference between them.