Ankylosing spondylitis and non-radiographic axial spondyloarthritis: Two stages of disease?

Aim. To compare the clinical manifestations of ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nrAxSpA). Subjects and methods. A Moscow early spondyloarthritis cohort has now included 132 patients with axial spondyloarthritis, of whom 69 patients who have been followed up at least 12 months are to be involved in a preliminary analysis. The mean age at the time of inclusion in the study was 28.1±5.5 years; the mean disease duration was 24.7±15.8 months; 63 (91.3%) patients were HLA-B27 positive; 41 and 28 included patients were diagnosed with AS and nrAxSpA, respectively. Results. Men were significantly more in the AS group than in the nrAxSpA group (58.5 and 32.1%, respectively; p=0.05). The patients of the two groups did not differ in main clinical parameters (the presence of arthritis and enthesitis), disease activity (BASDAI, ASDAS-CRP) and functional status (BASFI). All indicators of inflammatory activity decreased nearly 2-fold in both groups after 12 months of follow up. In 7 (25%) patients with nrAxSpA, radiologically detectable sacroiliitis (SI) developed over 12 months and the diagnosis of AS was verified. Among them, 2 (28.5%) patients had initially active SI detected by magnetic resonance imaging (MRI); 4 (57.1%) had chronic SI, and 1 (14.4%) had no pathological MRI changes. Conclusion. Due to the fact that the clinical manifestations of AS and nrAxSpA are comparable, it can be assumed that the latter is an early stage of AS.