RADIOGRAPHIC PROGRESSION FROM NONRADIOGRAPHIC TO RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS: RESULTS FROM A 5-YEAR MULTICOUNTRY PROSPECTIVE OBSERVATIONAL STUDY
Authors: D. Poddubnyy et al.
Patients are classified as radiographic or non-radiographic axial Spondyloarthritis (r-axSpA, nr-axSpA) according to the presence of absence of sacroiliitis on conventional X-ray. The estimations of how many newly diagnosed patients with nr-axSpA will progress to r-axSpA vary widely. This large prospective real-world multicenter study evaluated progression from nr-axSpA to r-axSpA over 5 years. 1612 patients were either classified as nr-axSpA (35%) or r-axSpA (65%). In 246 patients with nr-axSpA follow up radiographs were available. Progression to r-axSpA was observed in 40 patients (16%), within a mean time of 2.4 years. Predictors for progression were male gender, good response to NSAIDs, fulfilment of the imaging arm of diagnostic criteria and HLA-B27 positivity.
There is still uncertainty on whether nr-axSpA is an early presentation of r-axSpA or rather a distinct entity. This large study showed that within 5 years only a minority of patients with nr-axSpA progress to r-axSpA. In particular male patients and patients with good response to NSAIDs have a higher probability to switch to r-axSpA. This may contribute to the male predominance in ankylosing spondylitis as opposed to a more equal sex distribution in nr-axSpA.