Background The natural history (with regard to the structural damage of the Sacroiliac Joints) (SIJ) of axial radiographic (r) and non-radiographic (nr) axial spondyloarthritis (SpA) is not well known.
Objectives To evaluate the 2 years SIJ radiological structural changes in early axial r- versus nr-axial SpA according to different definitions.
Methods Patients: inflammatory back pain of less than 3 years duration suggestive of axial SpA according to the treating rheumatologist (DESIR cohort). Outcome measures: Pelvic X-rays collected both at baseline and at the 2 year follow up visit were stored after anonymizing and blinding of the time collection. The radiographs were read centrally by two different readers of well calibrated central readers blinded for clinical, laboratory and other imaging data. In case of disagreement regarding the presence/absence of either sacroiliitis according to the modified New York (mNY) cri teria or change of at least one grade in one SIJ, images were adjudicated by an experienced radiologist or rheumatologist. A score from 0 (normal) to 4 (fusion) was given to each SIJ (left and right). Analysis: Several outcome measures were used: a) changes (from nr to r or from r to nr) in the SIJ status according to the mNY criteria (e.g. r in case of at least a unilateral garde 3 or bilateral grade 2), b) changes in the 0-8 total SIJ (left + right) score c) progression/improvement defined by a change of at least one grade (≥+1/≤-1) in either the left or right SIJ, d) Progression defined by a change of at least one grade in either the left or right SIJ AND a 2 year value of at least 2 in this joint with a progression of at least one grade.
Results The table summarizes the changes observed in the 449 evaluated patients (age: 34±9 + years old, male: 47%, HLA B27 positive: 61%) according to the baseline radiographic status
Conclusions These data suggest that in early SpA a) the structural progression does exist but is quite small and only observed in a small number of patients, b) there is a relatively high rate of improvement indicating that it is difficult to assess the true progression rate c) the total SIJ score and/or the progression defined by a change of at least one grade are the most sensitive, d) such rate of progression is higher in the sub-group of patients fulfilling the mNY criteria at baseline.
Acknowledgements DESIR is financially supported by an unrestricted grant from PFIZER France and the French Society of Rheumatology
Disclosure of Interest None declared