Background The interpretation of findings on MRI and radiographs of the sacroiliac joints (MRI-SI and X-SI respectively) is known to vary amongst radiologists and trained readers as recently shown in the DESIR-cohort in France1. Since imaging is used in the ASAS axial spondyloarthritis (axSpA) criteria for the classification of patients, different findings can result in a different SpA classification.
Objectives To objectify if classification (ASAS axSpA criteria) of patients (pts) in the SPACE-cohort differed based on evaluation of MRI-SI and X-SI by radiologists (local evaluation) and two blinded readers (central reading).
Methods The SpondyloArthritis Caught Early (SPACE)-cohort includes pts with chronic back pain (≥3 months, ≤2 years, onset <45 years) visiting the rheumatology outpatient clinics of five participating centres in the Netherlands, Norway and Italy. Local radiologists provided information on bone marrow oedema compatible with sacroiliitis and signs of radiographic sacroiliitis compatible with axSpA without formal scoring. MRI-SI were scored by the central readers according to the ASAS definition and X-SI were scored according to the mNY criteria. In case of disagreement, an experienced reader served as adjudicator. MRI-SI and X-SI were considered positive if 2/3 readers agreed. Pts were classified according to the ASAS axSpA criteria using the scores of local evaluation and again using the scores of central reading.
Results In total, 143/395 pts (36.2%) fulfilled the ASAS axSpA criteria based on central reading and 170/395 pts (43,0%) based on local evaluation. MRI-SI was rated discordant in 34 pts (8.4%) and concordant in 27 pts (6.8%); these figures were 19 pts (4.8%) and 12 pts (3.0%) for X-SI. In 43 pts (10.9%) a different reading resulted in a different rating of presence of axSpA; 35 pts (8.9%) classified no SpA by central reading were identified as axSpA by local evaluation; 8 pts (2.0%) classified axSpA by central reading were no SpA by local evaluation. Furthermore, discrepancies were observed when interested in whether pts fulfilled the imaging and clinical arm within the ASAS axSpA criteria (see table). Twenty-two pts (5.6%) fulfilled the imaging arm by local evaluation, but fulfilled the clinical arm only based on central reading. In contrast only 4 pts (1.0%), who fulfilled only the clinical arm based on local evaluation, were reclassified into the imaging arm by central reading.
Conclusions In pts with chronic back pain 10.9% of pts were classified differently based on scores of trained central readers and local evaluation of radiologists. This was due to difference in reading in both MRI-SI and X-SI. However, in a greater proportion of pts the classification did not change even with discrepant reading because of the clinical arm of the ASAS classification criteria.
van den Berg. Ann Rheum Dis 2014.
Disclosure of Interest None declared