Classification of axial SpA based on positive imaging (radiographs and/or MRI of the sacroiliac joints) by local rheumatologists or radiologists versus central trained readers in the DESIR cohort

Objective Investigating changes in patient classification (ASAS (Assessment of SpondyloArthritis international Society) axSpA criteria) based on evaluation of images of the sacro-iliac joints (MRI-SI and X-SI) by local and central readers. Methods The DESIR cohort included patients with inflammatory back pain (IBP; >= 3 months, but <3 years), suggestive of axSpA. Local radiologists/rheumatologists (local-reading) and two central readers (central-reading) evaluated baseline images. Agreement regarding positive MRI (pos-MRI) between central readers and between local-reading and central-reading was calculated (kappa s). Number of patients classified differently (ASAS criteria) by using local-reading instead of central-reading was calculated. Results Inter-reader agreement between the two central readers and between local-reading and central-reading was substantial (kappa=0.73 and kappa=0.70, respectively). In 89/663 MRI-Sls (13.4%) local-reading and central-reading disagreed; 38/223 patients (17.0%) with pos-MRI (localreading) were negative by central-reading; 51/440 patients (11.6%) with neg-MRI (local-reading) were positive by central-reading. In 163/582 patients eligible for applying ASAS criteria (28.0%), local-reading and central-reading disagreed on positive imaging (MRI-SI and/or X-SI; kappa=0.68). In 46/582 patients (7.9%) a different evaluation resulted in a different classification; 18/582 patients (3.1%) classified no-SpA (central-reading) were axSpA by local-reading; 28/582 patients (4.8%) classified axSpA (central-reading) were no-SpA by local-reading. Among axSpA patients (central-reading), 16/419 patients (3.8%) fulfilling imaging-arm by central-reading fulfilled clinical-arm by local-reading; 29/419 patients (6.9%) fulfilling clinical-arm by central-reading fulfilled also imaging-arm by local-reading. Conclusions In patients with recent onset IBP, trained readers and local rheumatologists/radiologists agree well on recognising a pos-MRI. While disagreeing in 28% of the patients on positive imaging (MRI-SI and/or X-SI), classification of only 7.9% of the patients changed based on a different evaluation of images, showing the ASAS axSpA criteria's robustness.