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SAT0278 How useful is imaging of the SI-joints (MRI and/or X-ray) in patients with possible spondyloarthritis in the diagnostic work-up?


Background In daily practice, the diagnostic work-up of patients with possible axial spondyloarthritis (SpA) starts with clinical and laboratory data. In many patients MRI and/or X-rays of the SI-joints (MRI-SIJ and X-SIJ) are performed to be able to diagnose patients with confidence.

Objectives To investigate what the contribution is of imaging (MRI-SIJ and X-SIJ) in making a final diagnosis with confidence.

Methods All patients with chronic back pain (≥3 months, ≤2 years, onset <45 years) in the SPondyloArthritis Caught Early (SPACE)-cohort in our clinic underwent a diagnostic work-up according to a fixed protocol. First, medical history, physical examination and laboratory assessments, including HLA-B27 typing, were performed. Based on this information, an experienced rheumatologist diagnosed all patients as either SpA or no-SpA with a level of confidence (scale 0 (not confident at all) to 10 (very confident)). Second, imaging (MRI-SIJ and X-SIJ) was performed and a diagnosis was recorded by the same rheumatologist with a new level of confidence. For the analyses, cut-off values of ≤5 (not confident) and ≥6 (confident) were used.

Results In 52/157 of the patients (33.1%), the rheumatologist was confident about the diagnosis, either SpA (n=31) or no-SpA (n=21), based on clinical and laboratory data only. Imaging was positive in 32/157 patients (20.4%). In 3/52 patients (5.7%) the rheumatologist was confident about the diagnosis no-SpA, but revised the diagnosis into confident SpA after imaging. In 9/52 patients (17.3%), the rheumatologist was confident about the diagnosis based on clinical data only, but was not confident anymore after receiving negative imaging. In 105/157 of the patients (66.9%), the rheumatologist was not confident about the diagnosis. After performing imaging, the rheumatologist was confident about the diagnosis in 73/105 patients: SpA in 21 (20.0%) patients and no-SpA in 52 (49.5%) patients. In the remaining 32 (30.5%) patients imaging did not change confidence, nor diagnosis (table).

Conclusions Imaging (MRI-SIJ and/or X-SIJ) is useful for the rheumatologist in the large majority of patients with possible axial SpA, except for the patients in which the rheumatologist is confident about the diagnosis of SpA before imaging.

Disclosure of Interest None Declared

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