Background/Purpose:  Antero-posterior (A-P) view radiograph of pelvis was usually used to diagnose sacroiliitis. Magnetic resonance imaging (MRI) can detect lesions in early disease before lesions can be seen on radiography. The oblique views radiographs of pelvis can provide additional information that makes it closer to the findings of MRI than A-P view radiograph. In this study, we attempted to record lesions of sacroiliac joint (SIJ) seen on A-P view and oblique views radiographs and MRI in patients with axial Spondyloarthritis (SpA), and to analyze whether oblique views are better than A-P view radiographs in assessing sacroiliitis.

Methods:  All patients fulfilled the 2009 ASAS classification criteria for axial SpA. Three readers blinded (two radiologists and one rheumatologist) investigated the A-P view and oblique views radiographs and MR images from 182 patients with axial SpA. The modified New York criterion was used to grade the sacroiliitis according to the lesions seen on different imaging methods. We analyzed and calculated the sensitivity, specificity, positive and negative likelihood ratio of A-P view and oblique views radiographs for diagnosing axial SpA with MRI as the gold-standard.

Results:  The total consistency was higher in oblique views and MRI than in A-P view and MRI (82.8% vs. 71.6%, p<0.01). The agreement rates were higher between oblique views and MRI than that between A-P view and MRI in the SIJs graded≤2, especially in patients with symptom duration less than 2 years (all p<0.01). But in the SIJs graded>2 and in patients with symptom duration more than 2 years, there were no differences using A-P view or oblique views to assess sacroiliitis (all p>0.05). Oblique views had high sensitivity, while A-P view had moderate sensitivity for diagnosing axial SpA in the SIJs graded≤2.

Conclusion:  We recorded and analyzed the sacroiliitis assessed by A-P view, oblique views radiographs and MRI and found that oblique views radiographs had some advantages over A-P view radiographs in assessing sacroiliitis in patients with early axial SpA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/oblique-views-radiographs-have-advantages-over-antero-posterior-view-radiographs-in-assessing-sacroiliitis-in-patients-with-early-axial-spondyloarthritis/