Background According to the new ASAS criteria, the initial imaging modality for the diagnostics of sacroiliitis remains the conventional radiographic examination, based on the modNY criteria for AS [1,3]. MRI of sacroiliac joints is a second-line method of choice, conducted when the radiographs does not meet the modNY criteria [1,2].
Objectives The study was aimed at a comparative evaluation of SIJ radiographs and MRI in patients with a clinical diagnosis of SpA according to the current ASAS criteria.
Methods SIJs radiographs and MRI were conducted in 84 consecutive patients, including 33 males and 51 females, aged 19-55 yrs (mean age: 37 yrs). The patients were referred by a senior rheumatologist, with symptoms of the chronic back pain. The ASAS 2009 criteria for axial SpA were applied [1,2,3].
Results On radiographs, inflammatory lesions of SIJs were found in 53 out of the evaluated 168 joints (32%).
In MRI, bone marrow edema (BME) fulfilling ASAS sacroiliitis criteria was found in 48 out of the evaluated 168 joints (29%). BME was accompanied by synovitis in 18 joints (11%), enthesitis in 4 joints (2%), capsulitis in 2 joints (1%), erosions in 24 joints (14%), sclerosis in 85 joints (51%) and fatty transformation of bone marrow in 97 joints (58%).
Among 11 patients with sacroiliitis by radiographs according to modNY criteria, 6 were confirmed with inflammatory lesions in MRI (55%, 6/11), further 5 were not confirmed with sacroiliitis features in MRI (45%)(κ =0.1, the agreement of radiographs and MRI was 63%). Among 72 patients without sacroiliitis features by radiographs according to modNY criteria (in i.e. preradiographic stage of the disease), MRI confirmed the lack of inflammatory lesions in 46 cases (64%), in further 26 inflammatory lesions in SIJs were found (36%).
Conclusions Our research confirmed MRI to visualize early inflammatory lesions [4,5].
The agreement of radiographic and MR imaging of sacroiliitis was documented in only 63% of cases, including 46 patients in whom both modalities ruled out the presence of inflammatory lesions, and only 6 in whom they both confirmed sacroiliitis features.
The comparable number of true positive and negative results by radiographs in patients meeting the modNY criteria questions the validity of taking radiographs in SpA with the purpose of diagnosing inflammation.
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Disclosure of Interest None declared
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