T1w MRI was superior to radiography in the detection of structural lesion of the SI joints in patients with axSpA. Future studies should focus on finding an agreement on the definition of MRI-T1 positivity.

VIBE detected erosions in the SIJs with higher sensitivity without a loss of specificity and superior reliability compared with a standard T1-weighted sequence. Its value for the diagnosis of axSpA has still to be determined.

ObjectiveTo assess the diagnostic accuracy of radiography (X-ray, XR), CT and MRI of the sacroiliac joints for diagnosis of axial spondyloarthritis (axSpA).Methods163 patients (89 with axSpA; 74 with degenerative conditions) underwent XR, CT and MR. Three blinded experts categorised the imaging findings into axSpA, other diseases or normal in five separate reading rounds (XR, CT, MR, XR +MR, CT +MR). The clinical diagnosis served as reference standard. Sensitivity and specificity for axSpA and inter-rater reliability were compared.ResultsXR showed lower sensitivity (66.3%) than MR (82.0%) and CT (76.4%) and also an inferior specificity of 67.6% vs 86.5% (MR) and 97.3% (CT). XR +MR was similar to MR alone (sensitivity 77.5 %/specificity 87.8%) while CT+MR was superior (75.3 %/97.3%). CT had the best inter-rater reliability (kappa=0.875), followed by MR (0.665) and XR (0.517). XR +MR was similar (0.662) and CT+MR (0.732) superior to MR alone.ConclusionsXR had inferior diagnostic accuracy and inter-rater reliability compared with cross-sectional imaging. MR alone was similar in diagnostic performance to XR+MR. CT had the best accuracy, strengthening the importance of structural lesions for the differential diagnosis in axSpA.

Objective.To compare proton density–weighted short-tau inversion recovery (PD-STIR) and T2-weighted fat-suppressed turbo spin echo (T2-FS) sequences for detecting osteitis lesions of the sacroiliac joints (SIJ) in patients with chronic low back pain (CLBP).Methods.This prospective study included 110 patients with CLBP and suspected spondyloarthritis and 18 healthy controls. All 128 participants (age range: 19–57 yrs) underwent 3.0 Tesla magnetic resonance imaging (MRI) of the SIJ including PD-STIR and T2-FS. Two readers independently scored PD-STIR and T2-FS images for osteitis in separate sessions. Sum scores and signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Images were further analyzed as to whether they fulfilled the Assessment of SpondyloArthritis international Society (ASAS) criterion of a positive MRI (MRI+). Interreader agreement was calculated using intraclass correlation coefficients.Results.Average osteitis sum scores were higher for T2-FS images (mean sum score of 4.10 in T2-FS vs 2.55 in PD-STIR, p = 0.017). Mean SNR was 16.54 for PD-STIR and 37.30 for T2-FS (p = 0.0289). Mean CNR was 4.14 for PD-STIR and 20.20 for T2-FS (p = 0.0212). For both readers, the ASAS MRI+ definition was more often fulfilled by T2-FS than by PD-STIR images, resulting in more patients being classified as having axial spondyloarthritis (axSpA): 68 patients using T2-FS versus 58 patients using PD-STIR. Interreader intraclass correlation coefficients were very good for both PD-STIR (0.91) and T2-FS (0.86).Conclusion.T2-FS sequences improve image quality and hence the detection of osteitis compared to the PD-STIR sequence. More patients were classified as axSpA based on a positive MRI by T2-FS.

ObjectivesTo propose a data-driven definition for structural changes of sacroiliac (SI) joints in the context of axial spondyloarthritis (axSpA) imaging on a large collective of CT datasets.Methods546 individuals (102 axSpA, 80 non-axSpA low back pain and 364 controls without back pain) with SI joint CTs were evaluated for erosions, sclerosis and ankylosis using a structured scoring system. Lesion frequencies and spatial distribution were compared between groups. Diagnostic performance (sensitivity (SE), specificity (SP), positive predictive values, negative predictive values and positive and negative likelihood ratios) was calculated for different combinations of imaging findings. Clinical diagnosis served as standard of reference.ResultsAnkylosis and/or erosions of the middle and dorsal joint portions yielded the best diagnostic performance with SE 67.6% and SP 96.3%. Inclusion of ventral erosions and sclerosis resulted in lower diagnostic performance with SE 71.2%/SP 92.5% and SE 70.6%/SP 90.0%, respectively.ConclusionsSclerosis and ventrally located erosions of SI joints have lower specificity on CT of the SI joint in the context of axSpA imaging. Ankylosis and/or erosions of the middle and dorsal joint portions show a strong diagnostic performance and are appropriate markers of a positive SI joint by CT.

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Background The value of magnetic resonance imaging (MRI) in the detection of erosions on the sacroiliac joints (SI-joints) is controversial. Structural changes on the other hand are getting more and more into scientific focus. Objectives The aim of this study is a comparison between x-ray, low dose computed tomography (CT) and MRI. The presented data are preliminary results from the sacroiliac joint magnetic resonance imaging and computed tomography (SIMACT) study. Methods We investigated prospectively 30 patients with lower back pain and the suspicion of axSpA expressed by an experienced rheumatologist. All patients underwent a low dose CT (Somatom Definition Flash, Siemens, Germany) and an MRI (3.0T Magnetom Skyra, Siemens, Germany) of the SI-joints. Imaging data were compared with X-ray of the pelvis. The MRI protocol contained these sequences: T1-weighted spine echo (T1-SE), short tau inversion recovery (STIR), T1-weighted 3D volumetric interpolated breath hold examination (VIBE) high resolution sequence, all in paracoronal orientation. The grade of the disease was scored in X-ray according to the modified New York criteria and the erosions were counted by quadrant by a blinded reader. The final diagnosis made by the rheumatologist was also used for comparison. Results CT and T1-SE showed no significant differences in detecting erosions. 3D-VIBE found significantly more erosions in patients with axSpA compared to CT and T1-SE. (n=22; CT 178 erosions, T1 163, VIBE 421; average CT 5.9, T1 5.4, VIBE 14.0; p<0.001). In other diagnosis (osteoarthritis N=4, triangular hyperostosis N=3, others N=1) there were no significant differences among imaging modalities. The erosion count in 3D-VIBE correlated with the grade of sacroiliitis in X-ray (r=0.123, p=0.007). Conclusions High-resolution 3D MR sequences like 3D-VIBE are more suitable in detecting erosions on the SI-joints than conventional MRI (T1-SE) and even low dose CT. They are therefore a reasonable supplement to any MRI protocol and may improve the ability of MRI for diagnosis both in early and advanced SpA. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.2145

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