Session Type: Poster Session (Sunday)
Session Time: 9:00AM-11:00AM
Background/Purpose: xClassification of axial spondyloarthritis is based on the application of either an imaging or clinical arm. Radiographic or MRI evidence of sacroiliitis can be applied for the imaging arm. However, it is well-established that reliability for detection of radiographic sacroiliitis is inadequate, especially in early disease, and radiography is insensitive compared to MRI for detection of either active or structural lesions. Active lesions on MRI (MRI-A) are already included as an alternative to radiographic sacroiliitis in the imaging arm. We aimed to assess the impact of replacing radiographic sacroiliitis with MRI structural lesions (MRI-S) typical of axSpA on the number of patients classified as having axSpA in patients with undiagnosed back pain recruited to the ASAS Classification Cohort (ASAS-CC).
Methods: MRI images (STIR and T1-weighted sequences) of the sacroiliac joint (SIJ) enabling assessment of both active and structural lesions were available from 219 cases in the ASAS-CC, and these also had available clinical, laboratory, and radiographic data. Seven central readers from the ASAS-MRI group recorded MRI lesions in an eCRF that included wording of lesions defining active (MRI-A) and structural (MRI-S) lesions typical of axSpA. MRI-A was deemed to be present according to majority agreement (≥4/7) of central readers. MRI-S was deemed to be present according to the majority (majority reader MRI-S) and also according to any 2 central readers (2-reader MRI-S). We calculated the number of patients that were classified differently after replacement of radiographs by MRI-S for overall fulfillment of the ASAS criteria and for the imaging arm.
Results: In total,124 (56.6%) fulfilled the ASAS axSpA criteria based on local reading of radiographic sacroiliitis and central reading of MRI-A. This changed to 126 (57.5%) and 120 (54.8%) patients after replacement of radiographic sacroiliitis by 2-reader and majority reader MRI-S, respectively (Table). 9 (4.1%) and 4 (1.8%) of patients who were not classified as axSpA were then re-classified as axSpA after substitution with 2-reader and majority reader MRI-S, respectively. Conversely, 7 (3.2%) and 8 (3.7%) were re-classified as not axSpA after substitution by 2-reader and majority reader MRI-S, respectively. When fulfillment of the imaging arm was required (irrespective of the clinical arm), the number of patients reclassified from not axSpA to axSpA was 18 (8.2%) by 2-reader MRI-S and 8 (3.7%) by majority reader MRI-S, while 8 (3.7%) and 11 (5.0%) were reclassified from axSpA to not axSpA, after substitution of radiographic sacroiliitis with 2-reader and majority reader MRI-S, respectively.
Conclusion: The number of patients classified as having axSpA does not change substantially when MRI-S replaces radiographic sacroiliitis. However, it is unclear to what degree MRI structural lesions could have affected the final diagnostic ascertainment, the gold standard for assessment of the performance of the ASAS criteria.
To cite this abstract in AMA style:Maksymowych W, Machado P, Lambert R, Baraliakos X, Østergaard M, Sieper J, Wichuk S, Poddubnyy D, Rudwaleit M, van der Heijde D, Landewé R, Paschke J, Juhl Pedersen S, Weber U. Replacement of Radiographic Sacroilitis by MRI Structural Lesions: What Is the Impact on Classification of Axial Spondyloarthritis in the ASAS Classification Cohort? [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/replacement-of-radiographic-sacroilitis-by-mri-structural-lesions-what-is-the-impact-on-classification-of-axial-spondyloarthritis-in-the-asas-classification-cohort/. Accessed December 7, 2019.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/replacement-of-radiographic-sacroilitis-by-mri-structural-lesions-what-is-the-impact-on-classification-of-axial-spondyloarthritis-in-the-asas-classification-cohort/