P175 Diagnostic utility and economic impact of a sequential magnetic resonance imaging protocol in axial spondyloarthritis: a retrospective cohort study

Background/Aims Diagnosis of axial spondyloarthritis is a diagnosis based on both clinical history and characteristic radiographic and magnetic resonance imaging (MRI) findings. MRI is increasingly used to diagnose non-radiographic axSpA. Current BRITSpA guidance recommends MRI scanning both sacroiliac joints (SIJ) and whole spine to identify inflammatory lesions as defined by the ASAS MRI working group. However, the main question is whether all patients need both MRI of SIJ and spine to achieve a diagnosis of axSpA. Here, we propose a sequential MRI SIJ followed by MRI spine only for those patients who do not have inflammatory lesions on MRI SIJ, to optimise MRI use and save resources. Methods This is an observational retrospective cohort study conducted in our tertiary centre specialist axial spondyloarthritis clinic. We included only patients with a diagnosis of axial spondyloarthritis with both MRI spine and SIJ, who were referred between January 2024 to November 2024 to our tertiary service. Radiology reports were then reviewed by clinicians and determined if the MRI SIJ imaging alone was sufficient for the diagnosis, or if the MRI whole spine imaging was necessary to achieve a diagnosis of axSpA. Cost minimization analysis was performed using costs taken from the NHS National Cost Collection Data Publication 2023/24. Logistical regression was performed to identify potential clinical characteristics that may predict need for both SIJ and spine MRI for diagnosis. Results 62 patients were included in this analysis. 51 patients (82.3%) had changes on MRI SIJ alone that were diagnostic for active inflammatory lesions compatible with a diagnosis of axSpA and 11 patients (17.7%) needed to have further spinal MRI to identify inflammatory lesions. A cost minimisation analysis of utilising a sequential scanning protocol where patients would initially have an MRI SIJ that would be reviewed by a clinician to determine whether further MRI spine was needed identified potential cost savings of £11,118 and 34.0 hours of active scanning time. Logistical regression identified that there was a trend that patients with IBD were at greater odds ratio of 3.80 (95% CI 0.537- 26.952, p = 0.181) of needing a spinal MRI in addition to SIJ MRI to achieve an axSpA diagnosis. A history of HLA-B27 positivity, psoriasis, uveitis was not associated with a greater likelihood of needing an MRI spine in addition to MRI SIJs to achieve axSpA diagnosis. Conclusion Our analysis has demonstrated that there are potential significant resource savings from a cost and MRI-scanning time perspective by the implementation of a sequential MRI scanning protocol in patients with a high clinical suspicion of axSpA. Additionally, we have identified IBD as a clinical variable that may potentially be predict need for further MRI spine imaging in addition to MRI SIJs imaging. Disclosure J. Yuan-Doré: None. S. Kumar: None. L. Kostanjsek: None. S. Tahir: None. S. Bamford: None. W. Tilden: None. H. Tahir: None.