Utility of Magnetic Resonance Imaging in Assessing Disease Activity in Axial Spondyloarthritis Regardless of C-Reactive Protein Status

Jing Chen,1,* Yu Huang,2,3,* Hongjie Huang,4,5 Hongbing Rui,1,5 Qing Zheng1,5 1Department of Rheumatology and Immunology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian Province, 350000, People’s Republic of China; 2Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, 350005, People’s Republic of China; 3Department of Anesthesiology Fujian Children’s Hospital, Fuzhou, Fujian, 350014, People’s Republic of China; 4Department of Radiology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian Province, 350000, People’s Republic of China; 5National Regional Medical Center, Binhai Campus, The First Affiliated Hospital of Fujian Medical University, Fujian, Fuzhou, 350000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Qing Zheng, Department of Rheumatology and Immunology, The First Affiliated Hospital of Fujian Medical University, No. 20, Chazhong Road, Taijiang District, Fuzhou, Fujian Province, 350000, People’s Republic of China, Tel +86 0591 87549825, Email [email protected] Hongbing Rui, Department of Rheumatology and Immunology, The First Affiliated Hospital of Fujian Medical University, No. 20, Chazhong Road, Taijiang District, Fuzhou, Fujian Province, 350000, People’s Republic of China, Tel +86 0591 87549825, Email [email protected]: Magnetic resonance imaging (MRI) and C-reactive protein (CRP) are commonly utilized in the diagnostic and disease activity assessment of axial spondyloarthritis (axSpA). The aim of this analysis is to determine the clinical utility of MRI and CRP in assessing disease activity, particularly in patients with normal CRP levels.Methods: A retrospective evaluation was conducted on patients diagnosed with axSpA who received care at the First Affiliated Hospital of Fujian Medical University between 2022 and 2024. Comparisons were made between patients diagnosed with ankylosing spondylitis (AS) and those with non-radiographic axial spondyloarthritis (nr-axSpA) regarding clinical features, disease activity, and MRI-detected lesions.Results: A total of 719 patients diagnosed with axSpA were included. Of the 638 patients who underwent both MRI and CRP testing, 391 had normal CRP levels, and 247 had elevated CRP levels. Among patients with normal CRP levels, the frequency of active and structural lesions identified on MRI was significantly lower compared to those with elevated CRP levels (p < 0.05). Within the nr-axSpA group, the detection rate of erosive, active and structural combined lesions was significantly lower in patients with normal CRP levels compared to those with elevated CRP levels. When compared with MRI, the sensitivity and specificity of CRP in detecting active and structural lesions remained below 80%.Conclusion: In patients with normal CRP levels, MRI remains a valuable tool for evaluating disease activity in axSpA. The imaging findings indirectly indicate that erosive changes may represent an early stage in the progression from bone marrow edema to structural damage. Nr-axSpA may reflect an earlier disease stage, whereas AS represents a later stage within the axSpA spectrum.Keywords: ankylosing spondylitis, axial spondyloarthritis, magnetic resonance imaging, non-radiographic axial spondyloarthritis, spondyloarthritis, CRP, disease activity