The correlations between C-reactive protein and MRI-detected inflammation in patients with axial spondyloarthritis: a systematic review and meta-analysis

Background C-reactive protein (CRP) and magnetic resonance imaging (MRI) are widely used to monitor inflammation in patients with axial spondyloarthritis (axSpA), but the relationship between CRP and MRI-detected inflammation is incompletely understood. The present study was undertaken to assess correlations between CRP and MRI-detected inflammation in axSpA. Materials and methods A systematic literature search was performed (Medline, Embase, and Cochrane Library) to identify relevant studies concerning CRP and MRI-detected inflammation in axSpA patients. The MRI-detected inflammation was evaluated by MRI-based disease activity score (DAS). The correlation between CRP and MRI-based DAS was integrated by random-effect models. Results Eighteen studies reported a total of 1392 axSpA patients which were included in this meta-analysis. CRP was significantly associated with spinal MR DAS ( r =0.226, 95%CI [0.149, 0.291], p <0.001, I 2 =23%). We also found a moderate correlation between CRP change and spinal MR DAS change ( r [ASspiMRI-a]=0.354, 95%CI [0.282, 0.422], p <0.001, I 2 =48%; r [SPARCC]=0.544, 95%CI [0.345, 0.701], p <0.001, I 2 =19%). CRP at baseline was negatively associated with improvement in spinal MR DAS ( r = − 0.327, 95%CI [−0.397, −0.264], p <0.001, I 2 =0%). However, no significant association was found between CRP and sacroiliac joint (SIJ) MR DAS. Conclusions In axSpA patients, CRP is associated with MRI-detected inflammation in the spine but not in SIJ. We speculate that CRP could be a reasonable index to reflect spinal inflammation. Therefore, we suggest it is not essential to repeat spinal MRI in a short term, while SIJ MRI may be necessary to provide additional information on inflammation. Key Points • CRP is associated with MRI-detected inflammation in the spine but not in sacroiliac joints . • CRP at baseline was negatively associated with improvement in spinal MR DAS . • It was not essential to repeat spinal MRI frequently, while SIJ MRI may be necessary to provide additional information on inflammation .