Baseline severity of sacroiliitis can predict acute inflammatory status of sacroiliac joint in early axial spondyloarthritis of male patients: a cross sectional study.

Background: This study compared clinical, laboratory and radiographic features of axial spondyloarthritis (axSpA) between ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nrAxSpA) of young male patients. Additionally, we sought factors which can predict the baseline inflammatory status of sacroiliac joint (SIJ) in axSpA.

Methods: We retrospectively reviewed the medical records of 322 patients who visited our hospital due to inflammatory back pain, and 159 male patients with axSpA were enrolled. Enrolled patients were divided into two groups, AS group and nrAxSpA group, and medical records, laboratory data, radiologic findings were collected and analyzed.

Results: Alternating buttock pain and CRP elevation were significantly frequent in AS patients than nrAxSpA patients (68.8% vs 41.3%, P = 0.001, 63.5% vs 37.1%, P = 0.002), and SPondyloArthritis Research Consortium of Canada (SPARCC) score of SIJ was higher in AS patients than nrAxSpA patients (14.0 vs 5.0, P < 0.0001). Baseline sacroiliitis severity, psoriasis, and CRP elevation had positive association in univariate and multivariate regression analysis for SIJ inflammatory SPARCC score.

Conclusion: AS patients were more frequently in acute inflammatory state than nrAxSpA patients according to laboratory and MRI finding. Baseline sacroiliitis grade was significantly associated with baseline inflammatory SPARCC score of SIJ. AS patients might need more intense initial treatment to resolve active inflammatory lesion of SIJ and prevent further radiologic progression.