Background/Purpose

The diagnosis of ankylosing spondylitis (AS) is based on disease specific bone damage seen on plain radiography of the pelvis. Recent developments in magnetic resonance imaging (MRI) techniques have demonstrated that active inflammation in the sacroiliac joints (SIJ) and/or spine is detectable by MRI and might even be visible before the appearance of chronic changes on plain radiography. However, the current literature discussing the actual diagnostic properties of MRI in early spondyloarthritis (SpA)/non-radiographic axial SpA remains controversial and its prognostic value regarding the future development of AS has yet to be determined.

Methods

In this cross-sectional study, we recruited 70 patients with chronic inflammatory back pain (mean disease duration of 5 years) and high disease activity (BASDAI≥4) who had to be either HLA-B27 positive with ≥1 SpA-feature or HLA-B27 negative with ≥2 SpA-features. All patients underwent MRI of the SIJ and 50 patients underwent additional MRI of the spine on baseline. A positive MRI was defined by the presence of either BMO and/or osteitis, a negative MRI by the absence of both. Patients with a negative baseline MRI were asked to undergo a second MRI after 6 months. Eventually, 29 out of 49 patients with a negative baseline MRI SIJ and 22 out of 47 patients with a negative baseline MRI spine were willing and eligible to undergo the second MRI. Additionally, all patients were tested for CRP and ESR levels, X-rays of the pelvis were made and several patient features were recorded. Correlation analysis was performed between the different collected variables.

Results

At baseline, only 21 of the 70 patients (30%) showed signs of inflammation on MRI: 18 had sacroiliitis, 2 had spinal involvement and one patient had both. In total, only 4 patients presented with inflammation of the spine at baseline and six months, of which 2 also suffered from sacroiliitis. Comparison of the two consecutive MRIs revealed that, in two patients, the inflammatory process spread from the SIJ to the spine or the other way around. Only one patient with a negative baseline MRI SIJ developed apparent sacroiliitis over time. Furthermore, three patient characteristics were significantly associated with a positive MRI outcome at any point in time: raised CRP-level (p=0.032), family history of uveitis (p=0.028) and the number of swollen joints (SJC, p=0.023). We also observed a slight difference regarding HLA-B27-status and medical history of uveitis, in favor of the positive MRI-group.

Conclusion

Only a small number of patients with clinically suspected non-radiographic axial SpA showed signs of inflammation on MRI SIJ and/or spine, questioning the sensitivity and with this the value of this new imaging tool in early SpA. Even though, some patient characteristics seem to be positively associated with MRI outcome, defining the right place of MRI in the diagnosis of early SpA remains difficult. The diagnostic properties of MRI in this particular patient group should be weighted carefully because patients with a negative MRI might also have severe complaints.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/mri-is-often-negative-in-clinically-suspected-non-radiographic-axial-spondyloarthritis/