Background In the diagnostic work-up of spondyloarthritis (SpA), imaging of the SI-joints by MRI (MRI-SIJ) is an important step. One study showed that in HLA-B27+ patients and male patients it might be useful to repeat an MRI after one or two years1. It is not known if repeating an MRI after a shorter period than 1 year is useful.
Objectives To investigate whether it is useful to repeat an MRI after 3 months in the diagnostic process for SpA.
Methods Patients with chronic back pain (n=157) (≥3 months, ≤2 years, onset <45 years) included in the SPondyloArthritis Caught Early (SPACE)-cohort in the Leiden University Medical Center (LUMC) underwent an MRI-SIJ during baseline visit. Patients with SpA and possible SpA (n=90) underwent a follow-up visit after 3 months, again including MRI-SIJ. MRI-SIJs were scored by 3 independent readers “positive” or “negative” according to the ASAS definition2, blinded for the time-sequence. If 2/3 reads were positive, the MRI-SIJ was marked as positive.
Univariate and multivariate regression analyses were performed to investigate which variables (IBP, elevated CRP, MRI-status at baseline, gender, HLA-B27-status and age at onset) could predict a positive MRI-SIJ at 3 months.
Results Only patients with complete MRI data are included in this analysis (n=90). In the univariate analysis, a positive MRI-SIJ at baseline was the strongest predictor of a positive MRI-SIJ over time (OR 49.5, 95% CI 11.9-206.7, p<0.001). Regardless MRI-status, gender and HLA-B27-status (OR 7.7, 95% CI 2.6-23.1, p<0.001 and OR 2.6, 95% CI 0.9-7.0, p=0.07, respectively) are strong predictors of a positive MRI over time. The latter 2 variables were used in a multivariate model. Groups were made based on this model (table). In the majority of the patients (90%), MRI-status, either positive (n=15) or negative (n=66), did not change over time. Of the patients with a negative MRI-SIJ at baseline, 5 (7%) developed a positive MRI-SIJ after 3 months and in 4 out of 19 patients (21.1%) lesions on MRI-SIJ disappeared over time. Two out of 5 patients in whom MRI was positive for the first time at follow-up fulfilled the ASAS axial SpA criteria only at follow-up.
Conclusions We confirmed that a positive MRI-SIJ at baseline is a very strong predictor for a positive MRI-SIJ after 3 months. In patients with a negative MRI-SIJ at baseline, male gender and HLA-B27 are predictive of a later positive MRI-SIJ. In this group of patients with short symptom duration, variation in MRI-SIJ positivity occurred in 10% of the patients over a very short period of only 3 months. A positive change of MRI-SIJ has led to a different classification in 2.2% (n=2) of the patients. More data are needed to decide if it is necessary to repeat MRI, and if so, with what time interval.
Van Onna M. ARD 2011;70:1981-5.
Rudwaleit M. ARD 2009;68:1520-7
Disclosure of Interest None Declared