Background Inflammatory lesions of the spine are not included in the ASAS definition of a positive MRI for fulfilment of the ASAS axial spondyloarthritis (axSpA) criteria1. However, inflammatory lesions in the spine on MRI (MRI-spine) may occur in the absence of affected sacroiliac joints (SIJ).
Objectives To determine the prevalence of inflammatory lesions on MRI-spine and to investigate if axSpA patients (pts) with inflammatory lesions in the spine only exist.
Methods The SPondyloArthritis Caught Early (SPACE)-cohort includes pts with chronic back pain (≥3 months, ≤2 years, onset <45 years) recruited from 5 participating centres. All pts underwent MRI of the SIJ (MRI-SI) and MRI-spine scored by 3 well-calibrated readers independently. MRIs-SI were scored according to the ASAS definition1 (≥1 lesion on ≥2 consecutive slices or >1 lesion on 1 slice). Inflammatory lesions on MRI-spine suggestive of spondylitis were scored when visible on ≥2 consecutive slices and according to the ASAS consensus definition2 (≥3 lesions on ≥2 consecutive slices). Lesions were considered present if 2/3 readers agreed.
Results All pts with MRI-spine (n=306) were included to determine the prevalence of BME lesions in pts grouped according to the ASAS axSpA criteria (radiographic, non-radiographic (imaging & clinical arm), no-SpA and possible SpA (table 1). 292 pts had both MRI-SI and MRI-spine. There were 51 pts with a positive MRI-spine, of which 30 pts (58.8%) had a negative MRI-SI. Nine of these 30 fulfil the ASAS axSpA criteria via the clinical-arm. Of the remaining 21 pts, 3 pts had no SpA features at all, 7 had 1 SpA feature, 8 had 2 SpA features, 1 had 3 SpA features and 2 had 4 SpA features. Only the sole patient with 4 SpA features had a probability (calculated from the Likelihood Ratio (LR) product) >80%. When using the ASAS consensus definition of a positive MRI-spine in post-test probability calculations, another 6 pts would reach a probability ≥80% of having axSpA.
Conclusions A cut-off of ≥3 BME lesions discriminates well between pts with and without axSpA. A positive MRI-spine can be present in pts without inflammation on MRI-SI. MRI-spine might have additional value to MRI-SI in a group of pts with a certain level of suspicion of axSpA.
Rudwaleit ARD 2009;68:1520-7
Hermann ARD 2012;71:1278-88
Disclosure of Interest None Declared