Does spinal MRI add incremental diagnostic value to MRI of the sacroiliac joints alone in patients with non-radiographic axial spondyloarthritis?
OBJECTIVE
To assess the incremental diagnostic value of spine MRI evaluated separately from and combined with sacroiliac joint (SIJ) MRI in non-radiographic axial spondyloarthritis (nr-axSpA) compared with SIJ MRI alone.


METHODS
The study sample comprised two independent cohorts A/B of 130 consecutive patients aged ≤50 years with back pain, newly referred to two university clinics, and 20 healthy controls. Patients were classified according to clinical examination and pelvic radiographs as having nr-axSpA (n=50), ankylosing spondylitis (n=33), or non-specific back pain (n=47). Four readers assessed SIJ and spine MRI separately 6 months apart, and 1-12 months later both scans simultaneously using standardised modules. Readers recorded presence/absence of SpA and their level of confidence in this conclusion on a 0-10 scale (0=definitely not; 10=definite). We analysed differences between SIJ MRI versus spine MRI alone, and SIJ MRI alone versus combined MRI, descriptively by the number/percentage of subjects according to the mean of four readers.


RESULTS
In cohorts A/B, 15.8%/24.2% of patients with nr-axSpA having a negative SIJ MRI were reclassified as being positive for SpA by global evaluation of combined scans. However, 26.8%/11.4% of non-specific back pain controls and 17.5% of healthy volunteers with a negative SIJ MRI were falsely reclassified as having SpA by combined MRI. Low confidence in a diagnosis of SpA by SIJ MRI increased to high confidence by combined MRI in 6.6%/7.3% of patients with nr-axSpA.


CONCLUSIONS
Combined spine and SIJ MRI added little incremental value compared with SIJ MRI alone for diagnosing patients with nr-axSpA and enhancing confidence in this diagnosis.
Department of Medicine, University of Alberta, Edmonton, Alberta, Canada Department of Rheumatology, Balgrist University Hospital, Zurich, Switzerland.
Ulrich
U
Weber
Department of Radiology, Balgrist University Hospital, Zurich, Switzerland.
Veronika
V
Zubler
Department of Rheumatology, PLA General Hospital, Beijing, China.
Zheng
Z
Zhao
Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada.
Robert G W
RG
Lambert
Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada.
Stanley M
SM
Chan
Copenhagen Center for Arthritis Research, Center for Rheumatology and Spinal Diseases, University of Copenhagen, Copenhagen, Denmark.
Susanne J
SJ
Pedersen
Copenhagen Center for Arthritis Research, Center for Rheumatology and Spinal Diseases, University of Copenhagen, Copenhagen, Denmark.
Mikkel
M
Østergaard
Rufibach rePROstat, Biostatistical Consulting and Training, Basel, Switzerland.
Kaspar
K
Rufibach
Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
Walter P
WP
Maksymowych
D000293:Adolescent; D000328:Adult; D001416:Back Pain / Q000209:etiology; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D013131:Spine / Q000000981:diagnostic imaging / Q000473:pathology*; D025241:Spondylarthritis / Q000150:complications / Q000175:diagnosis; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000175:diagnosis*; D055815:Young Adult
Ankylosing Spondylitis; Magnetic Resonance Imaging; Spondyloarthritis