• Manouk de Hooge, Rosaline van den Berg, Victoria Navarro-Compán, Monique Reijnierse, Floris van Gaalen, Karen Fagerli, Robert Landewé, Maikel van Oosterhout, Roberta Ramonda, Tom Huizinga, and Désirée van der Heijde.
• Rheumatology Department, Leiden University Medical Center, Leiden, The Netherlands.
• Ann. Rheum. Dis. 2016 Jul 1; 75 (7): 1308-14.

ObjectivesTo investigate the extent and performance of MRI lesions in the sacroiliac joint (MRI-SI) and spine (MRI-spine) in patients with suspected axial spondyloarthritis (axSpA).MethodsMRI-SI/spine of patients with chronic back pain (onset <45 years) in the SPondyloArthritis Caught Early (SPACE) cohort were scored by two well-trained readers for inflammation, fatty lesions, erosions, sclerosis/ankylosis and syndesmophytes. MRI performances were tested against the Assessment of Spondyloarthritis international Society (ASAS) axSpA criteria (positive: imaging-arm+ or clinical-arm+; negative: possible axSpA (few spondyloarthritis (SpA) features present) or no SpA). Arbitrary cut-off levels for MRI lesions were set to assure at least 95% specificity (tested in the no SpA group).ResultsIn total 126 patients were ASAS criteria positive (73 imaging-arm+ (22 by modified New York criteria (mNY)+; 51 by MRI+mNY-); 53 clinical-arm+) and 161 were ASAS criteria negative (89 possible axSpA and 72 no SpA). On MRI-SI (n=287), at least three fatty lesions (or at least three erosions) were seen in 45.5 (63.6)% of mNY+ patients, 15.7 (47.1)% of MRI+mNY- patients and 15.1 (13.2)% of clinical-arm+ patients versus 3.4 (6.7)% of possible axSpA patients and 2.8 (4.2)% of no SpA patients. A combined rule (at least five fatty lesions and/or erosions) performed equally well. Sclerosis and ankylosis were too rare to analyse. On MRI-spine (n=284), at least five inflammatory lesions (or at least five fatty lesions) were seen in 27.3 (18.2)% of mNY+ patients, 13.7 (21.6)% of MRI+mNY- patients and 3.8 (1.9)% of clinical-arm+ patients versus 4.5 (6.7)% of possible SpA patients and 2.9 (4.3)% of no SpA patients.ConclusionsThe presence of (1) at least five fatty lesions and/or erosions on MRI-SI, (2) at least five inflammatory lesions or (3) at least five fatty lesions on MRI-spine allows an acceptable discrimination of axSpA and no SpA, while assuring >95% specificity.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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