Date: Monday, November 9, 2015
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: Diffusion weighted imaging (DWI) is an MRI protocol which assesses the random Brownian motion of water molecules in the tissue imaged; this motion is restricted in inflamed tissue. Previous studies have suggested that this approach may have diagnostic potential in AS. We sought to test the diagnostic capacity of DWI, and to assess its potential an objective measure of treatment response to TNF-inhibition, in AS.
Methods: Three cohorts were studied: 1. 18 AS patients with BASDAI>4 and ESR>25 and/or CRP>10 meeting the modified New York Criteria for AS; 2. 20 cases with non-radiographic axial SpA as defined by the ASAS criteria, and 3. 20 non-AS patients with chronic low back pain >3 months duration aged >18 years but <45 years. Group 1 patients were studied immediately prior to and following 14 weeks of treatment with adalimumab 40mg s/c fortnightly. All Group 2 patients met the imaging arm of the ASAS criteria and 13 also met the clinical criteria. Ten Group 3 patients met the ASAS clinical criteria, but none met the imaging criteria, and all were assessed as having non-inflammatory back disease clinically. Patients were assessed by DWI (right and left iliac ADC measures corrected for sacral background measure), BASDAI, BASFI, BASMI, ASDAS-CRP, CRP and ESR. Patients on corticosteroids were excluded, and NSAID and analgesic medications were kept stable during the follow-up study of Group 1 patients.
Results: At baseline BASDAI, BASFI, BASMI, ASDAS-CRP, CRP and ESR levels were increased in Group 1 patients, but similar between Group 2 and 3 patients (CRP levels were increased in Group 2 vs 3 patients). Post treatment Group 1 patients had lower BASDAI, BASFI, ASDAS-CRP, and similar BASMI, CRP and ESR levels, compared with either Group 2 or 3 patients. ROC curve analysis showed that none of these measures individually discriminated between Group 1 and 2 patients vs non-inflammatory controls (AUC values 51-74%). In contrast DWI ADC values showed good discriminatory performance (AUC 86%, P<10-5, sensitivity 88%, specificity 81%). The AUC for G2 vs G3 was similarly high (90%, P<10-5, sensitivity 90%, specificity 85%). DWI ADC scores correlated poorly with other disease activity measures (correlation coefficients -0.27 to +0.36, overall dataset). Comparing patients pre and post adalimumab treatment, BASDAI, BASFI, ASDAS-CRP, ASDAS-ESR, CRP and ESR had high discriminatory performance (AUC 99%, 81%, 99%, 97%, 95% and 88% respectively). DWI ADC values were significantly lower post adalimumab treatment (0.45±0.433 pre, 0.154±0.23 post, P=0.022), but had only modest discriminating capacity (AUC 64%).
Conclusion: DWI imaging is informative for diagnosis of AS and non-radiographic axial spondyloarthritis, but has only moderate utility in assessment of disease activity or treatment response.
To cite this abstract in AMA style:Bradbury LA, Hollis KA, Gautier B, Shankaranarayana S, Robinson P, Saad N, Lê Cao KA, Brown MA. Diffusion Weighted Imaging Is a Sensitive and Specific MRI Protocol for the Diagnosis and Assessment of Disease Severity in Ankylosing Spondylitis [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/diffusion-weighted-imaging-is-a-sensitive-and-specific-mri-protocol-for-the-diagnosis-and-assessment-of-disease-severity-in-ankylosing-spondylitis/. Accessed June 7, 2020.
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