Does the Addition of DWI to Fluid-Sensitive Conventional MRI of the Sacroiliac Joints Improve the Diagnosis of Sacroiliitis?

ABSTRACT

OBJECTIVE: The purpose of this study was to determine whether adding DWI to conventional MRI of the sacroiliac joints improves the diagnostic performance of MRI readers in the detection of sacroiliitis. MATERIALS AND METHODS: MR images of the sacroiliac joints of 63 patients with lower back pain obtained between January 2016 and December 2016 were analyzed retrospectively. Three readers reviewed the MRI studies for bone marrow edema lesions around the sacroiliac joints as a marker of active sacroiliitis and gave a diagnostic confidence score of 0-4 using MRI without DWI and MRI with DWI in separate sessions. The normalized apparent diffusion coefficient mean (nADCmean) was measured. Clinical and radiologic data using the Assessment of Spondyloarthritis International Society criteria were the reference for the diagnosis of sacroiliitis. Diagnostic performance, confidence scores, and interreader agreement for the MRI methods were compared. The nADCmean values of patients with and those without sacroiliitis were compared. RESULTS: The accuracy, sensitivity, and specificity of MRI without DWI were 68.3%, 69.0%, and 67.6% and for MRI with DWI were 74.6%, 69.0%, and 79.4% (accuracy and sensitivity, p > 0.100; specificity, p = 0.039). The mean confidence score for MRI without DWI was 3.60 and for MRI with DWI was 3.67 (p = 0.270). The kappa coefficient for MRI without DWI was 0.28 and for MRI with DWI was 0.46 (p = 0.041). The nADCmean in patients with sacroiliitis was 3.86 and in patients without sacroiliitis was 1.6 (p ≤ 0.001). The nADCmean AUC was 0.758 (95% CI, 0.67-0.83). CONCLUSION: The addition of DWI to conventional MRI does not significantly improve overall diagnostic performance in terms of accuracy, sensitivity, or confidence in the detection of inflammatory sacroiliitis, but it does have increased specificity and interobserver agreement. ADC threshold values can be used as predictors of sacroiliitis but give no added advantage over MRI with DWI.