Giant Cell Arteritis: Diagnostic Accuracy of MR Imaging of Superficial Cranial Arteries in Initial Diagnosis-Results from a Multicenter Trial

Purpose: To assess the diagnostic accuracy of contrast material-enhanced magnetic resonance (MR) imaging of superficial cranial arteries in the initial diagnosis of giant cell arteritis (GCA). Materials and Methods: Following institutional review board approval and informed consent, 185 patients suspected of having GCA were included in a prospective three-university medical center trial. GCA was diagnosed or excluded clinically in all patients (reference standard [final clinical diagnosis]). In 53.0% of patients (98 of 185), temporal artery biopsy (TAB) was performed (diagnostic standard [TAB]). Two observers independently evaluated contrast-enhanced T1-weighted MR images of superficial cranial arteries by using a four-point scale. Diagnostic accuracy, involvement pattern, and systemic corticosteroid (sCS) therapy effects were assessed in comparison with the reference standard (total study cohort) and separately in comparison with the diagnostic standard TAB (TAB subcohort). Statistical analysis included diagnostic accuracy parameters, interobserver agreement, and receiver operating characteristic analysis. Results: Sensitivity of MR imaging was 78.4% and specificity was 90.4% for the total study cohort, and sensitivity was 88.7% and specificity was 75.0% for the TAB subcohort (first observer). Diagnostic accuracy was comparable for both observers, with good interobserver agreement (TAB subcohort, kappa = 0.718; total study cohort, kappa = 0.676). MR imaging scores were significantly higher in patients with GCA-positive results than in patients with GCA-negative results (TAB subcohort and total study cohort, P < .001). Diagnostic accuracy of MR imaging was high in patients without and with sCS therapy for 5 days or fewer (area under the curve, >= 0.9) and was decreased in patients receiving sCS therapy for 6-14 days. In 56.5% of patients with TAB-positive results (35 of 62), MR imaging displayed symmetrical and simultaneous inflammation of arterial segments. Conclusion: MR imaging of superficial cranial arteries is accurate in the initial diagnosis of GCA. Sensitivity probably decreases after more than 5 days of sCS therapy; thus, imaging should not be delayed. (C) RSNA, 2014