MRVAS-introducing a standardized magnetic resonance scoring system for assessing the extent of inflammatory burden in giant cell arteritis

Our aim was to introduce a standardized system for assessing the extent of GCA on MRI, i.e. the Magnetic Resonance Vasculitis Activity Score (MRVAS). To obtain a comprehensive view, we used an extensive MRI protocol including cranial vessels and the aorta with its branches. To test reliability, MRI was assessed by four readers with different levels of experience. A total of 80 patients with suspected GCA underwent MRI of the cranial arteries and the aorta and its branches (20 vessel segments). Every vessel was rated dichotomous [inflamed (coded as 1) or not (coded as 0)], providing a summed score of 0-20. Blinded readers [two experienced radiologists (ExR) and two inexperienced radiologists (InR)] applied the MRVAS on an individual vessel and an overall level (defined as the highest score of any of the individual vessel scores). To determine interrater agreement, Cohen's κ was calculated for pairwise comparison of each reader for individual vessel segments. Intraclass correlation coefficients (ICCs) were used for the MRVAS. Concordance rates were excellent for both subcohorts on an individual vessel-based (GCA: ICC 0.95; non-GCA: ICC 0.96) and overall MRVAS level (GCA: ICC 0.96; non-GCA: ICC 1.0). Interrater agreement yielded significant concordance (P