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Sponsor: IRCCS San Raffaele

Conditions: Multiple Sclerosis

Countries: Austria, Czechia, Denmark, Germany, Italy, Netherlands, Norway, Spain

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system. Paramagnetic rim lesions (PRLs) are a subtype of chronic active MS lesions showing an iron-laden inflammatory rim on susceptibility-sensitive MRI. PRLs mark a more aggressive disease course and have recently been incorporated, together with the central vein sign, into the updated diagnostic criteria for MS. Before PRLs can be used reliably in multicenter clinical practice and trials, the way they are identified must be shown to be consistent across different centers, raters, and scanners. This is a retrospective, multicenter, observational validation study. Using previously acquired 3-Tesla brain MRI scans from MS patients across 15 MAGNIMS centers, expert raters count PRLs according to the NAIMS consensus definitions. The study measures how consistently PRLs are identified between centers, raters, and scanners (inter-rater, inter-center, and inter-scanner agreement), using statistical methods such as the intraclass correlation coefficient (ICC) and Bland-Altman analysis. Where systematic sources of disagreement are found, the PRL definitions are refined through a structured Delphi consensus process and re-tested on an independent set of scans. The goal is to standardize PRL identification and provide an evidence-based basis for consistent, reproducible PRL assessment to support future multicenter studies. No new patients are recruited and no new scans or biological samples are collected; only pre-existing, de-identified imaging and clinical data are used.