Brain and spinal cord MRI and cerebrospinal fluid (CSF) examination obtained at CIS onset and a follow-up brain MRI acquired ≤15 months from CIS onset were assessed in 626 CIS patients from 9 European MS centres. The occurrence of a second clinical attack (clinically definite [CD] MS) was recorded. Performances of the 2017 and 2010 revised McDonald criteria for dissemination in space (DIS), time (DIT) and DIS+DIT, also including OCB assessment and median time to MS diagnosis for the different sets of criteria were evaluated.

At the last evaluation (median=61.9 months), 319 (51%) of 626 patients had CDMS. At 36 months, for DIS, the 2017 MRI criteria had higher sensitivity (0.84 vs 0.77), lower specificity (0.33 vs 0.40), and similar area under the curve values (AUC, 0.59). The 2017 DIS+DIT MRI criteria had higher sensitivity (0.68 vs 0.62), lower specificity (0.55 vs 0.62), and similar AUC values (0.62). CSF-specific OCB assessment increased the sensitivity (0.81), decreased specificity (0.40) and preserved AUC values of the 2017 criteria revision (0.60). Median time to MS diagnosis was earlier with the 2017 revision vs the 2010 or CDMS criteria, especially with OCB assessment (2017 revision+OCBs=3.6 months, 2017 revision without OCB=11.6 months, 2010 revision=13.9 months, CDMS=56.3 months).