Multiple sclerosis diagnostic criteria: three years later.

New diagnostic criteria for multiple sclerosis (MS) were developed by an International Panel in 2001 and have had wide distribution and discussion since publication. These provided the first formal incorporation of magnetic resonance imaging (MRI) in a diagnosis work-up for patients suspected of having MS. The so-called McDonald criteria have been studied in retrospective and prospective analyses for sensitivity, specificity and utility, and have been proven to compare favourably or to be an improvement upon prior MS diagnostic criteria. The purpose of the current review is to present and evaluate the key studies that have been performed using the McDonald criteria since 2001 and to set the stage for an upcoming re-evaluation of the new criteria based on data-driven information gathered since their development.