Applying the new McDonald criteria increases the rate of MS diagnosis

The 2024  revision of the McDonald criteria for diagnosing multiple sclerosis (MS) enables earlier and more frequent diagnosis compared with the 2017 criteria. A retrospective observational study demonstrated that the revised criteria allow the diagnosis of 43% more patients with MS at baseline.

Study presenter Dr Luca Bollo (Vall Hebron University Hospital, Spain) outlined the key changes in the 2024 McDonald criteria [1]. The optic nerve can now serve as a fifth anatomical location within the CNS. The central vein sign, paramagnetic rim lesions, and kappa-free light chain concentrations in cerebrospinal fluid (CSF) can serve as supportive markers, thereby increasing diagnostic specificity. In some instances, radiologically isolated syndrome or neurological symptoms that do not constitute an apparent attack or progression of disability can fulfil the criteria for MS.

Dr Bollo and colleagues conducted a comparison study to evaluate the impact of the 2017 versus 2024 McDonald criteria in 326 patients with suspected MS and to assess the effect on time to diagnosis [2]. Inclusion criteria required incidental MRI findings, an attack with symptoms and signs characteristic of MS, or objective progression from the onset of symptoms.

The mean age was 39.0 years, and 67.3% were female. The median observation period was 2.6 years. Of the 326 participants, 164 (50%) met the 2017 McDonald criteria, and 234 (72%) met the 2024 McDonald criteria. Stratified by inclusion criteria, the rates were as follows:

• Among the 237 subjects (73%) with a clinical attack, 141 (59%) met the McDonald 2017 criteria, and 176 (74%) met the 2024 criteria.
• Among the 40 subjects (12%) with objective progression, 23 (57%) met the McDonald 2017 criteria, and 33 (83%) met the 2024 criteria.
• Among the 49 subjects (15%) with incidental MRI findings, 0 met the McDonald 2017 criteria, and 25 (51%) met the 2024 criteria.

Overall, the 2024 criteria diagnosed more patients than the 2017 criteria, both at baseline (71% vs 47%; P<0.001) and at follow-up (83% vs 60%; P<0.001). In total, the 2024 revisions to the McDonald criteria allowed for a 43% increase in the proportion of patients diagnosed with MS, resulting in an earlier diagnosis compared with the 2017 criteria (HR 1.43; 95% CI 1.17–1.74; P<0.001).

1. Montalban X, et al. Lancet Neurol. 2025;24(10):850-865.
2. Bollo L. Impact of the 2024 McDonald criteria revisions on multiple sclerosis diagnosis: a comparison with the 2017 criteria. O001, ECTRIMS 2025 Congress, 24-26 September 2025, Barcelona, Spain.

Medical writing support was provided by Michiel Tent.

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Posted on 26 September 2025