ECTRIMS 2025: Updated McDonald criteria enable more MS diagnoses
2024 revisions increase proportion of people who can be diagnosed
The new revisions to the McDonald criteria for multiple sclerosis (MS) — a set of guidelines long used to diagnose the neurodegenerative condition — have increased the proportion of people who can be diagnosed with MS and also allow for earlier diagnoses.
That’s according to a new analysis by scientists at the Multiple Sclerosis Centre of Catalonia in Spain. The findings were presented by Luca Bollo, a neurologist specialist at the center, at the 41st Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS), held Sept. 24-26 in Barcelona, Spain, and online.
Bollo’s talk was titled “Impact of the 2024 McDonald criteria revisions on multiple sclerosis diagnosis: a comparison with the 2017 criteria.”
MS is a disorder marked by inflammation that damages healthy cells in the central nervous system (CNS), which comprises the brain and spinal cord. The McDonald criteria are guidelines used to diagnose MS based on clinical findings, imaging tests, and laboratory analyses. First published in 2001, the guidelines have been updated several times as scientific understanding of MS has evolved.
The most recent update is the 2024 version, which was just published last week. The 2024 revisions build upon those in a prior update, published in 2017. The aim is making the diagnosis of MS faster and more accurate.
The 2024 updates include several notable changes, such as providing new guidance on interpreting certain imaging findings and biomarker data. A particularly important change, as noted by researchers, is that, in prior versions of the criteria, patients could only be diagnosed if they showed dissemination in time — meaning neurological damage occurring at multiple points in time.
With the new revisions, the McDonald criteria no longer require dissemination in time to diagnose MS if enough other signs of the disease are present. This means that patients may not have to wait several months or even years for new disease activity to occur to receive an MS diagnosis.
2024 revisions to McDonald criteria widen scope
The previous version of the criteria also assessed neurological damage in just four key regions — three brain areas and the spinal cord. The 2024 update incorporates a fifth region: the optic nerves, which connect the eyes to the brain.
Under the 2024 revisions, MS can now be diagnosed without further testing if at least four of these five regions show disease-typical damage and the patient is experiencing MS-like symptoms.
Also, under the earlier McDonald criteria, MS could not be diagnosed if only one region showed damage. These newest revisions allow the diagnosis of MS in some situations when only one region is affected.
To show how these changes may impact MS diagnoses moving forward, Bollo and colleagues looked at clinical data from 326 people who were evaluated for suspected MS at their center between January 2022 and March 2025. Among the patients, about two-thirds were female and the average age was 29.
“Our objective [was] to compare the impact of the 2017 and 2024 McDonald criteria in a cohort of patients [with] suspected MS, and to evaluate their effect on time to diagnosis,” Bollo said.
Most of these patients (73%) were being evaluated for MS because they had experienced an attack of symptoms that clinicians suspected might be an initial MS flare. Of these patients, 74% met the 2024 criteria for a diagnosis of MS. Using the 2017 criteria, 59% of these individuals would have been diagnosed with MS, Bollo noted.
Another 12% of the patients were being evaluated for MS because they’d been experiencing slowly worsening symptoms indicative of progressive MS. With the 2024 criteria, 83% of these patients were diagnosed with MS. According to Bollo, 57% would have been diagnosed with the 2017 criteria.
The remaining 15% of patients were being evaluated because MRI scans had revealed signs of MS-like damage — even though these individuals had no obvious symptoms.
The 2024 update notably includes several changes aimed at making it easier to diagnose MS in such situations. Slightly more than half of these patients were diagnosed with MS according to the latest criteria. Importantly, the analysis found that none of them could have been diagnosed according to the 2017 criteria.
Significantly more patients can now get a definitive MS diagnosis
The researchers noted that every patient who met the 2024 criteria for MS could also be diagnosed according to the earlier 2017 criteria, but the reverse wasn’t true. Overall, significantly more patients could be definitively diagnosed according to the 2024 criteria (72% vs. 50%), the data showed.
Statistical analyses revealed that patients evaluated according to the 2024 criteria were 42.7% more likely to be diagnosed with MS, and that the time to diagnosis was significantly faster, by about six months under the 2024 revisions as compared with the earlier 2017 criteria.
Bollo concluded that “the 2024 revisions to the McDonald criteria increase the proportion of patients diagnosed with MS by 43%” compared with the prior updates. The scientist also noted that, with these updates, the McDonald criteria “allowed for an earlier diagnosis.”
Note: The Multiple Sclerosis News Today team is providing live coverage of the 41st Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Sept. 24-26. Go here to see the latest stories from the conference.
About the Author
