McDonald Diagnostic Criteria

About

The McDonald Diagnostic Criteria is a set of guidelines to help neurologists ensure they can provide an accurate diagnosis of multiple sclerosis. These diagnostic criteria have significantly shortened the time from first symptoms to confirmed diagnosis and earlier treatment initiation, improving long-term outcomes for people with MS.

These criteria were first developed in 2001 by an international panel of experts convened by the National MS Society and led by Dr. Ian McDonald. Since then, they have undergone several revisions to reflect advances in understanding multiple sclerosis. The most recent update—the fifth since their introduction—was completed in 2024 and published in The Lancet Neurology in September 2025.

2024 Revisions to the McDonald Criteria

The 2024 revisions reflect the work of the International Advisory Committee on Clinical Trials in MS (IACCTMS), comprised of 56 international experts from 16 countries across neurology, radiology, methodology, epidemiology, and patient advocacy. A formal consensus process was followed, requiring at least 80% agreement on proposed statements. Patient representatives also participated, ensuring the updated criteria reflect both scientific progress and lived experience.

The Lancet Neurology journal article: “Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria”

MS Research Spotlight on diagnosis of MS and the 2024 revisions of the McDonald Criteria

ECTRIMS Webinar on McDonald Criteria (published in May 2025)

ECTRIMS Press Release on the 2024 Revisions to McDonald Diagnostic Criteria for Multiple Sclerosis

National Multiple Sclerosis Society Press Release on Updates to McDonald Diagnostic Criteria for MS Published

The recommendations for updating the diagnostic criteria take into account new understanding of how MS appears and progresses in individuals. The recommendations demonstrate the shift towards considering the biologic basis of MS at diagnosis. The new criteria include tests that target what’s happening under the surface and the damage that is being caused by MS, in addition to the symptoms the person experiences.

To date, the recommendations include changes addressing where and how we look for evidence of MS, including new tests for diagnosis as well as specialised criteria for diagnosing children and people over 50.

These revisions aim to serve as “guidance for clinical practice worldwide,” said Dr. Tim Coetzee, Chief Executive at the National MS Society.

Prof. Jiwon Oh, Medical Director of the Barlo MS Program at St. Michael’s Hospital, University of Toronto, explains, “The key objective was to improve the sensitivity of the criteria, to make a correct MS diagnosis without delay, without compromising on specificity, to avoid misdiagnoses.”