The McDonald Diagnostic Criteria is a set of guidelines to help neurologists ensure they can provide an accurate diagnosis of multiple sclerosis. The criteria were first developed in 2001 by an international panel of experts convened by the National MS Society (USA) and led by Dr. Ian McDonald, a New Zealander. 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, published in The Lancet Neurology in September 2025 and announced in Barcelona at European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS).
How are the diagnostic criteria agreed?
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.
What’s new in 2024?
The 2024 updates include changes to where and how we look for evidence of MS, expanding the ways MS can be diagnosed and including new tests in the diagnosis process. These additions have been made whilst maintaining the core criteria from the previous versions.
- Faster diagnosis: in some situations the requirement for ‘dissemination over time’ (meaning there is evidence of a relapse or specific symptoms occurring at more than one time point) has been removed, enabling some people to receive an MS diagnosis without waiting months or years for a second relapse or attack of symptoms.
- Expanded diagnostic evidence: Previously, there had to be evidence of nerve damage in two out of four areas of the brain and spinal cord to demonstrate ‘dissemination over time’. Now, it’s possible to include damage to a fifth area, the optic nerve, as well. This opens opportunities for collaboration with ophthalmologists and the use of optical coherence tomography (OCT) or visual evoked potential tests, if available.
- Radiologically Isolated Syndrome (RIS): People with evidence on an MRI scan of nerve damage in the central nervous system (CNS) – even without the usual clinical symptoms of MS – may now meet the criteria for MS if other factors are met. Previously, these individuals would have had to wait until symptoms of MS developed to be diagnosed; the new criteria provide the opportunity for earlier diagnosis, treatment and monitoring.
- Specialised guidance: The criteria contain new considerations for diagnosing children and people over 50, recognising that MS can be harder to distinguish from other conditions in these age groups.
What does this mean for New Zealanders
Multiple Sclerosis NZ is seeking expert clinical advice on the revised McDonald Criteria and how this might impact diagnosis in Aotearoa. We will be reviewing how we might need to advocate, communicate and support the implementation of the revised criteria, improving accuracy and speeding up diagnosis and improving patient outcomes.
For most people with a diagnosis of MS the revised criteria will have no effect on you. For some with a questionable diagnosis, undergoing or yet to be diagnosed, this could speed up the process and in the long-term improve health outcomes.
Read more:
- MS International Federation: Understanding the updated McDonald criteria for diagnosing MS – MS International Federation
- ECTRIMS: McDonald Diagnostic Criteria | ECTRIMS
This information has been prepared thanks to the MS International Federation and ECTRIMS.