The evolution of disease criteria in multiple sclerosis: underlying motives and broader implications

Disease criteria for multiple sclerosis (MS) have changed significantly over the past three decades. The development of biomarkers, particularly MRI, has played an essential role in this process. These changes can lead to several broader implications, which are not always intended or recognized. However, they can have a major impact on patients, healthcare and society. We investigated the changing disease criteria, explored the underlying motives and discuss their implications.

We identified all publications on MS diagnostic criteria between 1983 and 2024. Through conventional content analysis, we systematically examined the aims of each revision and identified the underlying problems and factors motivating these aims. Furthermore, we assessed the changes made to the content in each revision.

Since the transition from the Poser research criteria to the McDonald clinical criteria in 2001, there has been a significant change in the aims of the criteria, which has continued in subsequent McDonald revisions. Two explicit new aims were to integrate MRI into the diagnostic scheme and to reach an earlier diagnosis of MS whenever possible. Furthermore, the emphasis moved towards criteria that are easy to apply in everyday clinical practice, rather than being exclusively for research purposes. This shift is at least partially connected to the emergence of disease-modifying treatments, which have introduced new diagnostic and monitoring needs. Additionally, advancements in MRI research have contributed to this process. As a result, MRI has become central to the diagnostic criteria over the years, while clinical symptoms now play a much smaller role.

The shift in the criteria has several broader implications. It has a major impact on how MS is conceptualized as a disease and has expanded the disease spectrum to include new terms such as radiologically isolated syndrome (RIS). It also influences our understanding of the natural course of the disease and calls for a careful balance between early diagnosis and misdiagnosis. Awareness of the process of changes and their broader consequences can help balance the benefits and potential negative effects and helps critically frame the decisions of the 2024 revisions.