The McDonald criteria allow an accurate diagnosis of multiple sclerosis. In everyday clinical practice, however, they are often used incorrectly – with considerable risks for patients.
Multiple sclerosis is the most common neuro-immunological disease in Germany and other western countries. Since it affects young people particularly often, it causes enormous health and economic costs. Fortunately, effective therapies are available that can prevent an increase in disease-related disability in many cases. Enormous sums of money are spent on the development of better and better medicines and so the therapeutic arsenal grows year by year.
A prerequisite for good therapy is an accurate diagnosis. The McDonald criteria are used to diagnose multiple sclerosis. These criteria were first presented in 2001 and are updated every few years to reflect the latest findings. The criteria were last revised in 2017. The criteria are based on the knowledge that MS is a disease that progresses in phases (i.e. events that are separated in time) and affects different regions of the central nervous system. One speaks of a temporal and spatial dissemination. In order to be able to diagnose MS, these two aspects must be met. They must be demonstrated by clinical, imaging, or other diagnostic findings. In addition, symptoms typical of MS must still exist and differential diagnoses must be ruled out. Only then can the diagnosis of MS be made.
Errors in the application of the McDonald criteria can lead to two situations – both of which are associated with significant risks for the patients concerned. On the one hand, the diagnosis of multiple sclerosis cannot be made or can only be made with a delay, although MS is actually present. Drug therapy does not take place in this case or is delayed. It is known, however, that the course of the disease can best be positively influenced in an early phase of the disease with immunomodulatory therapy. Depriving a patient of effective drug therapy can lead to increased physical disability and suffering that could have been prevented.
On the other hand, if the McDonald criteria are not applied with care, the diagnosis of MS can be made even though another disease or perhaps only non-specific symptoms or imaging changes are actually present. In this case, the patient may be given highly active immunomodulatory and usually also immunosuppressive therapy. And even if the drugs are effective in MS, like all drugs, they sometimes have significant side effects. In addition, it is known that some MS medications can even have a negative effect on the course of similar diseases. This is the case with NMOSD (Neuromyelitis Optica Spectrum Disorder), where beta interferon therapy can result in increased disease activity.
In order to avoid the serious mistakes mentioned above as far as possible, there are the McDonald criteria, which are always adapted to the latest state of research. If they are used correctly, an accurate diagnosis is possible. But this is exactly where the problem lies. Various studies show that the criteria are sometimes incorrectly applied by neurological specialists, including MS specialists, due to gaps in knowledge or misunderstandings. A group of researchers led by Andrew Solomon from the University of Vermont, USA, tested different groups of neurologists using the diagnostic criteria. This revealed considerable difficulties.
In a first Studythe 2020 im Multiple Sclerosis Journal published, comparing the performance of neurology residents and MS specialists. Not surprisingly, the MS specialists were more confident in applying the diagnostic criteria than the residents, but many errors were made in both groups. One aspect that was very often ignored (by 50% of residents and at least 16% of MS specialists) is the requirement for the application of the McDonald criteria that symptoms typical of an MS relapse must exist. In the case of non-specific symptoms, the criteria should not be applied, otherwise false-positive results will occur. This was obviously not known to many study participants. Another aspect that caused problems was the exact knowledge of the locations typically affected in the MRI. While the theoretical knowledge was available (most participants could identify the four typical locations of MS lesions juxtacortical, periventricular, infratentoriell and spinal name), there was a problem with the practical implementation. Only 39% of residents and 52% of MS specialists were able to correctly identify juxtacortical MRI lesions in sample images. Many participants also failed to correctly identify the other typical localizations.
In a second Study The same research group, which was published in the same journal in 2022, finally examined specific doctors who stated that they frequently diagnosed MS in their clinical practice. This study is therefore probably even more relevant for the quality of MS diagnosis in everyday clinical practice. And in this group, too, the same knowledge gaps or misunderstandings often led to errors. In a case study, 43% did not recognize that the symptoms described were not typical relapse symptoms and that the McDonald criteria should therefore not be used. And on the practical questions about the location of lesions depicted in MRI images, only 5% of the participants did well.
Whether similar problems exist in Germany has not yet been proven by studies. However, one can assume that neurologists in this country have at least some similar misunderstandings. This underlines the importance of improving teaching in medical studies, in specialist training and in further professional training. Because even if the diagnosis of multiple sclerosis is carried out carefully and accurately in the majority of cases, there is always room for improvement. And that can be used.
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