Promising new results for a blood test, “having a diagnosis as accessible as possible is crucial” – Libération

In a study published on July 28, Swedish researchers described a test that is 91% effective in detecting the disease, which could be used in specialized centers as well as in general practitioners. Jean-Charles Lambert, Inserm research director, comments on these results for “Libé”.

In France, 900,000 people suffer from Alzheimer’s disease; 225,000 are screened each year. And the figures will increase as the population ages. So research is getting active. On the one hand, the development of an effective treatment has been stalling for twenty years; on the other, that of diagnosis has made dazzling progress in recent years. It is in this context that the JAMAan international medical journal, published a study on July 28 that describes a blood test 91% effective to detect the disease.

With a simple blood test, this test measures the level of amyloid beta proteins and tau proteins – in the jargon, we speak of “biomarkers”. Their abnormal accumulation is associated with Alzheimer’s disease. Above all, the researchers’ goal was to limit its use: according to their results, the test could eventually be accessible in specialized centers as well as in general practitioners. For Jean-Charles Lambert, Inserm research director at the Pasteur Institute in Lille, this study shows once again that a “revolution is underway”. He comments for Liberation its main lessons.

How are the results described by this new study promising?

91% of correct diagnosis is huge. But this aspect was quite expected: this umpteenth result confirms the interest of the biomarker they use, a revolution underway for four years in the diagnosis of Alzheimer’s. They are an interesting aid to refine the diagnosis, particularly in the case of people who present objective cognitive and memory disorders. [c’est-à-dire évalués cliniquement par des tests neuropsychologiques, ndlr], but it cannot be said with certainty that it is dementia. If the test detects a high level of biomarkers, there is a high risk that these people will develop Alzheimer’s disease – although this is not systematic.

Does this mean that a simple blood test will soon allow us to know if we have Alzheimer’s?

Yes and no. This study will first have to be extended to other centres at the European level, to show that this tool works every time, regardless of where it is used. But since it was first presented three or four years ago, the development of this tool has been going very quickly: it is likely that it could be used in clinics within a few years, and a little later by treating physicians.

It also seems to me interesting to do such a blood test for forms of dementia already in place, or when patients are in the antechamber of the disease. On the other hand, we are not at the stage of doing this test ten years before the first symptoms to assess whether the person will develop it or not. I even find that there is an ambiguity in this study: the researchers suggest that this test could also be done on people with subjective cognitive disorders – they feel these disorders, but we do not find it in clinical tests. We can question the relevance of going that far.

Isn’t it crucial to detect the disease as early as possible?

Various studies show that the majority of people with these biomarkers will develop dementia, but this is not systematic. At this stage, I find this tool interesting as an aid to clinical diagnosis, combined with others. But it is also true that in the case of Alzheimer’s, the idea is to say that the earlier the treatment is taken, the more effective it will be… when we have an effective treatment. Today, immunotherapies, supposed to allow a slower progression of the disease, are very controversial: their effectiveness is limited and their side effects significant [raison pour laquelle l’Agence européenne du médicament vient de bloquer un nouveau traitement, ndlr].

So what is the use of these tests if there is no effective drug yet?

Making a diagnosis is never trivial, it is always useful. It opens up appropriate care, including financial, to support patients, as well as caregivers who are exhausted supporting their loved ones. In France, it is estimated that 40% of people with Alzheimer’s are not diagnosed; some arrive at the clinic in very advanced states of dementia. This is not acceptable. There are many factors, including societal ones – we still too often consider that it is “normal” for an elderly person to be unwell. We cannot replace families, who are often the first to detect the problem, but a blood test, which could be used by general practitioners, would make it possible to detect the disease earlier, or to recover undiagnosed patients.