Forget the key again … Is that just “dodgy” or is there an Alzheimer’s disease? So far, this can only be clearly demonstrated using complex methods. However, according to a study, a simple blood test could soon clarify whether a patient has Alzheimer’s or whether the cognitive weaknesses are due to another cause. The rapid test could therefore give the all-clear or, if necessary, enable early treatment to slow progressive Alzheimer’s dementia.
We all forget something and it is also normal for mental performance to decrease with age. But millions of people are affected by cognitive decline that is far more dramatic. Alzheimer’s patients, for example, often forget their keys at first – however, in the advanced stage of the disease, they no longer understand their function. The causes of Alzheimer’s are still not fully understood. However, it is clear that two protein molecules play an important role: Amyloid beta and special tau proteins (pTau181) accumulate in the nerve cells and cause them to die. Alzheimer’s has not yet been curable. However, promising drugs are currently being developed that can delay the progression of the disease. Therefore, early treatment is important – but so far the diagnosis has been problematic.
Early diagnoses are problematic
Initially, Alzheimer’s symptoms are difficult to distinguish from other causes of poor mental performance. For example, frontotemporal dementia is often misdiagnosed as Alzheimer’s. Slight cognitive impairments can also have various other causes. To date, only complex diagnostic procedures can clarify whether Alzheimer’s actually exists: so-called positron emission tomography (PET) can detect the deposits in the brain and the detection of amyloid and tau proteins in the nerve water also enables a reliable diagnosis. But PET scans are expensive, only possible in specialized centers and the removal of nerve water is also complex and invasive. Practical and fast detection methods are therefore in demand.
In a previous study, a German research team was able to show that amyloid beta levels in the blood can provide clues to a person’s risk of developing Alzheimer’s. However, this method is not suitable as a diagnostic method for the onset of dementia, emphasize the researchers led by Adam Boxer from the University of California in San Francisco. Therefore, they have now explored whether an Alzheimer’s diagnosis based on the characteristic tau proteins (pTau181) in the blood is possible. These thread-like proteins are misfolded in Alzheimer’s patients and are therefore not broken down by the cells. As a result, they accumulate as much as the amyloid plaques.
Over 400 volunteers between the ages of 58 and 70 participated in the study. 56 of them had been diagnosed with Alzheimer’s by standard procedures, 47 had mild cognitive impairment, and 190 types had different types of frontotemporal dementia. The control group was made up of 69 healthy study participants. The content of pTau181 in the blood plasma was examined in all groups.
Promising results
As the researchers report, Alzheimer’s patients were clearly identified by the tau protein: the blood levels were more than twice as high as in all other groups. The pTau181 values were also in the normal range in patients with frontotemporal dementia. This finding is particularly important because the disease is often misdiagnosed as Alzheimer’s, the researchers emphasize. As they explain, the results now clearly show the potential of Alzheimer’s diagnosis via pTau181. The conclusion is that this procedure appears to be as reliable as the established detection via PET scans.
This is good news for the fight against Alzheimer’s disease: “This test could be used in medical practices in the future for people with memory problems to clarify whether someone should be referred to specialized centers,” says Boxer. “Being able to easily diagnose Alzheimer’s at an early stage can be particularly beneficial for patients with early cognitive impairment who have Alzheimer’s disease at an early stage of development. You could be more responsive to the new treatments that are being developed, ”says the scientist.
The drug aducanumab, for which approval has already been applied, is currently arousing particular hope. According to experts, it has the potential to effectively slow the progression of Alzheimer’s. Boxer and his colleagues now hope that their matching blood test for early Alzheimer’s diagnosis will be available in doctor’s offices in about five years.
Source: University of California – San Francisco, technical article: Nature Medicine, doi: 10.1038 / s41591-020-0762-2