A research team at LMU University Hospital is advancing the quest for more reliable and cost-effective diagnostic methods for Alzheimer’s disease. With the recent approval of Lecanemab by the European Medicines Agency (EMA) on November 14, 2024, the first drugs aimed at slowing the progression of Alzheimer’s are set to enter the German market. These therapies target amyloid plaques in the brain, raising the question of how to accurately diagnose their presence in patients with mild cognitive impairment or early-stage dementia—the primary candidates for such treatments.
The study, led by Professor Matthias Brendel, Acting Director of the Department of Nuclear Medicine, alongside Dr. Nicolai Franzmeier from the Institute for Stroke and Dementia Research and Professor Günther Höglinger, Director of the Neurological Clinic, has been published in the journal Alzheimer’s & Dementia: Diagnosis, Assessment, & Disease Monitoring. The findings may significantly influence patient management strategies.
Currently, two approved methods exist for detecting amyloid plaques in the brains of Alzheimer’s patients. The first method involves analyzing cerebrospinal fluid (CSF) through a spinal tap, an invasive procedure that carries some risks and is unsuitable for patients on blood thinners. Additionally, CSF analysis offers indirect and non-quantitative evidence of amyloid deposits.
The second method employs positron emission tomography (PET), a non-invasive imaging technique that provides direct, semi-quantitative evidence of amyloid presence in the brain. However, the cost of PET scans, ranging from €1,500 to €3,000, makes it inaccessible for many, as it is not currently covered by health insurance in Germany. Consequently, CSF analysis remains more common, despite the variations in availability and expertise across medical centers.
To assess the reliability of CSF tests compared to the gold standard of PET imaging, the LMU researchers analyzed data from over 400 patients suspected of having Alzheimer’s disease who underwent both tests between 2013 and 2024.
The study revealed that patients with CSF amyloid values above 7.1 typically had negative PET scans, indicating they did not have Alzheimer’s. Conversely, those with values below 5.5 predominantly showed abnormal PET results, suggesting a high likelihood of Alzheimer’s. Notably, a “gray area” existed for values between 5.5 and 7.1, affecting about 15 to 20 percent of patients. “Half of these study participants had abnormal amyloid results in their PET scans,” noted Professor Brendel, emphasizing that CSF alone is not sufficiently reliable in this range. The findings were corroborated by an independent cohort at the University of Vienna, reinforcing their validity.
As new amyloid-targeting drugs become available, the study’s insights could reshape diagnostic protocols. While amyloid PET should be prioritized where feasible, many patients in Germany currently have more accessible CSF analysis.
“From both medical and economic perspectives, it makes sense to start with CSF analysis unless there are specific medical reasons to opt for PET,” stated Professor Brendel. This approach could benefit approximately 70 to 80 percent of patients. Only those with ambiguous results in the 5.5 to 7.1 range would require additional PET scans. Brendel added, “If the costs of amyloid PET decrease in the future, it could become the preferred diagnostic method, helping to streamline the process and reduce unnecessary testing.”
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