Now we know there is a link between our gut and Alzheimer’s disease, as we saw in yesterday’s post.
One of the problems with researching the disease is properly identifying patients with Alzheimer’s. Right now, we need to do PET (positron emission tomography) scans or spinal taps to analyze the cerebrospinal fluid- both of these are expensive and extensive testing. The goal of those tests is to discern the parameters of Aβ-PET, tau-PET, CSF Aβ42:Aβ40 ratio, and the presence of CSF Tau phophorylated at threonine 181 (P-tau181).
The plasma levels of P-tau181 for those with Alzheimer’s (average of 8.4 pg/mL) are 3.5X those not suffering from Alzheimer’s (2.4 pg/mL)- so it renders differentiation between Alzheimer’s, frontotemporal lobar degeneration, and other neurodegenerative conditions possible. But, very recently, it was determined that P-tau217 yields even more distinctive results than P-tau181.
Actually, the concentration correlates well with what is called the tangle density score. We know that tau protein accumulates after Aβ deposits are found; it is tau that is correlated as the primary driver of cognitive decline. But atrophy is not directly related to tau deposits of normal cortical thickness; it’s when the protein tangles develop that atrophy begins. The presence of tangles is associated with the regions where the brain is likely to shrink as Alzheimer’s develops.
Dr. Oskar Hansson (Lund University and Skane Hospital, Norway), along with Drs. S. Palmqvist, S. Janelidze, E. Stomrud, A. Leuzy, N. Mattsson-Carlgren, O. Strandberg, and R. Smith from Lund; Drs. Y.T. Quiroz, F. Lopera, A. Villegas, and D. Sepulveda-Falla of Universidad de Antioquia, Medellin, Colombia; Drs. Y. Su and E.M. Reiman plus Mr. Y Chen of Banner Alzheimer’s Institute of Arizona; Dr. G. Serrano and T. Beach of Banner Sun Health Research Institute (Arizona); Drs. H. Zetterberg and K. Blennow of Gotteburg University (Sweden); and Eli Lilly’s Mr. N.K. Proctor and Dr. J. Dage, tested 1402 subjects for the levels of P-tau181 in plasma. They reported their results, Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs Other Neurodegenerative Disorders, in JAMA.
Given that a blood test is much simpler and cheaper than requiring a spinal tap or a PET scan, these results are very encouraging. The results demonstrated that plasma p-tau217 effectively separated out those with Alzheimer’s from those with other neurodegenerative diseases- much better than MRI (magnetic resonance imaging) biomarkers and with results equivalent to the CSF and PET tests.
Moreover, this test was able to help clinicians discern whether the patient has dementia or is suffering from Alzheimer’s. Actually, it helps determine if folks with cognitive issues are actually manifesting early onset Alzheimer’s. Which means we can better design treatments for the condition, since we can actually declare who has Alzheimer’s and who doesn’t. So, the drugs can be tested ONLY for those with Alzheimer’s, not those who may have the disease.
The question is whether the test will let physicians determine if subjects with NO symptoms may actually be on track to develop Alzheimer’s.
