A peer-reviewed comparison found that tau signals in blood can reflect tissues beyond the brain. Selecting brain-derived tau before measurement improved separation between Alzheimer’s disease and ALS in a smaller sample. The extra step did not significantly improve every diagnostic comparison, and its complexity limits immediate use as a routine screening procedure.
A single peer-reviewed study found that selecting brain-derived tau before a blood measurement improved separation of Alzheimer’s disease from amyotrophic lateral sclerosis, or ALS, a disease affecting motor neurons. Direct serum assays showed elevated tau signals in both diagnostic groups. After isolation, only the Alzheimer’s samples retained elevated values. ALS cases and disease controls no longer differed significantly.[1]
The main clinical comparison included a disease-control group of 75 people alongside 101 Alzheimer’s cases and an ALS group numbering 139. For the two-step test, the team analysed 39 disease-control samples, together with samples from 50 ALS patients and 60 people with Alzheimer’s. An antibody-based step selected brain-derived tau before measurement. Discrimination between Alzheimer’s and disease controls, already strong, did not improve significantly. The observational comparison tested no treatment, and the additional procedure remains complex and limited in availability.[1]
Mass spectrometry of brain, spinal cord and muscle samples showed different mixtures of tau forms. Brain-derived tau predominated in brain tissue; a larger form had its greatest relative contribution in muscle. In muscle, big tau carried phosphorylation at the protein’s 217 position. These tissue findings support peripheral contributions to blood signals, without providing a direct inventory of every tau form circulating in blood. Absolute concentrations also differed between processing methods.[1]
