5 Key Takeaways

• 1

  Direct serum testing found elevated brain-derived tau and p-tau217 in patients with Alzheimer’s disease and amyotrophic lateral sclerosis compared with disease controls.

• 2

  Researchers used antibody-coated magnetic beads to enrich brain-derived tau before measuring tau and p-tau217 in a subgroup of the multicenter cohort.

• 3

  After enrichment, brain-derived tau and brain-derived p-tau217 were elevated in Alzheimer’s disease but not in amyotrophic lateral sclerosis.

• 4

  For distinguishing Alzheimer’s disease from amyotrophic lateral sclerosis, p-tau217’s area under the curve rose from 0.729 with direct testing to 0.900 after enrichment.

• 5

  Mass spectrometry found brain-derived tau predominated in frontal cortex and big tau in skeletal muscle, supporting muscle-derived tau as a potential source of blood-test confounding.