A Nature Communications study mapped how tau species evolve in both plasma and cerebrospinal fluid (CSF) during Alzheimer’s disease progression, providing new “trajectories” for biomarkers rather than isolated snapshots. Researchers led by Collij, Salvadó, Horie and colleagues tracked MTBR-tau243 and multiple tau species, linking their temporal patterns across blood and CSF compartments. The work strengthens the case for using blood-based tau assays to mirror disease biology traditionally observed in CSF, while highlighting that the kinetics of different tau species can diverge across matrices.