A review challenged the scientific validity of the FDA-cleared Lumipulse G p-tau217/Aβ1–42 plasma ratio, arguing the Alzheimer’s diagnosis performance has flaws. Authors from the University of Barcelona reviewed evidence around the biomarker approach and raised concerns that the ratio may not behave consistently as an effective discriminator across clinical contexts. The critique matters for biotech diagnostics because blood-based Alzheimer’s tests are increasingly being used for earlier detection and patient stratification. Any evidence that undermines the ratio’s interpretability can accelerate follow-on validation efforts or prompt revisions in diagnostic guidance. For the industry, the publication signals that even established, cleared assays remain subject to ongoing scrutiny as independent groups test performance assumptions in real-world datasets.