MAPT and Alzheimer disease: CSF biomarkers are increasingly used in many memory clinics because of the high diagnostic accuracy and relatively low costs, and several CSF AD biomarker assays have recently been approved for clinical use by the US Food and Drug Administration.20,21 Still, lumbar puncture is invasive, but some novel blood-based biomarkers are reaching diagnostic accuracies that are similar to those of CSF AD biomarkers,6,22 which is why such blood markers will likely precede a decision to perform tau PET imaging in most memory clinics in the coming years.