Recent studies suggest blood levels of phosphorylated tau (p-tau) isoforms can detect both the tau and amyloid pathologies that define Alzheimer disease (AD).1 More research is needed to replicate these results in large, diverse cohorts and quantify a p-tau blood test’s ability to prognosticate the onset of dementia. Nevertheless, we anticipate that the ability to receive diagnostic and prognostic information with the ease of a blood test will revolutionize AD research and care. We also anticipate that it will be the basis of a profitable direct-to-consumer (DTC) test, one that highlights considerable ethical and social challenges of DTC testing and AD.