The new blood test for Alzheimer’s disease: developed in a study without patients

“Blood test is highly accurate at identifying Alzheimer’s before symptoms arise. When combined with age and genetic risk factor, test is 94% accurate.”

“Up to two decades before people develop the characteristic memory loss and confusion of Alzheimer’s disease, damaging clumps of protein start to build up in their brains. Now, a blood test to detect such early brain changes has moved one step closer to clinical use.”

It is these opening lines of the study’s press release that shaped the news. The Alzheimer’s Society reports that “Blood test is 94 per cent accurate at identifying early Alzheimer’s disease”; The Guardian that “Alzheimer’s blood test could predict onset up to 20 years in advance”; and also the doctors at WebMD highlight that “Blood test may spot signs of early Alzheimer’s.”

But no, the study didn’t test and track people for 20 years to see who ultimately developed Alzheimer’s disease. And the test wasn’t 94 per cent accurate in identifying early Alzheimer’s either. None of the participants in the study was diagnosed with Alzheimer’s disease. Their average score on the Mini Mental State Examination, a well-known test to measure cognitive impairment, was 29. As a reference: the test’s best possible score is 30, a score of 20 to 24 may indicate…