The flaw in that Alzheimer's story

<a href='http://www.shutterstock.com/pic.mhtml?id=115815166'>Image via Shutterstock</a>

John Gever looks at the statistics in the Alzheimer's blood-test study that made the news last week, and what he finds suggests that many reporters missed a crucial detail — the test's low "positive predictive value" for cognitive impairment. Giving the test to 1,000 patients, Gever writes, "produces a total of 140 positive results, 45 of which are correct and 95 false." Because there's no followup test to weed out the false positives, the test may have little value.

March 18, 2014

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