The Alzheimer’s breakthrough that isn't

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A new blood test for Alzheimer's disease is 87% accurate. That's a big story, right? Not so fast, according to the British NHS Choices site, which complained that none of the news coverage "reported the positive predictive value of the test. This reduces the impressive sounding 87% accurate figure to around the 50% level … giving the test the same predictive value as a coin toss." More from Gary Schwitzer, John Gever.