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Simple blood tests sound pretty good. So how accurate are they?
简单的血液测试听起来相当不错。那么它们的准确度如何呢？
Turns out they’re good, at least at connecting what’s in your blood to what’s in your brain.
事实证明它们很好，至少将血液中的物质与大脑中的物质相联系。
Amyloid starts in your brain, and some drifts down your spine in your cerebrospinal fluid. From there a little tiny bit leaks out into your blood.
淀粉样蛋白始于大脑，一些淀粉样蛋白沿着脊髓向下流，进入脑脊液中，流经此处，少量淀粉样蛋白会渗漏到血液中。
One test, called Precivity AD, can detect the proteins with 93 percent accuracy, according to one study.
一项研究表明，一种名为Precivity AD的测试可以检测出淀粉样蛋白，准确率达到93%。
Another test, AD Detect, just launched by the big national diagnostic lab Quest, does it at close to the same rate.
另一项刚刚由大型国家诊断实验室Quest推出的AD Detect测试，准确率也几近相同。
That’s compared to the gold standards in Alzheimer’s diagnostic tests.
这样的准确率可以与阿尔茨海默病诊断测试的黄金标准相比。
And those gold standard tests are a lot more complicated to do.
而黄金标准测试做起来要复杂得多。
One is a lumbar puncture of the spine, using a needle to draw out spinal fluid.
一种是腰椎穿刺，用针抽出脊髓液。
The other is a brain scan called PET that uses a special dye to highlight clumps of amyloid in your brain.
另一种是名为PET的脑部扫描，用一种特殊染液突出脑内的淀粉样蛋白团块。
Those are the two best at finding amyloid.
这两种测试是发现淀粉样蛋白的最佳方法。
Though doctors will more often start a diagnosis by giving people sophisticated memory tests.
尽管医生通常会通过对患者进行复杂的记忆测试来开始诊断。
Obtaining a thorough medical history, performing a physical neurologic exam, getting labs, neuroimaging, typically that is how we had diagnosed Alzheimer's disease.
获得全面的病史，进行物理神经检查，做实验室检查，做神经影像，通常这就是我们诊断阿尔茨海默病的方法。
That is Alzheimer’s expert Zaldy Tan.
以上是阿尔茨海默病专家扎尔迪·谭的发言。
I'm a memory disorder specialist as well as medical director of the Yona Goldbridge Center for Alzheimer's disease at Cedars Sinai Medical Center in Los Angeles, California.
我是一名主治记忆障碍的专家，也是加州洛杉矶西达赛奈医疗中心(Cedars Sinai Medical Center)约纳·金桥阿尔茨海默病中心的医学主任。
Did Tan mention why doctors want blood tests if they already have these lumbar punctures that work well?
谭有没有提到，如果医生已经有了效果很好的腰椎穿刺，为什么还要验血?
As a matter of fact, he did.
事实上，医生确实可以做。
First of all, patients don't like it very much when you do that.
不过，首先，患者并不喜欢做腰椎穿刺。
It involves, you know, a pretty long needle that.. you have to stick in someone's back and get a sample.
这包括，医生必须用一根长针从患者背后刺入，取出样本。
Ouch! That sounds painful.
哎哟! 听起来就很痛苦。
No kidding. And as for the PET scans, there are not a lot of places around the country that do them, so there’s a long wait.
没有开玩笑。至于PET扫描，全国做PET扫描的地方并不多，所以要等很长时间。
Plus they’re expensive and insurance may not cover them.
此外，PET扫描价格昂贵，医保也不可以覆盖。
I can see why a blood test would be more convenient.
我明白为什么验血会更方便。
So the idea is that if tests show you have brain amyloid, you could take drugs that help, right?
这个想法是，如果测试显示大脑中有淀粉样蛋白，那么你便可以服用有用的药物，对吗?
Right.
没错。
I sense there’s a “but” coming...
我感觉有个“但是”要来了……
Yep. And here it is.
是的。以下就是。
We don't routinely look for amyloid in the workup for someone with memory issues because there's a subset of individuals who will get amyloid positivity without having disease.
我们通常不会通过做全身检查寻找淀粉样蛋白来诊断某人患有记忆问题，因为一小部分人不患有这种病也会出现淀粉样蛋白阳性的现象。
So what he’s saying is, tests for amyloid can be positive, but people can still be fine mentally?
他的意思是，淀粉样蛋白的检测结果可能呈阳性，但人们的精神状况仍然可以正常吗?
Exactly. He went into more detail.
没错。他谈到了更多细节。
There is a study that’s almost 10 years old now, where they followed close to 3,000 individuals.
有一项研究已经进行了近10年，他们跟踪调查了近3000人。
And what they found was that people who are age 50, who don’t have memory issues, even in formal testing, 10 percent of them will be amyloid positive.
他们发现，即使在正式测试中，50岁的无记忆问题的实验者中也有10%的人淀粉样蛋白呈阳性。
And if you look at people who are 90 years old, about 45–50 percent of them will be amyloid positive.
如果你看看90岁的实验者中，约45% - 50%的人淀粉样蛋白呈阳性。
Again, these are people who do not have memory issues and therefore do not have dementia.
同样，这些人没有记忆问题，因此也没有痴呆症(阿尔茨海默病)。
