Name: 敏感度較低的COVID測試的案例 (The Case for LESS Sensitive COVID Tests)
Uploaded: 2021-01-14T19:20:45.000Z
Duration: 6 min 41 s

It seems intuitive that a more sensitive COVID  test is better than a less sensitive one. And yet,  

似乎很直觀，靈敏度較高的COVID測試比靈敏度較低的好。然而：

程度副詞

you may also have seen news stories suggesting  that some COVID tests are too sensitive,  

您可能也看到過一些新聞報道，說一些COVID測試過於敏感。

情態助動詞 B1

or that cheaper, faster (and even less  sensitive?) tests might be better. But  

或者說，更便宜、更快（甚至更不敏感？）的測試可能更好。但是

why would they be better? And better for what? According to public health experts at Harvard  

為什麼他們會更好？好在哪裡呢？根據哈佛大學的公共衛生專家

and Brown University, in the fall of 2020 the  US needed to do 8x more testing to successfully  

和布朗大學，在2020年秋季，美國需要多做8倍的測試才能成功。

suppress COVID-19, India needed to do 4X more  testing, Brazil needed to do 66X more testing,  

抑制COVID-19，印度需要多做4倍的測試，巴西需要多做66倍的測試。

Bolivia needed to do 140X more testing, and  Mexico needed to do over 400X more testing.  

玻利維亞需要多做140倍的測試，墨西哥需要多做400多倍的測試。  

The idea behind saying “COVID tests are too  expensive and too sensitive” is that part  

說 "COVID測試太貴太敏感 "背後的想法是，部分

of what's kept countries from doing enough  testing is the kind of tests being used. 

使各國無法進行足夠測試的原因是所使用的測試種類。

The current gold-standard for COVID testing is a  nasal swab PCR [polymerase chain reaction] test.  

目前COVID檢測的金標準是鼻拭子PCR[聚合酶鏈反應]檢測。  

This test is highly sensitive, which means  it's able to detect the presence of the virus  

這種測試是高度敏感的，這意味著它能夠檢測到病毒的存在。

even at very low levels of viral load. That's  great for a doctor who wants to know whether  

即使是在非常低的病毒載量水準。這對醫生來說是很好的，他們想知道是否

their patient was infected with COVID-19. But if  you're screening an entire community for COVID  

他們的病人感染了COVID -19。但如果你要對整個社區進行COVID的篩查的話

outbreaks, then PCR tests have a few downsides. First, PCR tests are expensive. To avoid breaking  

爆發，那麼PCR檢測有幾個缺點。首先，PCR檢測價格昂貴。為了避免打破

the bank, many places are focusing on testing only  people who already have COVID symptoms or who were  

銀行，很多地方只注重檢測已經有COVID症狀的人，或者是被

recently exposed to someone with COVID. Using  only expensive tests means that we don't test  

最近接觸到COVID的人。只使用昂貴的測試意味著我們不測試。

(and therefore, don't catch!) most people who  are contagious without showing symptoms – and  

(是以，不會傳染!)大多數人在沒有表現出症狀的情況下就會被傳染--而且。

we know that a significant proportion of COVID  transmission comes from these asymptomatic people. 

我們知道，COVID的傳播很大一部分來自於這些無症狀的人。

Second, PCR tests take time: usually a couple of  days for results to come back from the lab. Here's  

其次，PCR檢測需要時間：通常需要幾天的時間才能從實驗室得到結果。下面是

what the typical viral load in an infected person  looks like over time – they're most infectious  

感染者的典型病毒載量隨著時間的推移是什麼樣的--他們的傳染性最強。

around the peak and their infectiousness declines  afterwards. So if test results take a few days to  

高峰期前後，之後其傳染性就會下降。所以，如果檢測結果需要幾天時間才能

come back, chances are you miss this peak – which  means missing the window of time during which the  

回來，你有可能會錯過這個高峰--這意味著錯過了時間窗口，在這段時間裡，你會發現，你會發現，你會發現，你會發現，你會發現，你會發現，你會發現。

person is most likely to infect other people. Essentially, although PCR is very sensitive,  

的人最有可能感染其他人。基本上，雖然PCR非常敏感。

it's also expensive and slow, so while it's great  for diagnosis, it may not be the best test for  

它也是昂貴的和緩慢的，所以雖然它是偉大的診斷，它可能不是最好的測試為

screening a community. And the cheaper, faster  testing alternatives are – no surprise – not as  

篩選一個社區。而更便宜、更快速的測試替代品--不足為奇--並不是那麼好用。

sensitive as PCR. BUT - and this is a subtle point  and maybe wouldn't matter if PCR were cheap and  

敏感的PCR。但是--這是個微妙的問題，如果PCR很便宜，也許就無所謂了。

fast, BUT when it comes to screening a community,  PCR's high sensitivity could itself be a downside.

快，BUT在篩查一個社區時，PCR的高靈敏度本身就可能是一個缺點。

PCR tests can detect very low viral loads, which  is great if you happen to test somebody very  

PCR檢測可以檢測出非常低的病毒載量，這是很好的，如果你碰巧測試某人非常。

early on in an infection, or very late and you  want to confirm whether they were infected. But  

在感染的早期，或很晚，你想確認他們是否被感染。但是

this sensitivity also means that a person can  test positive for the infection when they're  

這種敏感性也意味著一個人可以測試陽性的感染時，他們的。

basically no longer infectious – and in fact, PCR  is so sensitive that it can detect viral fragments  

基本上已經不具備傳染性--事實上，PCR的敏感度非常高，可以檢測到病毒的片段

and give a positive result even when there are  no viable viruses left. So it's likely that by  

並給出一個陽性結果，即使是沒有活病毒了。所以很可能通過

using PCR tests we're quarantining & contact  tracing some people when we don't need to. 

利用PCR測試，我們在不需要的時候對一些人進行隔離和接觸追蹤。

It's not that the PCR test is a bad test, in fact  it's a great test for what it's designed to do,  

並不是說PCR測試不好，事實上，它是一個很好的測試，它的目的是什麼。

which is to accurately and reliably detect even  very low viral loads. It's just that it's more  

也就是準確可靠地檢測出即使是很低的病毒含量。只是，它更

expensive, slower, and perhaps even more sensitive  than would be ideal for screening a community. 

昂貴、緩慢，甚至可能比篩查一個社區的理想狀態更加敏感。

A less sensitive test could catch just  as many highly infectious people as PCR,  

敏感度較低的檢測方法，可以像PCR一樣抓到很多高傳染性的人。

but it would miss people who are post-infectious,  which you could argue is a good thing for  

但會錯過那些感染後的人，你可以說這是一件好事，對於

screening purposes since those people  are no longer a significant threat. The  

由於這些人不再是重大威脅，所以要進行甄別。該

downside is that you'd also miss people who are  pre-infectious, which is undoubtedly a bad thing. 

缺點是，你還會錯過那些前期傳染的人，這無疑是一件壞事。

But the math works out that if you have a test  that's just a little bit less sensitive than PCR,  

但算下來，如果你有一個測試，只是比PCR的靈敏度低一點。

but you use it a lot more frequently,  you're actually more likely to detect an  

但你用得多了，你實際上更有可能發現一個

infection compared to infrequent PCR testing.  So can you identify more infections overall. 

與不頻繁的PCR檢測相比，感染。  所以，你能不能從整體上識別出更多的感染。

All of this suggests that if you're trying  to screen a community for COVID outbreaks,  

所有這些都表明，如果你想篩選一個社區的COVID爆發。

you can get more testing bang for your  buck with rapid testing than PCR testing;  

與PCR檢測相比，你可以通過快速檢測獲得更多的檢測效果。

that is, you can identify more infectious  people more quickly for less money.  

就是說，你可以用較少的錢更快地識別出更多的傳染病人。  

As long as the rapid tests are only slightly  less sensitive than PCR tests but a lot cheaper. 

只要快速檢測的靈敏度只比PCR檢測略低，但價格便宜很多。

Rapid testing is not a replacement  for PCR testing in a clinical setting,  

在臨床上，快速檢測不能代替PCR檢測。

nor is it a replacement for masks,  physical distancing, handwashing,  

也不能代替口罩、物理距離、洗手。

and so on. And if PCR testing cost 1/10th  of what it does and took 1/10th the time,  

等等。而如果PCR檢測的成本是它的1/10，花費的時間是1/10。

we probably wouldn't be having this discussion.  But if we're going to test widely and frequently  

我們可能就不會有這樣的討論了。  但是，如果我們要廣泛和頻繁地測試

enough to suppress COVID (and we really  should), then we can get more for our money  

足以壓制COVID（我們真的應該），那麼我們就可以得到更多的錢。

with tests that are cheaper, faster, and - perhaps  counter-intuitively - a little bit less sensitive. 

的測試，這些測試更便宜、更快速，而且--也許與直覺相反--靈敏度更低一些。

Ok, so that's the argument for rapid  testing, and here are the caveats. 

好了，這就是快速測試的論點，下面是注意事項。

No medical tests are perfect, and a negative test  result isn't a foolproof guarantee of not being  

沒有任何一項體檢是完美的，陰性的檢查結果也不能保證不被

infected. Because rapid tests are less sensitive  than PCR tests, this makes it more likely that  

感染。由於快速檢測的靈敏度低於PCR檢測，這使得更有可能的是

infected people will slip through the cracks  of a test. So as long as COVID is a problem,  

感染者會從測試的縫隙中溜走。所以只要COVID是個問題。

it's important to still take precautions  like wearing a mask and social distancing  

重要的是，還是要採取預防措施，比如戴上口罩，與社會保持距離。

even if you test negative. And for  people who were likely exposed to COVID,  

即使你的測試是陰性的。而對於那些很可能接觸到COVID的人來說。

health authorities recommend that they quarantine  for 14 days regardless of a negative test result,  

衛生部門建議，無論檢測結果是否為陰性，都要隔離14天。

and that their negative rapid test  results are verified by a PCR test. 

並通過PCR檢測驗證其陰性快速檢測結果。

When a rapid test is just a little less  sensitive than PCR, then the downsides of  

當快速檢測的敏感度僅比PCR低一點時，那就會出現弊端。

missing some infected people can be balanced out  by the benefits of more widespread and frequent  

錯過了一些感染者，可以通過更廣泛和更頻繁的好處來彌補。

testing. But this only works up to a point. If  the sensitivity of the rapid test is too low,  

測試。但這隻能起到一定的作用。如果快速檢測的靈敏度太低。

the cost of missing many infections will  outweigh the benefits of widespread testing. 

遺漏許多感染的成本將超過廣泛檢測的好處。

The graph we showed for viral load was based  on measurements of patients' viral loads,  

我們展示的病毒載量圖是基於對患者病毒載量的測量。

and while all else being equal, a higher viral  load tends to mean you're more infectious,  

而在其他條件相同的情況下，病毒含量越高，往往意味著你的傳染性越強。

there are a lot of other things that  can affect how infectious you are 

有很多其他的事情，可以影響你的感染力

We didn't really mention what happens when you  aren't infected but the test gives a positive  

我們並沒有真正提到當你沒有被感染時會發生什麼，但測試給出了一個陽性的

result anyway – this isn't likely on any given  test, BUT if you're testing a huge number of  

結果--這在任何給定的測試中都是不可能的，但是如果你在測試大量的

people frequently, then just by statistics alone  you can end up with a large number of false  

的人，那麼僅憑統計就可以最終獲得大量的虛假的

positive results. The rate of false positives  is comparable between PCR tests and rapid tests,  

陽性結果。PCR檢測和快速檢測的假陽性率相當。

but matters more with cheap rapid tests  since the whole idea is to do way more tests. 

但對於廉價的快速測試來說，問題更多，因為整個想法是做更多的測試。

Finally, vaccines. So won't all of this  be irrelevant once vaccines come out?  

最後是疫苗。那麼疫苗一出來，這些是不是就都不重要了呢？  

Well, vaccines will certainly help, but  unfortunately, testing will probably still  

好吧，疫苗肯定會有幫助，但不幸的是，測試可能還是會。

play a major role in suppressing COVID.  It's really a topic for another video.

在壓制COVID方面發揮了重要作用。  這真的是另一個視頻的話題。

A very big thankyou to Brilliant  for sponsoring this episode of  

非常感謝Brilliant對本期節目的贊助。

MinutePhysics - with MinutePhysics, I try  to bring you deeper level explanations,  

MinutePhysics--通過MinutePhysics，我試圖為你帶來更深層次的解釋。

while Brilliant engages you to solve  fascinating, challenging problems yourself,  

而Brilliant則讓你自己去解決迷人的、具有挑戰性的問題。

guiding you to a deeper level understanding  of science and mathematics. Like their course  

引導你對科學和數學有更深層次的理解。像他們的課程

on knowledge and uncertainty - what's the most  efficient way to zero in on the true criminal  

關於知識和不確定性 -- -- 什麼是最有效的方法來鎖定真正的罪犯？

from a lineup of suspects? Or, how worried  should you be if you know a medical test is 90%  

從一眾嫌疑人中脫穎而出？或者說，如果你知道體檢的結果有90%是假的，你該有多擔心？

sensitive and you get a positive result? To improve your knowledge and reduce your  

敏感，你就會得到一個積極的結果？為了提高自己的知識水準，減少自己?

uncertainty, go to brilliant.org/MinutePhysics/  and sign up for free. The first 200 people will  

不確定性，請到 brilliant.org/MinutePhysics/ 並免費註冊。前200人將

get 20% off the annual Premium subscription,  with full access to all of Brilliant's courses,  

獲得20%的年度高級訂閱優惠，並可享受所有Brilliant的課程。

puzzles, & daily challenges. Again,  thanks to Brilliant for their support.

謎題，和每日挑戰。再次感謝Brilliant的支持。

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敏感度較低的COVID測試的案例 (The Case for LESS Sensitive COVID Tests)

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