Can someone more experienced with clinical work give their thoughts on the sensitivity and accuracy of this test? The group's paper reports:
sensitivity was 88.66% and specificity was 90.63%
My understanding is that this test will miss 12 in every 100 covid-19 infected individuals, and it will return a false positive for 10 in every 100 patients.
My intuition says this is more than acceptable for a rapid test. But I would love to see the opinion of someone with some clinical experience.
I don't think the quote you provided says anything about false positives; at least, I really hope it doesn't. A 10% false positive rate would be ridiculous. If 0.1% of the population has SARS-CoV-2, a test has a 10% false positive rate, and you get a positive result on that test, you only have about a 1% chance of actually being infected.
That's a little unintuitive, but here's how it breaks down, without taking into account false negatives:
* 10% of the population will receive a false positive
* 0.1% of the population will receive a true positive
Which category are you more likely to fall into--10% of the population or 0.1%? You're 100 times more likely to fall into the false positive category.
Nope, that is exactly what they are saying. It really is 10% false positive. They tested 128 negative blood samples and got a positive result for 12 of them. There is a frequency table at the end of their paper (0). So I guess you are right that if you sample a population of 1000 people (and only 1 actually sick) you would get 100 positive results, and 88% chance of detecting the one person who is actually sick.
Can't find the article now but there was two fast tests that got forbidden in Sweden yesterday because they miss a large percentage of the cases making it meaningless in best case or dangerous to others in worst case. You think you don't have corona so you go to work anyway even though you feel a bit sick.
A single false negative is worse than a single false positive, but false positives affect far more people with equivalent percentages. They’re both problematic, but in different ways.
Our medical infrastructure is already strained. If you tell 100x the number of actually infected people that they are infected, everything will grind time a halt.
It’s important to find a balance. A single false negative could be disastrous—but so could 1000 false positives. If the false negative and false positive rate are both 10%, and 0.1% of the population is infected, there will be 1000 false positives for every false negative. Both of those are going to cause huge (but very different) problems.
I only know the rate for the current German PCR Sequencer. They are at the industry standard of 3%, and require two tests per swab/person to get the higher accuracy required to avoid false negatives.
Remember, there’s probably a similarly high false negative rate. Also, take into account the number of people who won’t be going home, but will instead be flooding into ERs.
If you want to cause true mass hysteria and quickly overwhelm our already strained medical infrastructure, tell 10% of the population that that have SARS-CoV-2.
You need to stay home. There’s no way around it—certainly not for $20.
Comments
Can someone more experienced with clinical work give their thoughts on the sensitivity and accuracy of this test? The group's paper reports:
My understanding is that this test will miss 12 in every 100 covid-19 infected individuals, and it will return a false positive for 10 in every 100 patients.
My intuition says this is more than acceptable for a rapid test. But I would love to see the opinion of someone with some clinical experience.
I don't think the quote you provided says anything about false positives; at least, I really hope it doesn't. A 10% false positive rate would be ridiculous. If 0.1% of the population has SARS-CoV-2, a test has a 10% false positive rate, and you get a positive result on that test, you only have about a 1% chance of actually being infected.
That's a little unintuitive, but here's how it breaks down, without taking into account false negatives:
* 10% of the population will receive a false positive
* 0.1% of the population will receive a true positive
Which category are you more likely to fall into--10% of the population or 0.1%? You're 100 times more likely to fall into the false positive category.
Nope, that is exactly what they are saying. It really is 10% false positive. They tested 128 negative blood samples and got a positive result for 12 of them. There is a frequency table at the end of their paper (0). So I guess you are right that if you sample a population of 1000 people (and only 1 actually sick) you would get 100 positive results, and 88% chance of detecting the one person who is actually sick.
[0] https://rapidward.com/assets/downloads/Li_et_al-2020-Journal...
Can't find the article now but there was two fast tests that got forbidden in Sweden yesterday because they miss a large percentage of the cases making it meaningless in best case or dangerous to others in worst case. You think you don't have corona so you go to work anyway even though you feel a bit sick.
A false negative is worse than a false positive.
A single false negative is worse than a single false positive, but false positives affect far more people with equivalent percentages. They’re both problematic, but in different ways.
Our medical infrastructure is already strained. If you tell 100x the number of actually infected people that they are infected, everything will grind time a halt.
It’s important to find a balance. A single false negative could be disastrous—but so could 1000 false positives. If the false negative and false positive rate are both 10%, and 0.1% of the population is infected, there will be 1000 false positives for every false negative. Both of those are going to cause huge (but very different) problems.
I only know the rate for the current German PCR Sequencer. They are at the industry standard of 3%, and require two tests per swab/person to get the higher accuracy required to avoid false negatives.
Would a false positive bad in this situation if social distancing is required?
False negative would be more bad or am I missing something?
A 10% false positive rate for just about any test would render it mostly useless (see above).
The alternative of everyone staying at home has 100% false positive rate, so 10% is a huge improvement, not useless.
Remember, there’s probably a similarly high false negative rate. Also, take into account the number of people who won’t be going home, but will instead be flooding into ERs.
If you want to cause true mass hysteria and quickly overwhelm our already strained medical infrastructure, tell 10% of the population that that have SARS-CoV-2.
You need to stay home. There’s no way around it—certainly not for $20.