Lateral Flow Tests

Sea_Shell

GDB2222 said:

The thing is, though, that, most of the transmission is apparently by people who are asymptomatic. If we picked up just 76% of asymptomatic sufferers, and IF they self-isolated, we could reduce the R rate by roughly 76%. The cases of virus would then decrease exponentially very, very fast.

We could then either open up the economy more, or we could use the very low R to drive the infection rate to almost nothing and then reopen the economy. 

It would take around 4 weeks of everyone testing to drive the number of daily cases down from several thousand to just 2 or 3 individuals, and I think that even our test and trace people could handle that.  

There would be a lot of false positives, but these people should quickly get a PCR test, and they would only have to self-isolate for a day or two before any negative cases were told that.   

I didn't think that eradication was the government's plan.

I think we're going to have to live with a certain level of infection within society.

I'm not sure I want to live with the anxiety of what could almost become a "negative test before you can leave the house" situation.

Now that more and more are being vaccinated, we need to get on...live, make plans, do stuff.


However I can see the benefit of testing for specific circumstances, like before visiting someone in hospital, or if you feel you've been exposed.

JamoLew

Let’s just hope someone doesn’t do something silly like open the international borders too soon 🤦‍♂️

justworriedabit

What is the accuracy of these tests. Sure, a lot depends on if done properly but i read it wont give you a neegative if you have Covid but a 20% chance of saying you have covid when you don't.

Thanks for the link OP - Just ordered ours.

Thrugelmir

Sea_Shell said:

GDB2222 said:

The thing is, though, that, most of the transmission is apparently by people who are asymptomatic. If we picked up just 76% of asymptomatic sufferers, and IF they self-isolated, we could reduce the R rate by roughly 76%. The cases of virus would then decrease exponentially very, very fast.

We could then either open up the economy more, or we could use the very low R to drive the infection rate to almost nothing and then reopen the economy. 

It would take around 4 weeks of everyone testing to drive the number of daily cases down from several thousand to just 2 or 3 individuals, and I think that even our test and trace people could handle that.  

There would be a lot of false positives, but these people should quickly get a PCR test, and they would only have to self-isolate for a day or two before any negative cases were told that.   

Now that more and more are being vaccinated, we need to get on...live, make plans, do stuff.

Still a race to build immunity levels before the virus has a chance to mutate. Interesting that around 1:30 hospital admissions are for people who have received one jab. Suggests relaxation at a personal level is a little too quick. 

ladysummerisle

Just ordered some. I’m pregnant and my hospital insists on a test within 24 hours before allowing partners to attend scans. This is despite not testing the mothers! I’m hoping this will save arguments about whether he’s allowed in straight away or not..

Sea_Shell

Thrugelmir said:

Sea_Shell said:

GDB2222 said:

The thing is, though, that, most of the transmission is apparently by people who are asymptomatic. If we picked up just 76% of asymptomatic sufferers, and IF they self-isolated, we could reduce the R rate by roughly 76%. The cases of virus would then decrease exponentially very, very fast.

We could then either open up the economy more, or we could use the very low R to drive the infection rate to almost nothing and then reopen the economy. 

It would take around 4 weeks of everyone testing to drive the number of daily cases down from several thousand to just 2 or 3 individuals, and I think that even our test and trace people could handle that.  

There would be a lot of false positives, but these people should quickly get a PCR test, and they would only have to self-isolate for a day or two before any negative cases were told that.   

Now that more and more are being vaccinated, we need to get on...live, make plans, do stuff.

Still a race to build immunity levels before the virus has a chance to mutate. Interesting that around 1:30 hospital admissions are for people who have received one jab. Suggests relaxation at a personal level is a little too quick. 

But do we know if they got inflected within the immediate 3 week post vaccination period?

Batesy1976

Thrugelmir said:

Sea_Shell said:

GDB2222 said:

The thing is, though, that, most of the transmission is apparently by people who are asymptomatic. If we picked up just 76% of asymptomatic sufferers, and IF they self-isolated, we could reduce the R rate by roughly 76%. The cases of virus would then decrease exponentially very, very fast.

We could then either open up the economy more, or we could use the very low R to drive the infection rate to almost nothing and then reopen the economy. 

It would take around 4 weeks of everyone testing to drive the number of daily cases down from several thousand to just 2 or 3 individuals, and I think that even our test and trace people could handle that.  

There would be a lot of false positives, but these people should quickly get a PCR test, and they would only have to self-isolate for a day or two before any negative cases were told that.   

Now that more and more are being vaccinated, we need to get on...live, make plans, do stuff.

Still a race to build immunity levels before the virus has a chance to mutate. Interesting that around 1:30 hospital admissions are for people who have received one jab. Suggests relaxation at a personal level is a little too quick. 

So at current hospital admission rates, jsut short of 8 people a day?  Hardly a big problem.

Arthurian

silvercar said:

According to fullfact website:

99.68% of people who did not have the virus received a negative test result. In other words, very few people who do not have the virus which causes Covid-19 will be told wrongly that they do have it, after doing a lateral flow test.

However, the tests do return considerably more false negatives. Just 76.8% of people who did have the virus received a positive result (meaning the rest received false negatives). 

This percentage can vary though depending on how much virus is in the person’s system—the test detected over 95% of individuals with “high viral loads”.

It is a numbers game, so if you test 1 million people who don’t have covid, around 3,000 will wrongly have a positive result.

As we are in low covid times the current rate of infections is only 4 in a 1000. This means that if we tested 1 million people now around 4000 would have covid. But LFTs only pick up 76.8% of cases, so they would only pick up about 3,000.

So now we have 3,000 false positives and 3,000 correct positives. Hence people saying that half of all positive test results are wrong.

But in times when we have high covid rates, out of 1 million people you would get say 30,000 positives, so the ratio of correct positives to false ones is much higher.

So it seems we can trust the result we see on the lateral flow test if it says it's negative, but not so much if it says it's positive.  So couldn't we use them for travel abroad, then?  If it's a negative result, you're good to go.

Batesy1976

Arthurian said:

silvercar said:

According to fullfact website:

99.68% of people who did not have the virus received a negative test result. In other words, very few people who do not have the virus which causes Covid-19 will be told wrongly that they do have it, after doing a lateral flow test.

However, the tests do return considerably more false negatives. Just 76.8% of people who did have the virus received a positive result (meaning the rest received false negatives). 

This percentage can vary though depending on how much virus is in the person’s system—the test detected over 95% of individuals with “high viral loads”.

It is a numbers game, so if you test 1 million people who don’t have covid, around 3,000 will wrongly have a positive result.

As we are in low covid times the current rate of infections is only 4 in a 1000. This means that if we tested 1 million people now around 4000 would have covid. But LFTs only pick up 76.8% of cases, so they would only pick up about 3,000.

So now we have 3,000 false positives and 3,000 correct positives. Hence people saying that half of all positive test results are wrong.

But in times when we have high covid rates, out of 1 million people you would get say 30,000 positives, so the ratio of correct positives to false ones is much higher.

So it seems we can trust the result we see on the lateral flow test if it says it's negative, but not so much if it says it's positive.  So couldn't we use them for travel abroad, then?  If it's a negative result, you're good to go.

No, not at all.

The detection rate for people who are actually infected is really rather poor, as the post you quoted says.

silvercar

GDB2222 said:

The thing is, though, that, most of the transmission is apparently by people who are asymptomatic. If we picked up just 76% of asymptomatic sufferers, and IF they self-isolated, we could reduce the R rate by roughly 76%. The cases of virus would then decrease exponentially very, very fast.

We could then either open up the economy more, or we could use the very low R to drive the infection rate to almost nothing and then reopen the economy. 

It would take around 4 weeks of everyone testing to drive the number of daily cases down from several thousand to just 2 or 3 individuals, and I think that even our test and trace people could handle that.  

There would be a lot of false positives, but these people should quickly get a PCR test, and they would only have to self-isolate for a day or two before any negative cases were told that.   

The problem is the LFTs are more likely to pick up people with a high viral load, as those with symptoms have a higher viral load, I’m not sure that the tests pick up 76% of asymptotic sufferers.

there is also the problem that people make their own decision on whether to do the test. So those for whom life would be very difficult if they were positive and needed to isolate are less likely to test.