Lateral Flow Tests

silvercar

onthebench said:

GDB2222 said:

Initially, people were worried that the swabbing would be painful, but it really isn’t. Ticklish, yes, but not painful. 

I have done a couple of tests, and I found it difficult to self administer the swabs. It helps to use a mirror. Or get someone else to do it for you.

I hate the throat swabs. In fact just thinking about it is triggering my gag reflex now. I’ve found the only way I can do it is as quickly as possible, which then tends to make it a bit painful as I end up stabbing my tonsils. 

Then do both nostrils and not your throat. I’ve been doing this for weeks, nostrils only, and haven’t had a void result yet.

GDB2222

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.

I don't think Silvercar would agree with your interpretation. 

If the test says you are positive, there is a 99.9% chance that you are. There's also around a 24% chance that it will miss your infection. That's why you may not be allowed to use it for travel.

For travel, the destination country wants a test with a very high chance of picking up any infection. They don't care (much) if you are well, but the test says you are ill and can't travel.

silvercar

justworriedabit said:

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.

Other way round. The chances of it giving you a positive if you don’t have covid is about 1 in 200. The chances of it picking up that you do have covid is around 3 in 4.

squirrelchops2

We have been given the LFD tests to do twice weekly via our work. Initially they said just to do nasal swab but after a few weeks amended their advice to do both throat and nasal like would be done if you had the PCR test.
We have to record on a form for work that initially was just shared in house so to speak, however this has also altered to have a disclaimer saying that the outcomes are now shared with track and trace!

bluenose1

There is no evidence that mass testing asymptomatic population is of any benefit, in fact with false positives/ negatives it could increase potential spread. There was a research paper cited in Nature that suggests transmission from asymptomatic people is highly unlikely anyway. However we continue to throw money at unproven testing.

The only time I would get tested, is if I had symptoms and it would be a PCR test. 
I dread to think what all  this unnecessary testing is costing the country financially for no gain.

Tokmon

silvercar said:

onthebench said:

GDB2222 said:

Initially, people were worried that the swabbing would be painful, but it really isn’t. Ticklish, yes, but not painful. 

I have done a couple of tests, and I found it difficult to self administer the swabs. It helps to use a mirror. Or get someone else to do it for you.

I hate the throat swabs. In fact just thinking about it is triggering my gag reflex now. I’ve found the only way I can do it is as quickly as possible, which then tends to make it a bit painful as I end up stabbing my tonsils. 

Then do both nostrils and not your throat. I’ve been doing this for weeks, nostrils only, and haven’t had a void result yet.

A test is only void if there isn't enough test medium to get to the control line so whether or not is void has nothing to do with where you collect the sample from with the swab or if you have done the sample collection properly. 

silvercar

bluenose1 said:

There is no evidence that mass testing asymptomatic population is of any benefit, in fact with false positives/ negatives it could increase potential spread. There was a research paper cited in Nature that suggests transmission from asymptomatic people is highly unlikely anyway. However we continue to throw money at unproven testing.

The only time I would get tested, is if I had symptoms and it would be a PCR test. 
I dread to think what all  this unnecessary testing is costing the country financially for no gain.

The point is to pick up positives before people show symptoms as well as the asymptotic. 

There is the risk that false negatives give people a (false) sense of security and could engage in ‘reckless’ behaviour. 

Thrugelmir

Batesy1976 said:

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.

The continuing transmission of Covid is. Long Covid could become an issue for a far greater number of people. 

wannabe_a_saver

Thrugelmir said:

Batesy1976 said:

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.

The continuing transmission of Covid is. Long Covid could become an issue for a far greater number of people. 

Continuing restrictions cause harm too. 

What is really needed now is for the government to start funding the NHS to deal with the fact that Covid as an endemic virus.  More staff, more beds, research into how to best treat long covid. 

Batesy1976

Thrugelmir said:

Batesy1976 said:

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.

The continuing transmission of Covid is. Long Covid could become an issue for a far greater number of people. 

It's not going away. People need to accept that. Long COVID, deaths, etc are just something people are going to have to accept.