Reply With QuoteYes, very aware and being applying that process for some time within the team I manage.
If anyone would be so kind. I am looking to see if people are generally aware that...
If you have symptoms that could be covid a lateral flow test is not useful and doesn't mean you do not have covid if it is negative.
If you have symptoms you should self-isolate and get a PCR test.
The lateral flow test is very poor at picking up cases and therefore not useful if you're base likelihood is increased by the presence of symptoms. They are only useful as a regular screen if you do not have symptoms.
There is no judgement involved here I am just wondering if people are a)aware of that b)not aware c)aware but choose not to act on it.
Last edited by watchstudent; 7th July 2021 at 13:38.
Yes, very aware and being applying that process for some time within the team I manage.
I'm so glad we've got a thread to discuss things like this on after all this time!
I disagree with some of your vaguely worded criticisms of Antigen/LatFlow tests but you'd have to be more specific about things like "very poor at picking up cases" and "marginally useful as a regular screen".
If you're simply asking if people understand that, if symptomatic, they should self-isolate and arrange for a PCR test rather than LatFlow, I'd like to think so but I suspect many don't. A bigger and more important question is what are the reasons for symptomatic people not self-isolating at all or taking any form of test.
Sure.Originally Posted by MakeColdplayHistory
The lateral flow test has a very poor sensitivity, it’s hard to study but available evidence points to the sensitivity being between 76.8 and 57.5%. That means that if you have COVID then there is possibly an over 40% chance a lat flow will be negative. It has a very high “false negative” rate. Kind the opposite of what is needed. It is a “rule in, not a rule out” test. If the test is positive, it’s very likely you have it, if you have a negative test, there is still a good chance you have it. So if your odds of having it are already increased due to symptoms a negative test is just not helpful.
It’s ok as a screen for asymptomatic people. Because if you have 10 COVID cases with no symptoms and no one does a test then all those cases will go around spreading it. If they all take a test then maybe between 5 and 7 of them will get a positive result and hopefully isolate. An ok result, not great.
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Last edited by watchstudent; 7th July 2021 at 12:57.
Unfortunately this sort of post is akin to the majority of the mainstream media coverage of lateral flow testing (not helped by some manufacturer claims, especially in the earlier months of covid).
LFAs play an important role in the overall diagnostic toolkit. They are excellent tools for screening, and should be used as such to support wider diagnostic testing efforts. If a LFA comes back positive then it is almost certain you are currently infected because they are highly specific.
However as the OP says they are not as sensitive as molecular tests, so a negative result does not definitively mean you are not infected with covid, and you should continue to presume you are potentially positive with all the preventative measures that go along with that.
Use them for what they’re designed for and they are highly valuable diagnostic tools. LFAs are sold in their hundreds of millions and are a major part of the fight against malaria. Let’s not diminish their value.
I always thought this too, and just did the LFT at times for the sake of it.
However, recently (in the last two weeks) have spoken to two people who developed symptoms, so went home and did the LFT. Both showed positive. They then went to get a PCR to confirm - both positive.
It has certainly increased my belief around the usefulness of LFT. Granted, a sample of two means nothing, but clearly they can work well.
Agreed. A useful quick screening test.
Basically I wasn’t actually trying to get into the pros and cons, just if people were aware or not about the way they are supposed to be used.
Anecdotally, I am seeing 90% of people with symptoms claiming they don’t have COVID due to a negative lat flow. Just wanted to spread the net a little wider to see what the consensus was on a very demographically skewed forum like this!
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That use case is totally fine and what you would expect. If someone has positive test they are nearly 100% likely to have covid. The issue comes with when the test is negative and people assume that means they don’t have Covid despite symptoms.
So basically, if those two people had negative tests, they still should have gotten a PCR.
LFT rules Covid in, it doesn’t rule it out.
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Last edited by watchstudent; 7th July 2021 at 13:21.
The difficulty here is that most people on this forum are not medically qualified, or have the appropriate scientific training to be able to understand the difference between sensitivity/specificity and false +ve/-ve results. That's understandable, but the conflicting assertions from people who lack the appropriate background to comment with authority that this post will inevitably generate are most likely going to add to the confusion. I might add that the threads that pop up about PSA testing on here just go to prove this.
I am medically qualified and I agree with watchstudent's second post here. It describes the issue with these tests. Some of the blind faith that has been placed in them by the government has astonished me. The worst example was in schools, where a positive lateral flow test could not be overriden by a subsequent negative PCR.
I do think most folks ‘get’ the general idea now. It just hasn’t been helped by the many ill-informed articles that have appeared in the press (both overly pro and con) on the subject.
Discussing it openly is definitely a good thing though!
Yes, I was mainly hoping to gauge what the issue is - awareness/understanding vs unwillingness to comply.
Quite useful to get thoughts of people outside of my medically qualified bubble. Although I think most people should be able to understand it without a medical qualification! It’s more statistics anyway. Just needs to be explained clearly. Which I may or may not have done…
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Last edited by watchstudent; 7th July 2021 at 13:35.
What are the symptoms?
Yes, fully aware of the benefits and limitations of both. I've used the evidence from research reports on efficacy of testing to inform suitable control measures for numerous COVID-19 Risk Assessments.
Don't just do something, sit there. - TNH
Working in the NHS, we have to test daily. A colleague of mine, having had both jabs tested negative in both lateral flow and PCR.
Someone in his 'bubble' got COVID, so he had to isolate too. It later transpired that he was the one that passed it on to her.
Obviously this was most probably just a freak coincidence, but it goes to show that not everything can be relied upon 100%.
I work in an industry where I have to have a works PCR before being allowed to mobilise. I caught Covid at the end of June, did my isolation then on the 18th July I reported to work to do a PCR test, all lateral flows had been negative, my PCR came back as detected so I had to go back home and isolate again for another ten days even though lateral tests at home and a further PCR test showed negative.
Total PITA and it’s cost me money, tried to explain that I shouldn’t be doing PCR tests in a 90 day period after having covid as they can still pick up traces, even my company admits the was the case but they have to follow the guidelines…
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proof of covid recovery (letter from a doctor ) should be used instead of another PCR test in those circumstances within a 90day period
I was convinced I had the 'rona - lateral flow showed negative then two days later a pcr also showed negative. by then I had been more than 10 days off sick at home anwyay so maybe it just cleared up enough for the PCR test who knows.
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