The biology of coronavirus COVID-19 - including research and treatments

Leila said:
Is LFT a rapid test?
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Yea LFT is the abbreviation for lateral flow test and it misses positive infections (compared to a PCR - the gold standard test but still not 100%). Interesting that there seems to be a lag between being symptomatic and a positive LFT --- presumably PCR would be +ve in this lag period.

Wonder if the LFT tests are not as good in detecting this variant?
 
Jonathan Edwards said:
Yes, our daughter was doing daily LFTs and got badly ill with what was almost certainly omicron and only came positive on LFT around the fifth day. It looks as if LFT is a waste of time as an indicator of preclinical infection. My wife was negative too, when ill having caught it off our daughter.
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I'm hearing more and more stories of people catching Omicron from people with negative LTF. I hope you, your wife and your daughter are OK.
 
Snow Leopard said:
No, it means LFTs have poor sensitivity.

In my state you can't even buy LFTs for that reason...
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Interesting. Here they are used widely and given out freely. Folk often use them before going out, and a PCR is only offered if you have symptoms.

Perhaps for Delta (and earlier variants) it was mostly useful, but as I understand things Omicron replicates much much faster, so maybe an LFT some hours before an event is already out of date?

Agree though the LFTs seem fairly hopeless for Omicron.
 
Snow Leopard said:
No, it means LFTs have poor sensitivity.

In my state you can't even buy LFTs for that reason...
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My daughter got covid about 1 month ago and she tested (LFT) positive two weeks after the infection. She checked online and NHS workers are told not to do LFT for 3 months after an infection - so LFTs seems to give false positives, after you've been infected, i.e. as well as false negatives. Wonder if current LFTs are worse with omicron?
 
FMMM1 said:
My daughter got covid about 1 month ago and she tested (LFT) positive two weeks after the infection. She checked online and NHS workers are told not to do LFT for 3 months after an infection - so LFTs seems to give false positives, after you've been infected
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I don't really consider that to be a "false" positive - the vaccine doesn't protect against the nucleocapsid protein, so you won't have a full adaptive response against it just 2 weeks after infection and antibody based LFTs will continue to test positive months after.
 
Just had a disagreement with someone who believes that the PCR test gets covid confused with flu & that a lot of the positive reuslts are for flu but reported as covid. Citing this as evidence Lab Alert: Changes to CDC RT-PCR for SARS-CoV-2 Testing - ie that the CDC are stopping using it.

But i thought the PCR had high specificity? i dont think it can be 'fooled' into giving a covid positive result because it cant differentiate between covid & flu? that strikes me as scientifically impossible? surely its looking for particular virus?

ISTM the CDC alert is wanting to get lads to use methods that can test forboth at same time? '" mulitplexed methods"

do i have things wrong? Not really well enough for the debate but they spreading it on fb to lots of people i knowso want to do my bit for stopping misinfo
 
JemPD said:
Thanks @Snow Leopard would it be accurate to say it is scientifically impossible for a PCR test to give a positive result for any other virus than the one it is testing for?
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There are false positives, but it is usually due to contamination. The genetic sequences they test for are 100% specific - but no test is 100% perfect - a small number of other things can go wrong.
 
Snow Leopard said:
There are false positives, but it is usually due to contamination. The genetic sequences they test for are 100% specific - but no test is 100% perfect - a small number of other things can go wrong.
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I'm guessing that sampling is the biggest problem - it's pretty difficult to swab your tonsils (gag response) and I think you need to push the swab pretty far up your nostrils --- too much info!
 
I am wondering why people trying to understand the risks posed by omicron do not compare current data in South Africa with previous data on delta from the same demographic which would give a valid comparison between the two viruses in the same population.

I very much hope the answer will be that omicron is more benign for everyones' sakes of course but at the moment in the UK they are saying we have to wait until after Christmas to devise a strategy because we dont know if omicron is less dangerous.

As I understand it, they are saying they think it may be spreading rapidly because it is more immunoevasive, which may be good news on the one hand because it may be less immunogenic as a result and less likely to cause sepsis like responses in patients, so less likely to cause severe reactions where the patients own immune response harms the patient.

On the other hand it is concerning for the prospects of longcovid incidence if, as I suspect wrt my own ME CFIDS, viral immunoevasion promotes viral recurrence as a contributory factor in chronic immune activation.
 
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I'm not sure comparing the severity of Omicron withe the severity of delta in South Africa would work, as I think that would necessitate comparisons between people at different time points, since delta largely preceded Omicron. That would mean by the time Omicron hit the population more of those affected already had some immunity because of previous infection or vaccination, so were more likely to be mildly affected by omicron.
 
Trish said:
I'm not sure comparing the severity of Omicron withe the severity of delta in South Africa would work, as I think that would necessitate comparisons between people at different time points, since delta largely preceded Omicron. That would mean by the time Omicron hit the population more of those affected already had some immunity because of previous infection or vaccination, so were more likely to be mildly affected by omicron.
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Yes but that is likely to apply to other demographics as well. I mean the same population is the best one can do as a control to predict behaviour in other populations surely?
 
The number of deaths as a result of omicron will no be solely down to the severity or otherwise of the virus. It is so infectious that medical staff are becoming sick so they are simply not there to treat patients.

Then there is the sheer number of people infected. If only a small percentage of people become very sick that is still a very large number.

This is not to scare people, it is just infuriating when the "mildness" of the disease is given as a reason for not taking obvious precautions.
 
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