Covid-19 Tests?

Discussion in 'Biology & Genetics' started by KUMAR5, Jan 6, 2022.

  1. KUMAR5 Valued Senior Member

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    Hello.
    Greetings?

    I have a confusion:-

    How RT-PCR or other rapid tests meant for Covid 19 also come positive in case of infection from its variants say Delta or Omnicron?

    Can it mean these tests simply detect Corona family virus but not specifically to Covid 19 virus for which genome screening will also be needed to ensure soecific virus screening? Not sure, during epidemic or pademic, it is taken as granted that it should be the same soecific virus but still not for sure. Many symptoms can be similar in same virus family infection so can confuse.

    One common cold virus is also classified under this family.

    Best wishes.
     
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  3. exchemist Valued Senior Member

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    Obviously not or it would not work, would it? The whole point of the test is to discriminate between SARS-CoV-2 and other viruses. Do you think these people are all incompetent?
     
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  5. KUMAR5 Valued Senior Member

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    Sorry, it is just presumption. How does then Omnicroon infection come positive in these tests meant for Covid 19?
    I think all or many virus in corona family are just variants of corona virus.
    I think there is always a disclaimer in every RT OCR test that this test can also pick other viruseems(will quote exact later).
     
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  7. billvon Valued Senior Member

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    Because they detect a set of antigens that did not change significantly between the last two variants.
    No.
     
  8. KUMAR5 Valued Senior Member

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    Does it mean these tests are not absolute to soecifuc type of covid 19 virus?.

    Confusion is also due to that there are so many variations in getting symptoms and recovery. Most get upper respiratory symptoms other lower. Many get fever other not. Many recover at home by minor treatments others not even by aggressibve treatments in hospital. Few recover in say 10 days other in 3 days and few other even in months. Vaccine effect may also show variable effects. Why can't it be due to different variants vin this famiky in actual?
     
  9. billvon Valued Senior Member

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    "Quick" (antigen) tests recognize a set of antigens (proteins) from the virus. This set is chosen to be unique to that virus.

    Viruses contain hundreds to thousands of antigens, so it is possible that a mutation will change some of those antigens. However, it is unlikely to change all the antigens chosen for the set used in the test.
    It can be. However, more likely it is due to different people's immune systems reacting differently to the virus (and their underlying state of health when they get it.)
     
  10. KUMAR5 Valued Senior Member

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    Thanks.
    Still, it suggests it is a gross test but not exaxt test to a specific variant. What about RT PCR test? Is it also baaed on antigen type similarly?

    Actualky. Here in one city Apx 10000 cases are tested positive for Covid 19 but hardly 300 for omnicron. However unofficially it is estimated that about 80% of these 10000 are Omnicron infected because doing genome testing of all 10000 us neither practical nor useful. Spread, Symptoms and recovery of most is also matched to Omnicron infection but they simply got tests positive for Covid 19.

    Yes I think type of immune system, quakity and quantity of virus can matter.
     
  11. billvon Valued Senior Member

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    So the difference there is that antigen tests look for antigens; PCR tests look for the RNA of the virus itself. (PCR refers to the amplification of the RNA/DNA so there's enough to use elecrophoresis to get a genetic "signature" of the virus RNA.)

    Thus PCR is somewhat safer in terms of not missing a variant, because you can look at the RNA signature and say "you know that doesn't look EXACTLY like our reference test but it's very close so it must be COVID."
    Well, if they are not specifically testing for omicron they won't see it. So is that 99,700 tests that were negative for Omicron, or is it just that they got 100,000 positives for COVD, then tested 600 of those for omicron?
     
  12. KUMAR5 Valued Senior Member

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    Here RT PCR test is done only for COVID 19. However they pick up few minor cases out of these and do some genone screening to ensure it is omricron or not. But unofficially they assume 80% out of total positive for covid 19 are omnicron infected. But it can not be taken as sure unless all 10000(not 100000) are screened by geñone testing.
     
  13. exchemist Valued Senior Member

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    The spelling is O M I C R O N.
     
  14. KUMAR5 Valued Senior Member

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    Sorry and thanks. It is bit new and very confusing

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    Still many things need to be cleared on it. Does it really come under RT PCR mesnt for Covid or some other test is needed? Antibody side..if it forms antibodies vand if previously formed antibodies by natural infection by Covid 19 or Delta or by vaccine work for it or not?
    One my close relative infected by Covud 19 before 30 days and fully recovered befire 20 days, shown positive RT PCR today. It is assumed that it is Omicron. Double vaccinated. Does it not suggest yhat formed antibodues are not effective against Omicron?
     
  15. billvon Valued Senior Member

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    Well, no. Statistically you can get to whatever level of certainty you want by taking a (small) sample of the total tests. You don't have to test everyone.
     
  16. KUMAR5 Valued Senior Member

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    Yes right but when all three i.e. Covid 19, Delta and Omicron exist in more or less proportion at a time and confuse in RT PCR test, how can we said say for sure what one got and which is to be treated? Level of symptoms also confuse because at some stage these resemble with other but at other stage not.
    Anyway, can RT PCR test meant for Covid 19 virus also pick some other virus in Corona family say eg for common cold virus of this family?
     
  17. billvon Valued Senior Member

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    There is no difference in treatment between the strains. Knowing which strain it is is useful information for research, but not for treatment - so you don't have to know everyone's actual strain.
    Nope. Different signature.
     
  18. KUMAR5 Valued Senior Member

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    Sorry, some difference is there in treatments. Antibody cocktail is saud to be effective for vovid 19 and delta and given but not to Omicron patient's. Morever there are other differencee since formers have lower and other systemic effect and mire severe wheress later just show upper respiratory tract imoact snd less severity. So the different treatment accordingly.

    How then a disclaimer is given on every RT OCR report that it can also pick some other virus?
     
  19. KUMAR5 Valued Senior Member

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    Since test for Omicron, Covid 19 and Delta is mostly done by RT PCR or Rapid Antigen origionalky meant for Covid 19, is there not a big confusion in severity snd fatality data due to mix of these three? How can we be very sure, ehich variant has caused what? As such many cases of one may be attributed to other. So should there not be seorate tests and seorate datas of each variant to know exact position?
     
  20. billvon Valued Senior Member

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    Nope.
    By testing subsets of the PCR tests for what strain they are.
    Nope, not practical. You will never get 100% of the people tested. Thus they are targeted to at-risk and symptomatic people, and (when there are enough tests) spot testing.
     
  21. KUMAR5 Valued Senior Member

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    Does it mean that whatever data of hospitalization or death published recently from C ovid can not be solely attributed to 'suffered from Omicron' for sure?
     
    Last edited: Jan 25, 2022
  22. exchemist Valued Senior Member

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    No, not at all. As billvon has just explained, By testing subsets you can get a good estimate of the proportion of hospital admissions with Covid can be attributed to each variant.
     
  23. billvon Valued Senior Member

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    No, that's not what it means.

    Do you understand statistics?
     

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