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From what I gather a false positive for an antigen rtPCR is essentially impossible. The primers are extremely specific and can't find something that isn't there

From what I gather a false positive for an antigen rtPCR is essentially impossible. The primers are extremely specific and can't find something that isn't there. A false positive for an antibody test is unlikely to take up hospital resources. They admit people to the hospital for symptoms like dyspnea/hypoxia. Not because the patient tested positive on either the antibody or antigen test. The danger in a false positive for an antibody test IgG or IgM, means gives the patient a false sense of security that they've already gotten the virus and are thus immune in the short to medium future.

logicallee 6y ago
>a false positive for an antigen rtPCR is essentially impossiblee. The primers are extremely specific and can't find something that isn't there. I read somewhere that among the reasons for a false positive would be cross-contamination among samples. Just because the primers find something in the sample, doesn't mean that that something isn't in fact merely a bit of cross-contamination from another, true positive, sample.
- xscott 6y ago
  I was watching this video earlier tonight: https://youtu.be/Vat-PKdQ13A?t=30 https://youtu.be/Vat-PKdQ13A?t=30 That looked like some really sloppy lab technique, and I hope that's not how it is really done in practice. If real tests are done by hand like this, with distractions, open air, and no mask on the technicians, it's easy to imagine false positives.
tinus_hn 6y ago
The South Korea ‘reinfection’ story turned out to be based on false positives.
- acqq 6y ago
  > turned out to be based on false positives. I believed it was based on false negatives in previous PCR tests? It's also a question of understanding what the test actually means. The test doesn't (and can't) claim "this patient is cured" but only "when analyzing this specific sample taken from this patient, no significant trace of virus could be confirmed."
  - tinus_hn 6y ago
    No, the patients were cured but later portions of the virus were again detected. These portions turned out to be inactive. Of course it is possible to define the test in such a way it is 100% effective. This removes the relation to the Covid-19 disease though so then the test is useless.

logicallee 6y ago

>a false positive for an antigen rtPCR is essentially impossiblee. The primers are extremely specific and can't find something that isn't there. I read somewhere that among the reasons for a false positive would be cross-contamination among samples. Just because the primers find something in the sample, doesn't mean that that something isn't in fact merely a bit of cross-contamination from another, true positive, sample.

xscott 6y ago
I was watching this video earlier tonight: https://youtu.be/Vat-PKdQ13A?t=30 https://youtu.be/Vat-PKdQ13A?t=30 That looked like some really sloppy lab technique, and I hope that's not how it is really done in practice. If real tests are done by hand like this, with distractions, open air, and no mask on the technicians, it's easy to imagine false positives.

tinus_hn 6y ago

The South Korea ‘reinfection’ story turned out to be based on false positives.

acqq 6y ago
> turned out to be based on false positives. I believed it was based on false negatives in previous PCR tests? It's also a question of understanding what the test actually means. The test doesn't (and can't) claim "this patient is cured" but only "when analyzing this specific sample taken from this patient, no significant trace of virus could be confirmed."
- tinus_hn 6y ago
  No, the patients were cured but later portions of the virus were again detected. These portions turned out to be inactive. Of course it is possible to define the test in such a way it is 100% effective. This removes the relation to the Covid-19 disease though so then the test is useless.