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False positives and false negatives- how frequent?
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The main Covid test is PCR based and detects viral DNA, and both false positives and false negatives are possible.
False positives
These are due to contamination either during sample collection or processing. A UK study estimated the frequency by looking at published data from PCR tests for other viruses and came up with a median false positive rate of 2.3%.
False negatives
These are due to incorrect sampling, sampling at the wrong stage of the infection or the sample degrading before the test. A recent study of Covid-19 tests estimates a false negative rate of 2-29%. Due to the relatively high rate, it is important not to assume someone is negative from a single test. In some countries, a second sample is taken 24 hours later and the person cleared only if this is negative as well. |
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By (user no longer on site)
over a year ago
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If remembering correctly, the who advised two neg tests before patients were returned/sent to care homes. But this was over-ridden by Hancock, I assume.
It probably would have saved some lives. |
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The PCR test as stated by its inventor who won a Nobel prize for it, should not be used for testing of infectious diseases. It uses amplification and it was confirmed yesterday we are using a CT of 45 which is far too sensitive as it shows up all coronavirus strands months old and not infectious. It does not identify Covid 19 but only coronavirus of which there are many incl common cold. if it is showing false positives at 1.8% that means 80%+ of the so called new cases will be wrong. Its utter madness to shut down parts of the country based on PCR testing. Hancock et al all need sacking. |
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By (user no longer on site)
over a year ago
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Professor Carl Heneghan was giving evidence to the commons select committee on covid yesterday. He pointed out the current test is picking up dead virus from people who had been infected up to 3 months ago, these people though testing positive are neither currently infected or infectious.
His recommendation was to adjust the cycles from the current 45 down to 35. This will then identify those that are actually infectious and then use track and trace on those individuals contacts. |
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"Professor Carl Heneghan was giving evidence to the commons select committee on covid yesterday. He pointed out the current test is picking up dead virus from people who had been infected up to 3 months ago, these people though testing positive are neither currently infected or infectious.
His recommendation was to adjust the cycles from the current 45 down to 35. This will then identify those that are actually infectious and then use track and trace on those individuals contacts. "
35 is still too high according to many so called experts. And how do you propose we identify covid19 rather than coronavirus? As the PCR test cannot distinguish covid. |
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"2-29% is quite the swing. "
Its not easy test to take a sample. Different people do it differently. Also common colds and flu do not produce false positives. The pcr test does produce around 2% false positives but nothing to do with other viruses. The false negatives are more of a problem, hence the search to find a test where sampling is easier than invasive swabbing. |
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"The PCR test as stated by its inventor who won a Nobel prize for it, should not be used for testing of infectious diseases. It uses amplification and it was confirmed yesterday we are using a CT of 45 which is far too sensitive as it shows up all coronavirus strands months old and not infectious. It does not identify Covid 19 but only coronavirus of which there are many incl common cold. if it is showing false positives at 1.8% that means 80%+ of the so called new cases will be wrong. Its utter madness to shut down parts of the country based on PCR testing. Hancock et al all need sacking."
The inventor of the PCR technique who died last year didn't believe that HIV and AIDS were linked, in climate change and ozone depletion but he did believe in astrology. |
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By (user no longer on site)
over a year ago
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"Professor Carl Heneghan was giving evidence to the commons select committee on covid yesterday. He pointed out the current test is picking up dead virus from people who had been infected up to 3 months ago, these people though testing positive are neither currently infected or infectious.
His recommendation was to adjust the cycles from the current 45 down to 35. This will then identify those that are actually infectious and then use track and trace on those individuals contacts.
35 is still too high according to many so called experts. And how do you propose we identify covid19 rather than coronavirus? As the PCR test cannot distinguish covid."
I don't propose anything. I drive a car for a living. |
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"Professor Carl Heneghan was giving evidence to the commons select committee on covid yesterday. He pointed out the current test is picking up dead virus from people who had been infected up to 3 months ago, these people though testing positive are neither currently infected or infectious.
His recommendation was to adjust the cycles from the current 45 down to 35. This will then identify those that are actually infectious and then use track and trace on those individuals contacts.
35 is still too high according to many so called experts. And how do you propose we identify covid19 rather than coronavirus? As the PCR test cannot distinguish covid."
Lol  |
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"
35 is still too high according to many so called experts. And how do you propose we identify covid19 rather than coronavirus?
As the PCR test cannot distinguish covid."
You are aware that that is simply not true, aren't you?  .
The PCR tests used for SARS-COV-2 are solely detecting this specific virus, from detection of its RNA. If you are going to make a bold claim, you would be well advised to cite any credible source.
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"Coronavirus: Common colds 'may account for some reported COVID-19 cases', PHE survey says.
Along with dead virus +'s"
They are reporting the rhinoviruses/common cold could be mistaken for covid nothing about the pcr test though. |
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By (user no longer on site)
over a year ago
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"The main Covid test is PCR based and detects viral DNA, and both false positives and false negatives are possible.
False positives
These are due to contamination either during sample collection or processing. A UK study estimated the frequency by looking at published data from PCR tests for other viruses and came up with a median false positive rate of 2.3%.
False negatives
These are due to incorrect sampling, sampling at the wrong stage of the infection or the sample degrading before the test. A recent study of Covid-19 tests estimates a false negative rate of 2-29%. Due to the relatively high rate, it is important not to assume someone is negative from a single test. In some countries, a second sample is taken 24 hours later and the person cleared only if this is negative as well."
PCR is not a diagnostic test. It's a technique for amplification nuclear material.
|
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"
35 is still too high according to many so called experts. And how do you propose we identify covid19 rather than coronavirus?
As the PCR test cannot distinguish covid.
You are aware that that is simply not true, aren't you? .
The PCR tests used for SARS-COV-2 are solely detecting this specific virus, from detection of its RNA. If you are going to make a bold claim, you would be well advised to cite any credible source.
"
I believe that as you are the one saying its not true, its down to you to cite any credible source that backs up your statement. |
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"The main Covid test is PCR based and detects viral DNA, and both false positives and false negatives are possible.
False positives
These are due to contamination either during sample collection or processing. A UK study estimated the frequency by looking at published data from PCR tests for other viruses and came up with a median false positive rate of 2.3%.
False negatives
These are due to incorrect sampling, sampling at the wrong stage of the infection or the sample degrading before the test. A recent study of Covid-19 tests estimates a false negative rate of 2-29%. Due to the relatively high rate, it is important not to assume someone is negative from a single test. In some countries, a second sample is taken 24 hours later and the person cleared only if this is negative as well.
PCR is not a diagnostic test. It's a technique for amplification nuclear material.
"
Indeed it is. And contrary to what is bandied about, the test is not directly picking up the virus. PCR amplifies strands of DNA. Covid 19 is an RNA virus. Hence a DNA copy of its genetic material first needs to be produced before the PCR process can amplify. This step can also be error prone due to inaccuracy in the reverse transcription process. But noooobody even mentions this!
|
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"The main Covid test is PCR based and detects viral DNA, and both false positives and false negatives are possible.
False positives
These are due to contamination either during sample collection or processing. A UK study estimated the frequency by looking at published data from PCR tests for other viruses and came up with a median false positive rate of 2.3%.
False negatives
These are due to incorrect sampling, sampling at the wrong stage of the infection or the sample degrading before the test. A recent study of Covid-19 tests estimates a false negative rate of 2-29%. Due to the relatively high rate, it is important not to assume someone is negative from a single test. In some countries, a second sample is taken 24 hours later and the person cleared only if this is negative as well.
PCR is not a diagnostic test. It's a technique for amplification nuclear material.
Indeed it is. And contrary to what is bandied about, the test is not directly picking up the virus. PCR amplifies strands of DNA. Covid 19 is an RNA virus. Hence a DNA copy of its genetic material first needs to be produced before the PCR process can amplify. This step can also be error prone due to inaccuracy in the reverse transcription process. But noooobody even mentions this!
"
Shhh don't mention the leprechauns either we don't want people to know |
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"The main Covid test is PCR based and detects viral DNA, and both false positives and false negatives are possible.
False positives
These are due to contamination either during sample collection or processing. A UK study estimated the frequency by looking at published data from PCR tests for other viruses and came up with a median false positive rate of 2.3%.
False negatives
These are due to incorrect sampling, sampling at the wrong stage of the infection or the sample degrading before the test. A recent study of Covid-19 tests estimates a false negative rate of 2-29%. Due to the relatively high rate, it is important not to assume someone is negative from a single test. In some countries, a second sample is taken 24 hours later and the person cleared only if this is negative as well.
PCR is not a diagnostic test. It's a technique for amplification nuclear material.
Indeed it is. And contrary to what is bandied about, the test is not directly picking up the virus. PCR amplifies strands of DNA. Covid 19 is an RNA virus. Hence a DNA copy of its genetic material first needs to be produced before the PCR process can amplify. This step can also be error prone due to inaccuracy in the reverse transcription process. But noooobody even mentions this!
Shhh don't mention the leprechauns either we don't want people to know"
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