Questions tagged [pcr]

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False positives of PCR test on symptomatic individuals

On this website, I see that less than 2% of people who don’t have Covid-19 test positive with a PCR test. What happens to this percentage when we only consider symptomatic people? So my question is: ...
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Why are COVID nucleic acid tests sometimes reported with non-integer CT values?

I saw a positive COVID test, and the CT value was not reported as an integer value. Instead, it was reported with two decimal point precision. I expected the CT value to be the number of PCR cycles. I ...
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Help interpreting PCR lab results [closed]

Started isolating after my brother, who I live with tested positive, and four days later I was also testing positive (making it likely he transmitted it to me). I did a PCR test and the lab returned ...
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Can a RT-PCR test claim 100% sensitivity and specificity?

A recent RT-PCR test for SARS-CoV-2 from a private laboratory lists the test's sensitivity and specificity as 100%. The test certificate lists this next to the result: Ref. value/Норма Negative (...
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How long it will take for a RT-PCR test CT value to go to from 27 to 35?

A RT-PCR test came positive and the CT value is 27, which means apparently a low contagion level. But is there a way to estimate when (in average) it could go til 35 (the cutoff)? The graph from here ...
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2 votes
2 answers
129 views

Antigen vs PCR test

In the Czech Republic there is now mandatory testing for factory employees. Anecdotally I am now being told by people I am acquainted with, who run medium sized firms here, that their employees are ...
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3 votes
1 answer
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Do presymptomatic people test PCR-positive

I know that RT-PCR testing can detect coronavirus in symptomatic and asymptomatic carriers. I was wondering whether a presymptomatic carrier (I don't know if the terminology is correct, but I mean ...
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Who's RNA does the rRT-PCR test for SARS-CoV-2 target?

The official guide for laboratory testing for coronavirus disease in suspected human cases by the WHO explains the procedure for testing a sample. On page two it states that the test is based on ...
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2 votes
1 answer
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False Positive PCR - COVID-19 and possible reinfection when antibodies value is +7.0

A friend of mine was detected COVID-19 positive through PCR one month back. He was asymptotic as per doctors and had no symptoms. He quarantined himself and increased his intake of water. After 1 ...
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5 votes
2 answers
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Has China announced any results from their massive (new) COVID-19 testing program in Wuhan?

About 10 days ago China announced a plan to test the entire population (~11 million) of Wuhan. And more recently they've announced testing over 1 million per day in the city. But have any results been ...
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Why does CDC's RT-PCR protocol for Covid-19 use the N gene, but the Charite one the E gene and RdRp?

The Charite protocol mentioned among other things that Of note, the N gene assay also performed well but was not subjected to intensive further validation because it was slightly less sensitive. ...
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How often is a Ct of 30 (or more) using the Charité protocol a false positive for Covid-19?

A French case report that has received widespread media attention suggests (actually stated in pretty strong terms in the paper) that Covid-19 was already spreading in France in December 2019. (In ...
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Having tested positive for COVID-19, will future tests be positive?

The World Health Organization indicates the COVID-19 genome is detected in assays. Once a patient tests positive, is there any reason not to expect that future instances of the same assay will result ...
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6 votes
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117 views

How do they test COVID-19 in drive-thru labs?

I've read that SARS-CoV-2 virus which causes COVID-19 disease can be tested with RT-qPCR.[1] It seems a somewhat lengthy procedure. Then it's unclear to me: how do they test the virus in drive-...
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