Questions tagged [pcr]

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What is the principle behind PCR/NAAT test, in the context of HIV, especially compared to antigen/antibody test?

So here's my limited understanding of how viral infections work. Some virus enters the body and causes an infection. The virus then begins to replicate itself. It takes some time for there to be ...
Philip's user avatar
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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: ...
Riemann's user avatar
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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 ...
user11235's user avatar
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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 ...
Pistachio's user avatar
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8 votes
1 answer
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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 (...
DK2AX's user avatar
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1 answer
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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 ...
Vega's user avatar
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2 votes
2 answers
134 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 ...
Frank's user avatar
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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 ...
Frotaur's user avatar
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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 ...
bitmask's user avatar
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2 votes
1 answer
128 views

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 ...
Badddy's user avatar
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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 ...
Fizz's user avatar
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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. ...
Fizz's user avatar
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2 votes
1 answer
60 views

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 ...
Fizz's user avatar
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1 vote
1 answer
90 views

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 ...
gatorback's user avatar
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6 votes
1 answer
118 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-...
Andriy Makukha's user avatar