![]() You may have heard rumors about something called the "cycle threshold" being changed. This World Health Organization (WHO) notice did not change the criteria for a positive COVID-19 test. Have the criteria for a positive PCR test changed, making PCR tests report fewer COVID-19 cases? "Comparing these genetic sequences means we can avoid cross-reactivity," says Dr. That way, they ensured the PCR test only picked up a piece unique to SARS-CoV-2 and not another coronavirus or influenza. Researchers also looked through large databases of viral genetic sequences – the building blocks of a virus.The PCR test reported negative on all of them, which makes sense. These clinical samples included known results of influenza and other common viruses. Our researchers took clinical samples from before Nebraska had community spread of COVID-19 and ran the samples through the test.To ensure specificity, they tested clinical samples and also used databases of genetic sequences. Broadhurst, microbiologist Paul Fey, PhD, microbiology fellow Hannah Creager, PhD, and other experts worked together to ensure a trustworthy test. That includes demonstrating the specificity of the test to exclude anything that may cause a false positive."ĭr. Broadhurst explains, "At the beginning of the pandemic, we went through a very rigorous process. The Nebraska Medicine PCR test has been extensively vetted with multiple ways of validation.ĭr. And now many PCR tests can detect both SARS-CoV-2 and influenza at the same time." How do we know COVID-19 cases aren't actually influenza?Įvery PCR test must be validated, meaning checked for its sensitivity and specificity. "It is the most accurate testing modality that we have. "PCR tests are the gold standard for detecting SARS-CoV-2," says Dr. PCR tests are more accurate than antigen tests. Which is a more accurate test for detecting COVID-19 – PCR or antigen? So you'd have to get a second test to see if it's something elseīut a multiplexed test can determine both viruses at the same time, saving the patient an uncomfortable nasal swab. Negative means you likely don't have COVID-19 – but you may have influenza or another coronavirus.Positive means the test found SARS-CoV-2, the virus that causes COVID-19.The CDC is choosing to use a multiplexed PCR test rather than the original PCR test to save time.Īll PCR tests give either a positive or negative result for each virus it detects. It correctly identified SARS-CoV-2 out of all of these samples. Broadhurst says, "The PCR test is validated against many different coronaviruses and common respiratory viruses, including influenza so that it would not give false-positive results." Meaning, researchers subjected the test to many different samples to see if it would give the wrong result. Basically, specificity means that the test is designed to only detect one type of virus. "The original test could detect the presence of SARS-CoV-2 with very high specificity," – meaning the test does its job very well.Ī PCR test is an excellent identifier of COVID-19 cases, because of something called specificity. "The reported numbers were based on highly accurate laboratory tests," says Dr. "We can be very confident that a positive result from a PCR test represents a true case of SARS-CoV-2 because of how these tests were designed." Did previous PCR tests confuse COVID-19 cases for influenza cases? "Just because the original test wasn't built to detect influenza doesn't mean that it wasn't accurately reporting results," Dr. The PCR test was extraordinarily accurate in identifying the right virus: SARS-CoV-2. PCR tests are more accurate and reliable than antigen testsĭoes the recall mean the original CDC PCR test gave inaccurate results?. ![]()
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