False Negatives Raise More Questions About Virus T
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The first study found that Abbott’s ID NOW machine missed at least one-third of positive cases detected with a rival test, and as many as 48% when using the currently recommended dry nasal swabs, according to the report on BioRxiv
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The second analysis, published in the Annals of Internal Medicine and authored by Johns Hopkins researchers, analyzed seven previously-published studies evaluating 1,330 patient samples and focused on a group of widely-used Covid-19 diagnostic tests known as “polymerase chain reaction” tests. It suggested that false negatives are especially likely before the onset of symptoms, such as when a patient is tested soon after exposure to the virus.
When patients were tested immediately after infection, typically before symptoms occur, the false-negative rate was 100%. On the first day of symptoms, the false-negative rate was 38%. After three days of symptoms, false-negatives dropped to 20%. The rate began getting worse after five days, suggesting a narrow window for the most accurate results.
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https://www.bloomberg.com/news/articles/2020-...f=5sXCNkPB