1/ Are there really false-positives from COVID tests? If so, how is it possible for a test to pick up something that is not there?

A: Yep, they exist. Image Credit: Jernej Furman, focusonmore.com
2/ Two types of tests are commonly used to identify an active #COVID19 infection, & both of them can occasionally lead to a “false-positive” result, or a positive test result when there is actually no infection present.
3/ The two types of tests are:
1. PCR tests 🧬, which detect itty bitty pieces of the virus’ genetic material, &
2. Antigen tests 🦠, which detect signature proteins on the outside of the virus. (Note: Don’t confuse antigen with antibody tests 🩸 ! That's different.)
4/ 🧬🧬A PCR test works using a chemical reaction that matches genetic material collected in the sample to two fragments of genetic code that are totally unique to SARS-CoV-2.
5/ If there’s no match, the test is negative. If there’s a match on one fragment but not the other, the test is inconclusive & will usually be repeated, & if there is a match on both fragments, the test is positive.
6/ Scientists think that false-positives in PCR tests happen most often because the bits of genetic code we are matching TO are very small fragments. Small remnants of the virus in the sample might match, even though they are not whole viruses & couldn’t infect anyone.
7/ An infected person is likely no longer able to get others sick about 10-14 days after their first symptoms appear, but they may still have little bits of inactive viral material in their body for quite some time.
8/ We've heard reports of people with positive PCR tests *months* after their symptoms have abated (shout out to Lu in Italy! Hang in there). This is likely due to inactive viral material still hanging around in the body after infection.
9/ 🦠🦠Antigen tests give a positive result when they detect a particular protein on the surface of the virus, like a fingerprint. Antigen tests have some major advantages, including being fast & cheap. If you’ve ever had a rapid strep test, you’ve had an antigen test.
10/ Antigen tests can return false-positives if they find a similar protein, if the sample is handled incorrectly, or if something goes wrong with the test chemicals.

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More from @DearPandemic

13 Oct
1/ Q: What do you think of the idea of “focused protection” or “shielding” the vulnerable so that everyone else can get on with normal life?

A: We *wish* it were this easy, but sadly it’s not.
2/ While this approach sounds appealing on the surface, the deeper you dig the more the argument folds in on itself.

Let me explain...
3/ 👉The death and hospitalization toll even in under 65s would be staggering

👉No consideration of waning immunity and re-infection

👉No mention of impact of “Long Covid” for millions infected

👉Cordoning off of a large percentage of the population is not feasible
Read 31 tweets
13 Oct
1/ What do we do when college-age children come home at #Thanksgiving? Should they come home?

A: “Come Home & Stay Home” or “Don’t Come Home” are your best options. Coming home just for the Thanksgiving holiday & then returning to campus is *not* a good plan. p/c: Dan Renzetti
2/ Some of your options are clearly better than others from a #COVID safety perspective. Before we go through those options, we want to highlight a common mental bias to which we are all susceptible: We underestimate the risk of getting COVID from people we know and love.
3/ Dr. Birx mentioned this in a recent speech, as she noted increasing case counts that are likely driven by small gatherings of family. “We take down our guard when we are with people we know... & we assume if we know you, you couldn’t have COVID.”
bit.ly/2H4ykJK
Read 12 tweets
11 Oct
1/ Q: How can I boost my immune system?

A: Today we focus on the importance of sleep health as an evidence-based strategy for improving your immune system during the COVID-19 pandemic.
2/ * Long-term sleep deficiency is associated with a range of co-morbidities (type 2 diabetes, cardiovascular disease, dementia) that put you at higher susceptibility & more severe outcomes of COVID-19.
3/ You can reduce your risk factors for these comorbidities by practicing good health behaviors, such as prioritizing sleep, exercise, and a diet rich in fruits and vegetables) Even little changes in lifestyle can add up over time.
Read 7 tweets
6 Oct
1/ Q: Is it true that #Sweden has gotten to herd immunity without lockdown? Should we all be doing what they are doing?

A: No, Sweden has not reached herd immunity, nor have they fared well economically or with respect to COVID-19 mortality.
2/ While there has been a fascination with being Sweden during this pandemic, there are many misconceptions about their experience that are worth clearing up:
2/ *Myth 1*: Sweden didn’t place restrictions on activities due to #COVID19

*Reality*: While it’s true there was no nationwide mandatory lockdowns as in Spain, Italy, the UK & US, Sweden did have a “lockdown lite."
Read 14 tweets
5 Oct
1/ Q. What's the update with COVID-19-sniffing dogs?

A. The Helsinki-Vantaa airport welcomed COVID-19-sniffing dogs to their staff last week, hoping to use their keen sense of smell to detect COVID-19 positive patients up to 5 days before symptoms appear. bit.ly/33t3Utg Photo Credit: Elias Castillo
2/ Here's how the airport testing works: Prospective passengers rub a wipe against their neck to pick up some sweat, & then drop the wipe in a cup. While inside an isolated booth, the trained pup takes a whiff of the cup & provides a positive or negative verdict.
3/ If the dog sniffs a positive, he creates an audible signal. Then, the passenger is informed & sent to the airport's health information area. This is much quicker & less invasive than a nasal swab.
Read 8 tweets
4 Oct
1/ Q: What do epidemiologists think about Joe Biden & Mike Pence (& other national leaders) testing negative for COVID on Friday?

A: A negative test result does NOT mean that Mr. Pence and Mr. Biden are COVID-free… even if that happens to be really inconvenient for them.
2/ Everyone who has been near the President in the last week (or who has been around anyone else with #COVID19 for that matter) should self-quarantine for 14 days following the last exposure. That means Joe Biden & Mike Pence should stay home.
3/ This is the official guidance from the @CDCgov, @WHO, & leading institutions across medicine & public health.

It’s not politics, it’s just science.
Read 9 tweets

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