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[Breaking News] A ‘negative’ coronavirus test result doesn’t always mean you aren’t infected

Jamie Sparks
(@jamie-sparks)
Trusted Member

So you have a cough and fever, and you just got test results back for the novel coronavirus: Negative!

But wait a second. Your doctor may still caution you to act like you could have it. Stay home. Self-isolate. Don’t go visit your parents.

What’s going on?

The clamor for long-delayed coronavirus testing is teaching a basic lesson about how all medical tests work: No test is 100 percent accurate. Some test results may incorrectly say that a person has a condition, but they don’t. That’s a false positive. Other tests may incorrectly say someone doesn’t have a condition, but they do. That’s a false negative, and for covid-19, the illness caused by the coronavirus, at this stage of the outbreak, experts are more worried about this type of inaccuracy.

When a new test is rapidly created and deployed, its accuracy is often not fully known. The test is developed under controlled lab conditions, but it is used on samples taken, transported and performed by people in the real world — all of which increase the likelihood of errors.

The novel coronavirus tests use a swab to take a sample from the back of a person’s nose or throat. The swab is then transported to a lab that isolates and detects genetic material from the coronavirus.

Any medical test has two important qualities: sensitivity and specificity. The tests are proven to be “sensitive” in laboratory conditions — in this case, a technical measure of the smallest amount of virus they can detect. The tests must also be “specific” — for example, ensuring they do not mistake other pathogens, such as the common cold coronaviruses, for the new SARS-CoV-2.

 

The genetic tests being used are typically very sensitive and specific under lab conditions, but in the real world, how the swab was done and the stage of illness the person was in can make a big difference. To complicate the situation, there isn’t one test — many different tests are now being used by commercial laboratories, hospital labs and the Centers for Disease Control and Prevention. And the interpretation of the results will depend on not just the test, but other external factors, such as how widely the disease has already spread and laboratory practices.

“If it’s positive … you absolutely can make a [clinical] decision. If it’s negative, you may be early on in the infection and the viral load may be so low you don’t get it,” Anthony S. Fauci, the director of the National Institute for Allergy and Infectious Disease, said in a Q&A with JAMA.

A Cleveland Clinic researcher said the test developed by his hospital system is highly sensitive and specific in the laboratory, returning no false-negative results. But he acknowledged those numbers won’t exactly represent how the test will perform in the real world. Another researcher said anecdotal reports peg the genetic coronavirus tests being used in the United States at about 85 percent sensitive. That means that for someone who has the virus, there’s a 15 percent chance they test negative. A critical-care blog, EMCrit, estimated that the genetic tests are about 75 percent sensitive and suggests that a single negative swab doesn’t rule out the disease.

Documentation for the test approved for New York’s state lab explains the possibility of a false positive or false negative, emphasizing that a negative test doesn’t rule out infection.

“A negative result does not rule out COVID-19 and should not be used as the sole basis for treatment or patient management decisions,” according to the fact sheet for health-care providers. “When diagnostic testing is negative, the possibility of a false negative result should be considered in the context of a patient’s recent exposures and the presence of clinical signs and symptoms consistent with COVID-19."

People who test negative may find it confusing and hard to believe the result.

 

Laura Frazelle, a 34-year-old violinist from Virginia, found out her test was negative after a week in the hospital and 10 days after being tested. She was grateful to be home, but even more worried about covid-19 given the severity of the unspecified illness she had just survived.

″My final diagnosis was pneumonia in both lungs due to an unspecified infectious organism,” Frazelle said. “Yes, it’s a pretty big coincidence that I happened to be hospitalized for an infection that has all of the symptoms of a current global pandemic.”

Read rest of the Story Here on Washington Post

Quote
Topic starter Posted : 29/04/2020 5:18 pm
WisdomUpdates
(@wisdomupdates)
Eminent Member

I have always wondered this, but now it has been confirmed by medical experts. So, basically, if you have symptoms, nomatter how little and mild, then isolate yourself and try to protect others around you by assuming that you may have it.

The same advice as above, for those who have been reasonably exposed.

...Thank you for bringing this to our knowledge.

ReplyQuote
Posted : 29/04/2020 5:32 pm
Jamie Sparks
(@jamie-sparks)
Trusted Member

@wisdomupdates You are welcome.

It was simply that nothing is always 100% accurate at all times. Most especially when it comes to man-made, man operated and administered technologies, which was made at a time like this with limited prior deployment to the field.

ReplyQuote
Topic starter Posted : 30/04/2020 12:07 pm
Michi
(@michelle)
Estimable Member

I guess the rule would be to err on the side of caution, always.  Tough when people are losing their jobs everywhere and there is no end in sight.

ReplyQuote
Posted : 01/05/2020 2:43 pm
MacGenesis
(@macgenesis)
Trusted Member

@michelle

Yes. It's far safer to err on the side of caution.

ReplyQuote
Posted : 01/05/2020 6:55 pm
Jamie Sparks
(@jamie-sparks)
Trusted Member
Posted by: @michelle

I guess the rule would be to err on the side of caution, always

Well said. I support that

ReplyQuote
Topic starter Posted : 03/05/2020 2:59 pm
Michi liked
Blake Griffey
(@blakegriffey)
Member Moderator

Thanks for sharing! It is good to be reminded of this. This is true of all tests, that negatives and positives can be false. It is never bad to be too careful right now!

ReplyQuote
Posted : 06/05/2020 5:18 pm
Max
 Max
(@max)
Eminent Member

Wow this is a real eye-opener. Compound that with the fact that symptoms only start showing 14 days after infection. Plus the possibility of faulty testing equipment really puts into perspective the validity of the tests carried out in recent months

ReplyQuote
Posted : 14/05/2020 1:39 am
Joel
 Joel
(@joel)
Eminent Member

What worries me more is the speed at which the supposed vaccines were created and are being touted to enter the market very soon. People want a cure so bad they will accept anything and that's where the problem lies.

ReplyQuote
Posted : 14/05/2020 9:34 am
PolyaDAymn
(@polyadaymn)
New Member

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Posted : 03/02/2021 6:47 am
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