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How COVID-19 testing works and why Minnesota’s capacity to do it is limited

Medical personnel swabbing an employee’s nose
REUTERS/Brian Snyder
Medical personnel swabbing an employee’s nose at a drive-through testing site for coronavirus for employees at UW Medical Center Northwest in Seattle, Washington.

There have been a lot of questions about testing for COVID-19 in the ten days since Minnesota got its first confirmed case of the virus.

The biggest one is why there aren’t more tests available. The Centers for Disease Control has been under fire for not ramping up the distribution of tests to state and local health departments, forcing front line workers to ration them.

But even with a bigger supply of test materials, labs’ capacity to do the tests once they receive them is also a limiting factor: in Minnesota, only the state Department of Health’s lab could test in the first few days of the outbreak in the state. Now, the Mayo Clinic and several commercial labs are processing kits to help, too.

Here’s how the testing process works.

Who should get tested

As of Saturday, the Minnesota Department of Health was recommending people who meet certain criteria, like having traveled somewhere with a high number of COVID-19 cases or having exposure to a confirmed case, be prioritized. But the department said Saturday it was giving health care providers some discretion in who to test and not test.

Symptoms of COVID-19 include fever, cough and shortness of breath, which are likely to develop between 2 and 14 days after exposure to the virus, according to the CDC. MDH is not currently recommending people who are not displaying symptoms of COVID-19 be tested, and has asked medical providers to test for other respiratory illnesses, like flu, before testing for COVID-19.

For those wondering if they need a test, it’s best to call your medical provider to get a testing referral — visiting a health care setting with potential COVID-19 symptoms can expose others to the virus.

Getting swabbed

Once you have a referral, you can use a drive-up or other testing site. M Health Fairview, the Mayo Clinic and other facilities are offering this service.

In most places, medical professionals collect two swabs, one called a nasopharyngeal swab, which goes through the nose and into the pharynx, and another, a throat swab, said Dr. Mark Schleiss, a professor of pediatrics in the University of Minnesota Medical School.

Those samples get sent to a lab, where it goes through a process called detect reverse transcriptase PCR (the PCR stands for polymerase chain reaction).

“[It’s a] test that’s specifically looking to detect the RNA of the coronavirus, basically the genes of the virus,” said Louis Mansky, the director of the Institute for Molecular Virology at the University of Minnesota.

In the lab

The lab worker puts the sample in a solution and extracts all its RNA.This likely includes RNA from cells from the person’s nose and throat as well as any virus RNA present.

Then comes reverse transcription, which basically involves making a DNA copy from the RNA.

Since scientists very quickly sequenced the coronavirus’ RNA, they know what to look for. They use a device called a thermocycler, which, among other things, changes temperatures to amplify the target that represents a part of the coronavirus’ RNA, Mansky said.

Lab workers use things called fluors — little tags put on DNA and RNA molecules — to detect the virus, Schleiss said.

“If you get them excited, they will glow … it will release the fluors, as the abbreviation implies, it is a fluorescent signal, and the machine can read that,” he said. That signals a positive case of COVID-19 .

Though more commercial labs are becoming available to run tests in Minnesota, lab capacity is limited.

“Even with more laboratories [available], the challenge is that all those laboratories are needing to use the same elemental components for their tests, so that puts pressure on the entire system within Minnesota, within the country, across the globe,” said MDH Infectious Disease Director Kris Ehresmann said in a weekend press call. So that becomes the challenge, making sure that everyone still has the necessary components they need to be able to test.”

In some cases, COVID-19 test results are being turned around in 24 hours. An MPR producer who was tested in Minnesota last week said she learned of her negative result within two days.

Comments (36)

  1. Submitted by Randy Purchase on 03/16/2020 - 10:53 am.

    Good job. Vary informative.

  2. Submitted by Pat Berg since 2011 on 03/16/2020 - 11:10 am.

    I’ve read descriptions of the test and how it is run, but so far I don’t recall seeing anything on it’s rate of either false positives or false negatives, and whether it tends to skew towards one or the other.

    Greta, is this something you could fill in?

  3. Submitted by joe smith on 03/16/2020 - 11:35 am.

    When the FDA got involved with overseeing and approving CDC testing kits, 2 huge cumbersome Federal agencies, nothing good was going to happen. After the H1N1 flu virus, which killed an estimated 500k+ Worldwide , you think we would have become more nimble, didn’t happen. The CDC ran the sole laboratory for testing for Coronavirus until 1 week ago. Getting more labs and test kits will depend on the innovation of the free market not the FDA collaborating with CDC.

    • Submitted by Henk Tobias on 03/16/2020 - 12:42 pm.


      We did get more nibble, President Obama created something called the NSC directorate for global health and security and bio-defense that was tasked with dealing with pandemics. Donald disbanded it in 2018.

      Early on there was a test approved by the World Health Organization. All the FDA had to do was approve it. I guess that was too much to ask, instead the Trump Administration instructed the CDC to work with the private sector to come up with their own test. It turned out to be a failure. Once they got it working they sent a bunch of them to California without critical pieces of the tests so those were useless as well.

      Government agencies work quite well when they have competent leaders running them. Right now we don’t have that.

      • Submitted by Gretchen Roberts on 03/16/2020 - 01:22 pm.

        your response was not factual and instead quite biased. Government agencies, in my opinion don’t work well, whether they have competent leaders or not, just look at the VA. “Donald” did not disband it and in fact was not even aware of it – as he stated in an interview – someone , somewhere in the bureaucracy did. I realize it is easier to blame Trump for everything than to actually come up with something that is factual and helpful.

        • Submitted by Pat Berg since 2011 on 03/16/2020 - 02:18 pm.

          Donald J. Trump, November 8, 2013:

          “Leadership: Whatever happens, you’re responsible. If it doesn’t happen, you’re responsible.”

        • Submitted by James Miller on 03/16/2020 - 03:00 pm.

          Gretchen, The Trump administration is solely responsible for eliminating the White House’s National Security Council Directorate for Global Health Security and Biodefense. There’s no political posturing here; it’s a binary act.

        • Submitted by Pat Terry on 03/16/2020 - 05:03 pm.

          What you have just said is completely false. What Henk said is completely accurate. It was’t the bureaucracy that did it – it was Trump’s political appointee. Henk’s “bias” is for the truth over easily provable lies.

          And it does make a difference who is in charge. That difference is not whether its a Republican or Democrat. Republican governors like Mike DeWine have been great. No, the difference is having a competent and honest leader in the White House. And we don’t have that now. We have a man who has gone out day after day and provided false information. More people are going to die because of Trump’s incompetence.

          And for those who are more worried about the economy than all the people who will die, you can blame Trump for that too. A better response would help mitigate the damage. But that is what we get by electing an actor who pretends to be a successful businessman, but who, in reality, has squandered a huge inheritance and failed in nearly every business he has attempted to run. He is now doing to America what he did to all the people who worked for him.

          • Submitted by Bob Barnes on 03/16/2020 - 08:08 pm.

            Actually Trump was early and proactive .. he stopped travel from China 6+ weeks ago. Bolton got rid of the NSC council but most of the people on it are still working at the White House. So your claims that Trump disbanded this or that and caused more people to die is completely false and something you simply can never prove. The testing kids from overseas were shown to have a nearly 50% false negative rates so they were worthless.

            Nothing Trump has done has been bad for the response to the virus. He’s done a lot of dumb things but this wasn’t one of them. As this article points out, even if we had millions of test kits.. we couldn’t have processed them due to lab shortages. Again, not Trump’s fault.. that would be more on Obama because of the changes he made if memory serves.

        • Submitted by Paul Udstrand on 03/17/2020 - 08:45 am.

          Gretchen, other countries have governments that work, it’s “government” that’s the problem, it’s OUR government and it’s current lack of true leadership. The difference between the US and Europe isn’t “government” vs. no government. The difference is that S. Korea, Europe, etc. have governments with pandemic response teams in place that were able to plan and direct more organized responses. Our government is run by a buffoon who told people he’s a genius who could’ve been a M.D. and that our response was “perfect”, and that this virus would magically disappear this summer. All of that a year AFTER firing the team that would have recognized, planned, and directed our response to a novel deadly virus.

      • Submitted by Bob Barnes on 03/16/2020 - 04:01 pm.

        Bolton disbanded that NSC unit but most of the people on it still work at the Whitehouse. So there was no delay by disbanding it. The testing kits from overseas had a 48% false negative rate which is why they were rejected.

        • Submitted by Pat Terry on 03/16/2020 - 05:12 pm.

          That is an outright falsehood. Bolton disbanded the pandemic team. We are dangerously unprepared for this in large part due to Trump’s incompetence. The fact you are repeating false information about the dangers and making flu comparisons demonstrates the problem of having an incompetent president.

          • Submitted by Bob Barnes on 03/16/2020 - 08:19 pm.

            Wrong. The people on that pandemic team are STILL in the White House. Here is Dr Fauci himself: “Earlier this week, Democrats asked Dr. Anthony Fauci, a member of the president’s coronavirus team who leads the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, about the decision to cut the White House’s National Security Council Directorate for Global Health Security and Biodefense. He was asked whether it had been a “mistake.”

            Fauci said no, but added that it would also have been “nice” to have it around.

            “I wouldn’t necessarily characterize it as a mistake. I would say we worked very well with that office. It would be nice if the office was still there,” he said.”

            The Flu IS actually worse than covid19 at least so far. It’s very unlikely that covid19 will cause as many deaths as the Flu does every year. Covid19 has been around since sometime in November (given the earliest reports of it and the incubation times etc).. and so far less than 7,000 have died .. in that same time frame roughly (oct thru Feb), the flu has killed 12,000 in the US alone. From the data that is currently available, covid19 is no worse than the Flu in terms of mortality rate. Granted we don’t have a lot of good data on Covid19 yet but as more comes in, the mortality rates are coming down.

            • Submitted by Paul Udstrand on 03/17/2020 - 08:55 am.

              Bob, Fauci was NOT on the team that was disbanded, THAT team was specifically tasked to recognize, and organize responses to pandemics. Fauci is and was the director of NIAID. He was tapped for the COVID response AFTER it emerged. Yes, buys like Fauci would’ve been involved in a pandemic response, just like all of the other public health professionals in the country, but he was NOT on the team that Trump or Bolton fired and disbanded. You’re claim that this team “remained” in the White House somehow after being eliminated is simply false. When this pandemic started Fauci was doing his job over at NIAID, he was NOT working the White House.

            • Submitted by Tom Crain on 03/21/2020 - 10:50 am.

              Fauci contradicts himself. By thinking it would be ‘nice’ if the office was still there he implies that would be better having it intact than disbanding it. This implies that it was, in fact, a ‘mistake’ to remove it.

              I’ve watched Fauci answer these political questions and he’s pretty good at deflecting. It will be interesting to hear his unvarnished opinion when this is over and he does not work for this administration.

        • Submitted by Pat Berg since 2011 on 03/16/2020 - 06:01 pm.

          Do you have a cite for that?

          • Submitted by Bob Barnes on 03/16/2020 - 08:28 pm.

            Dr. Nicole Saphier …

            Also, the Obama Administration regulated private labs so they had to apply with the FDA before they could even make a test for something like Covid19. Trump’s Admin got rid of that regulation (which is why the Mayo is also now making their own tests). If you want to blame anyone for the testing kit failures, blame the people at the CDC.. they were the ones that screwed up their first tests.

            • Submitted by Paul Udstrand on 03/17/2020 - 09:13 am.

              The blame here clearly falls on the White House. You can’t keep pointing a different president who’s not in any way involved in the current crises, or responsible for the federal response. Trump has been in charge of the federal government for over three years now, and it’s NOT the same government that Obama ran… Trump and his followers have been bragging about their new and improved swamp for years now, the idea that Obama is somehow responsible for the government that Trump runs is simply facile.

              The testing fiasco can be directly traced back to the incompetent leadership residing the White House. At a time when we needed an organized and well prepared response directed by a team of professionals dedicated to pandemic responses… we didn’t have one because Trump fired them and eliminated their office in 2018.

              In a national an international crises like this you need leadership in the White House, on an executive level. The people who would have coordinated our response and testing with international partners, and ironed out bureaucratic kinks regarding COVID testing simply weren’t there. The reason we had these delays and chaotic response was that agencies weren’t getting any clear coherent direction.

              In theory a competent president could assemble a group, although there would still a delayed response compared to having a group in place (like Obama did). But we’re stuck with Donald Trump. Trump’s private sector leadership model of avoiding responsibility and leaving departments to fend for themselves effectively sabotaged the government’s response. At a time when we needed a White House pushing a COVID testing respons, we had a president who was a afraid of testing that would reveal a much higher level of infection than he was describing publicly. Pence was out there bragging about Trumps leadership keeping infection down… well if we’d had the testing we should have had, THAT lie would have been revealed weeks ago. You simply cannot over estimate the effect of competent leadership in a crises like this.

            • Submitted by Tom Crain on 03/21/2020 - 11:08 am.

              Dr. Nicole Saphier is a telegenic cable news (Fox, MSNBC) guest medical expert. She is a graduate from Ross University of Barbados specializing in breast cancer. She is the author of “Make America Healthy Again”.

              Bob’s source appears to be this Breitbart story


              Snopes gives her claim “The United States “refused” COVID-19 diagnostic tests offered by the World Health Organization.” a MIXED rating.

              What’s True
              The U.S. did not use COVID-19 diagnostic tests produced by the World Health Organization (WHO) in favor of producing its own.

              What’s False
              The U.S. did not turn down an offer to use those tests (as no such offer was extended), nor was it unusual for the United States to design and produce its own diagnostic tests in lieu of those made elsewhere.

        • Submitted by Moira Heffron on 03/19/2020 - 09:47 am.

          I feel strongly that we all should cite sources when we make what seem to be factual assertions like this failure rate. It may be so, I don’t know without some support. Let’s not turn MinnPost into Facebook.

      • Submitted by Miriam Segall on 03/17/2020 - 07:09 pm.

        Yes, I have also seen reports that the Trump administration refused to use a “foreign” test and wanted our private sector to come up with an “American” one. Par for the course. We already know that Trump is not responsible for anything that happens in this pandemic, and the additional serious illnesses and deaths that will result from our inability to test earlier and more widely are not on his head.

  4. Submitted by Gretchen Roberts on 03/16/2020 - 01:24 pm.

    Las Vegas Casinos are shutting down. What about the Tribal Casinos in
    Minnesota? Huge gatherings of people and hands, literally, on everything.

    • Submitted by Pat Terry on 03/16/2020 - 05:13 pm.

      They absolutely should be shutting down. Unfortunately, because their are sovereign entities, neither the state nor federal government can make them. Hopefully they will figure it out soon.

      • Submitted by Paul Udstrand on 03/17/2020 - 09:19 am.

        Oh, so now we’re all epidemiologists who can tell tribal governments what they should do? And tribal sovereignty is a public threat?

        Pandemics are no excuse for colonial mindsets, let’s get our own governance in order before we complain about the tribal governments shall we?

        The tribal casinos are following CDC guidelines like everyone else:

  5. Submitted by Jon Ruff on 03/17/2020 - 11:30 am.

    I guess the message here is to respect the authors ( Thanks Greta ), and ignore the round-about of opinion that follows by “the usual suspects”.
    Regardless of fault people are getting the disease whether they show symptoms or not. Without the test there is no record for reference and mitigation.
    My “close personnal friend” , in a phone conference with one of her doctors ,was told that she probably had the virus over the last two weeks.So I may well have also. No test for her, no test for me as we don’t have elevated temperatures currently.

    • Submitted by Paul Udstrand on 03/18/2020 - 08:50 am.

      Actually Jon, with all due respect to the author, the primary factors limiting testing for the last week or so have been dwindling supplies of testing material like re-agent and swabs. This is why providers are limiting testing and prioritizing (and probably why you and your wife weren’t tested). MDH has been talking about these shortages for over a week now but for some reason I see no mention of it in this article. It doesn’t matter how many testing kits are available, or how many labs are certified to test, if they don’t have the supplies they need to collect the specimens and run the test kits. This is a nationwide problem, not just a MN problem. We’re not going to see much increase in testing despite the additional labs and test kits until these the supply is replenished and stabilized at the necessary rate.

      Now these shortages are unnecessary, and not playing critical factors elsewhere in the world because most of those countries didn’t disband the offices and teams that anticipate such scenarios, ramp up production, stockpile, and iron out supply chain problems.

      Here’s an article on the supply problem in the Strib today:

  6. Submitted by cory johnson on 03/18/2020 - 07:33 am.

    The real story of Trump dissolving the response team:

    • Submitted by Paul Udstrand on 03/18/2020 - 09:04 am.

      I’m afraid this opinion piece is severely flawed. Obviously the re-org produced a bio-defense regime that has a failed on multiple accounts, so whatever criticisms the author may have about the old regime are moot.

      Calling it a “re-org” instead of a dissolution is sophomoric. The fact is that critical personal were fired, and the office they worked in no longer exists.

      It may well be the case that the regime Trump inherited was flawed, but his job is fix flawed things, not make them worse. He made it worse. You can try to argue that he made it worse by re-organizing it rather than disbanding an office, but it’s a distinction in search of a difference.

      • Submitted by Paul Udstrand on 03/18/2020 - 09:23 am.

        By the way, although Bolton got some good press for his criticisms of Trump a while back, the guy has always been duffus. Any idiot would have recognized Trump’s incompetence and the Giuliani fiasco in the Ukraine so celebrating Bolton’s ability to spot the bloody obvious was always an exercise in obeisance. No mater who ran the re-org, they got it wrong and damaged the countries ability to respond to epidemics and pandemics.

    • Submitted by Rachel Kahler on 03/19/2020 - 10:14 am.

      Lol. When companies “reorganize,” they get rid of people. So…there’s a reason the article is under opinion.

  7. Submitted by Paul Udstrand on 03/19/2020 - 04:22 pm.

    And almost on cue… Here’s Trump in a nutshell: Testing isn’t his problem-

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