When Should You Get a COVID-19 Test? What About an Antibody Test?
By Kristen Fischer
As more testing for COVID-19 rolls out, you may be wondering whether you should get tested.
Tests for COVID-19 include the polymerase chain reaction (PCR) diagnostic test, which is a nasal swab. There's also the antibody test, a blood test that can tell whether you had an infection in the past.
So, should you wait till you have symptoms to go ahead and get tested? Or is it worth it to see whether you had an infection in the past?
Getting Tested for COVID-19
People exposed to the virus who have had close contact with a confirmed case should get tested whether or not they have symptoms, Amira Roess, PhD, a professor of global health and epidemiology at George Mason University, told Healthline.
"By identifying individuals who are positive early in disease progression before they develop symptoms and implementing public health interventions, we can prevent a large percentage of infections. This is key, because we have learned that asymptomatic infection is a key driver of this epidemic," she said. "Finding asymptomatic individuals will allow us to prevent them from spreading the virus."
On the flip side, people with no exposure history and no symptoms should not get tested, Roess adds.
The virus's incubation period is around 5 to 7 days, but it can be up to 14 days.
If you get tested too early after exposure, it can be possible that you have a false-negative test, notes Dr. Abraar Karan, an internal medicine doctor at the Brigham and Women's Hospital and Harvard Medical School.
A positive polymerase chain reaction (PCR) means that you have detectable viral RNA. "This does not necessarily say if you are infectious," Karan said.
Despite a positive PCR, studies have shown for some people there was little to no culturable virus after about 9 to 10 days. This means a person had an infection with the virus but tested positive long after they were no longer infectious to others.
However, PCR can remain positive for several weeks after active infection. "This means you are detecting viral RNA but not that you are infectious to others," Karan said.
The Centers for Disease Control and Prevention (CDC) says a positive test means you should isolate at home for 10 days.
Dr. Sophia Yohe, director of the University of Minnesota Molecular Diagnostics Laboratory and medical director for the Fairview/M Health COVID-19 testing lab, points out that the test only helps if you're going to be active in protecting yourself and others.
If you don't plan to isolate yourself if you're positive, the test is moot, says Yohe.
Antibody tests looking for immunoglobulin M (IgM) and immunoglobulin G (IgG) levels can tell whether you recently had an infection or had one in the past.
"Antibody testing should be done in individuals who have COVID-19 symptoms but did not have immediate access to a COVID-19 PCR test," said Dr. Amy B. Karger, medical director of the University of Minnesota Health West Bank Laboratory.
Typically, it takes about a week or two to develop antibodies after symptoms start. That's why the antibody test isn't ideal for diagnostic purposes if you've had symptoms for less than a week, she says.
Antibody testing isn't recommended for those within 8 days of symptom onset, Karger says.
"In these individuals, only the COVID-19 test (PCR test) should be used for acute diagnosis," she told Healthline.
People within that time frame may not have developed antibodies yet, and therefore there's a high risk for a false-negative result.
Additionally, there are issues with how accurate these tests are.
In early February, the Food and Drug Administration (FDA) authorized the emergency use of tests that can detect the new coronavirus.
This means the tests can be released before they're evaluated by the FDA for efficiency.
When to Get Both Tests
Federal guidelines recommend testing people with both tests if they present 9 to 14 days after symptoms start.
Antibody testing is useful for people with asymptomatic infections who experienced a COVID-19-like illness 14 days prior.
It's also useful if you were exposed to a person with COVID-19 14 days prior. In those cases, it can determine whether you had the virus in the past.
Experts haven't yet said that having the antibodies means you've got protective immunity, but evidence does support that, Karger says.
Additionally, it's possible to get a false positive for antibodies from the test, especially if you had no symptoms of COVID-19.
"Until we have additional data on these key factors, experts do not recommend assuming immunity with a positive antibody test," Karger said.
Physical distancing and mask use should still continue if you have a positive antibody test.
If you do test positive for antibodies, there's not much to do. The test simply provides information about exposure history to the new coronavirus and doesn't require any specific action, Karger says.
If you already got a PCR test and then go on to be exposed or develop symptoms, you should be retested.
The CDC advises healthcare workers who had a positive PCR test can return to work safely if two consecutive specimens collected within 24 hours apart come back negative.
Unfortunately, data is lacking on whether asymptomatic, non-exposed individuals who previously had a negative PCR test should get periodic testing, Yohe says.
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EcoWatch Daily Newsletter
By Teri Schultz
Europe is in a panic over the second wave of COVID-19, with infection rates sky-rocketing and GDP plummeting. Belgium has just announced it will no longer test asymptomatic people, even if they've been in contact with someone who has the disease, because the backlog in processing is overwhelming. Other European countries are also struggling to keep up testing and tracing.
Meanwhile in a small cabin in Helsinki airport, for his preferred payment of a morsel of cat food, rescue dog Kossi needs just a few seconds to tell whether someone has coronavirus.
<div id="bfda0" class="rm-shortcode" data-rm-shortcode-id="c60b1a0dedbedbe5e0ce44284aff852f"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1308390775328251906" data-partner="rebelmouse"><div style="margin:1em 0">Covid-19 dogs started their work today at the Helsinki Airport at arrival hall 2B. Dogs have been trained to detect… https://t.co/nw4mrw6eJM</div> — Helsinki Airport (@Helsinki Airport)<a href="https://twitter.com/HelsinkiAirport/statuses/1308390775328251906">1600779644.0</a></blockquote></div><p>If it were left to Kossi and his pals, crowds of potential virus carriers could be cleared in a fraction of the time for a fraction of the cost with none of the physical discomfort that accompanies the current nasal swab test based on the polymerase chain reaction (PCR) method.</p>
No Human Nose Needed<p>A dog can sniff a cloth wiped on a wrist or neck and immediately identify if it comes from someone who has contracted the virus as much as five days before any symptoms appear which would lead a person to go into isolation. "A dog could easily save so so, so many lives," University of Helsinki veterinary researcher Anna Hielm-Bjorkman told DW, who says their testing has shown an accuracy level of nearly 100%.</p><p>It was originally her idea to see whether Kossi, a talented disease-detection dog, could redirect his skills in sniffing out mold, bedbugs and cancer to detecting the new virus just as it started to spread in Europe. "It took him seven minutes to figure out 'okay, this is what you want me to look out for," Hielm-Bjorkman said. "So that totally blew our minds."</p><p>Susanna Paavilainen, the executive director of the Wise Nose scent-detection foundation and the woman who saved Kossi from euthanasia in a Spanish shelter eight years ago, immediately started retraining her dogs to find the coronavirus.</p><p>Miina, who used to track a young girl's blood sugar levels by scent, quickly came on board, along with two others already working in disease detection. In all, they hope to train 15 dogs in the first phase.</p><p>Hielm-Bjorkman said once they discovered the new capabilities, while the normal academic procedure would be to test, publish and get peer-reviewed, their first instinct was to get the dogs into service. "[Researchers] who are actually publishing," she noted wryly, "are not at the airports."</p>
Wags, Not Wages<p>But for that, they needed permission and ideally, some funding. Vantaa Deputy Mayor Timo Aronkyto, who is also responsible for airport security, saw the benefit straight away. "It took me two minutes," he told DW.</p><p>However, his funding options were limited to about $390,000 total for the four-month pilot project aiming to prove that results from the dog tests are at least as accurate as the PCR test. Anyone who tests positive at the voluntary canine site is requested to go to the medical unit for confirmation.</p><p>The interest of Aronkyto, a trained physician, is rooted in both health and wealth. "Our testing at the airport costs more than 1 million [euros] (USD $1.2 million) a month at the moment," he said, explaining he expects that to go up to €3 million (USD. $3.5 million) per month in winter. "These dogs would be much cheaper," he pointed out.</p><p>He's optimistic support will grow as data from the current pilot project accumulates, explaining there is already work underway to change Finnish legislation so eventually sniffer dogs would have the same "authority" as customs dogs.</p><p>Aronkyto anticipates one animal performing both functions in the near future. He plans to continue this level of funding from his city budget into next year but that doesn't train new dogs nor expand the capacity beyond the four that split shifts currently at the airport, even as infection rates rise.</p>
Helsinki Hesitates<p>Notably, however, the Finnish government has not signaled it would like to pick up the program itself, despite a huge surge in publicity and, as Hielm-Bjorkman and Paavilainen emphasize, interest from other countries. Travelers have been eager to participate, waiting in line more than an hour at times.</p><p>Finnish ambassador in Ramallah, Palestine, Paivi Peltokoski, praised the experience after a recent trip but, apparently, her enthusiasm is not overly contagious.</p>
<div id="d9823" class="rm-shortcode" data-rm-shortcode-id="61d382f115fe66a44eb793d9ebee3d94"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1318564228450615299" data-partner="rebelmouse"><div style="margin:1em 0">I was tested negative by two #coronadogs upon arrival at the #Helsinki airport in #Finland. Later a medical test ve… https://t.co/cGlWQn8DJb</div> — Päivi Peltokoski (@Päivi Peltokoski)<a href="https://twitter.com/PaiviPeltokoski/statuses/1318564228450615299">1603205184.0</a></blockquote></div><p>"If the government would see this already as something that they would believe in," Hielm-Bjorkman said, she could envision training hundreds of dogs, stationing sniffers at concert halls or sports matches or elderly care homes. She adds there's a need for a "paradigm shift" for both medical professionals and the public.</p><p>Usually it's doctors telling patients if they're sick, she explained, and "here it's a dog handler."</p>
Little Political Will on German Project<p>This situation is not limited to Finland. In Germany researchers also <a href="https://www.dw.com/en/german-sniffer-dogs-show-promise-at-detecting-coronavirus/a-54300863" target="_blank" rel="noopener noreferrer">announced promising results</a> with canines <a href="https://www.dw.com/en/coronavirus-german-military-training-sniffer-dogs/a-54062180" target="_blank" rel="noopener noreferrer">detecting COVID-19</a>, but no dogs have been used anywhere so far. And then, says Professor Holger Volk of the University of Veterinary Medicine Hanover, there has been insufficient political will or funding to move the project forward, something he called "very troubling" especially with a resurgent infection rate.</p><p>"When we started this whole project, we we did it because we wanted to help to stop the pandemic," Volk told DW. "It's really has been a very frustrating ride. I have had a lot of naysayers in the whole process. If I wasn't a very determined person, having done a lot of research, I would have probably stopped it."</p><p>He agrees with Hielm-Bjorkman's assessment that "it's just not in the perception of doctors that dogs are able to do this precise work." But he also echoes her faith in the vast potential of their discovery. "If you had a dog who could sniff every day quickly your cohort of workers, for example," he said, "think about the impact. You could continue having a workplace."</p><p>Speaking of workplaces, Susanna Paavilainen is starting to think if Finland doesn't want to unleash the dogs' potential at home, she and Kossi might accept one of the many requests from all over the world to provide training. "We can move because Kossi likes warm weather," she says, petting her star sniffer.</p>
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