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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By D. André Green II
One of nature's epic events is underway: Monarch butterflies' fall migration. Departing from all across the United States and Canada, the butterflies travel up to 2,500 miles to cluster at the same locations in Mexico or along the Pacific Coast where their great-grandparents spent the previous winter.
Millions of People Care About Monarchs<p>I will never forget the sights and sounds the first time I visited monarchs' overwintering sites in Mexico. Our guide pointed in the distance to what looked like hanging branches covered with dead leaves. But then I saw the leaves flash orange every so often, revealing what were actually thousands of tightly packed butterflies. The monarchs made their most striking sounds in the Sun, when they burst from the trees in massive fluttering plumes or landed on the ground in the tussle of mating.</p><p>Decades of educational outreach by teachers, researchers and hobbyists has cultivated a generation of monarch admirers who want to help preserve this phenomenon. This global network has helped restore not only monarchs' summer breeding habitat by planting milkweed, but also general pollinator habitat by planting nectaring flowers across North America.</p><p>Scientists have calculated that restoring the monarch population to a stable level of about 120 million butterflies will require <a href="https://doi.org/10.1111/icad.12198" target="_blank">planting 1.6 billion new milkweed stems</a>. And they need them fast. This is too large a target to achieve through grassroots efforts alone. A <a href="https://www.fws.gov/savethemonarch/CCAA.html" target="_blank" rel="noopener noreferrer">new plan</a>, announced in the spring of 2020, is designed to help fill the gap.</p>
Pros and Cons of Regulation<p>The top-down strategy for saving monarchs gained energy in 2014, when the U.S. Fish and Wildlife Service <a href="https://www.fws.gov/southeast/pdf/petition/monarch.pdf" target="_blank">proposed</a> listing them as threatened under the Endangered Species Act. A decision is expected in December 2020.</p><p>Listing a species as endangered or threatened <a href="https://www.fws.gov/endangered/esa-library/pdf/listing.pdf" target="_blank">triggers restrictions</a> on "taking" (hunting, collecting or killing), transporting or selling it, and on activities that negatively affect its habitat. Listing monarchs would impose restrictions on landowners in areas where monarchs are found, over vast swaths of land in the U.S.</p><p>In my opinion, this is not a reason to avoid a listing. However, a "threatened" listing might inadvertently threaten one of the best conservation tools that we have: public education.</p><p>It would severely restrict common practices, such as rearing monarchs in classrooms and back yards, as well as scientific research. Anyone who wants to take monarchs and milkweed for these purposes would have to apply for special permits. But these efforts have had a multigenerational educational impact, and they should be protected. Few public campaigns have been more successful at raising awareness of conservation issues.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="91165203d4ec0efc30e4632a00fdf57d"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/KilPRvjbMrA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
The Rescue Attempt<p>To preempt the need for this kind of regulation, the U.S. Fish and Wildlife Service approved a <a href="https://www.fws.gov/savethemonarch/pdfs/Monarch%20CCAA-CCA%20Public%20Comment%20Documents/Monarch-Nationwide_CCAA-CCA_Draft.pdf" target="_blank">Nationwide Candidate Conservation Agreement for Monarch Butterflies</a>. Under this plan, "rights-of-way" landowners – energy and transportation companies and private owners – commit to restoring and creating millions of acres of pollinator habitat that have been decimated by land development and herbicide use in the past half-century.</p><p>The agreement was spearheaded by the <a href="http://rightofway.erc.uic.edu/" target="_blank">Rights-of-Way Habitat Working Group</a>, a collaboration between the University of Illinois Chicago's <a href="https://erc.uic.edu/" target="_blank" rel="noopener noreferrer">Energy Resources Center</a>, the Fish and Wildlife Service and over 40 organizations from the energy and transportation sectors. These sectors control "rights-of-way" corridors such as lands near power lines, oil pipelines, railroad tracks and interstates, all valuable to monarch habitat restoration.</p><p>Under the plan, partners voluntarily agree to commit a percentage of their land to host protected monarch habitat. In exchange, general operations on their land that might directly harm monarchs or destroy milkweed will not be subject to the enhanced regulation of the Endangered Species Act – protection that would last for 25 years if monarchs are listed as threatened. The agreement is expected to create up to 2.3 million acres of new protected habitat, which ideally would avoid the need for a "threatened" listing.</p>
A Model for Collaboration<p>This agreement could be one of the few specific interventions that is big enough to allow researchers to quantify its impact on the size of the monarch population. Even if the agreement produces only 20% of its 2.3 million acre goal, this would still yield nearly half a million acres of new protected habitat. This would provide a powerful test of the role of declining breeding and nectaring habitat compared to other challenges to monarchs, such as climate change or pollution.</p><p>Scientists hope that data from this agreement will be made publicly available, like projects in the <a href="https://www.fws.gov/savethemonarch/MCD.html" target="_blank">Monarch Conservation Database</a>, which has tracked smaller on-the-ground conservation efforts since 2014. With this information we can continue to develop powerful new models with better accuracy for determining how different habitat factors, such as the number of milkweed stems or nectaring flowers on a landscape scale, affect the monarch population.</p><p>North America's monarch butterfly migration is one of the most awe-inspiring feats in the natural world. If this rescue plan succeeds, it could become a model for bridging different interests to achieve a common conservation goal.</p>
The annual Ig Nobel prizes were awarded Thursday by the science humor magazine Annals of Improbable Research for scientific experiments that seem somewhat absurd, but are also thought-provoking. This was the 30th year the awards have been presented, but the first time they were not presented at Harvard University. Instead, they were delivered in a 75-minute pre-recorded ceremony.