Key takeaways:
- We now have two main types of tests for coronavirus (COVID-19): molecular and serological.
- The fastest test to be authorized by the FDA, created by Abbott, can return results in as little as 5 minutes.
- The FDA has just issued the first authorization of an at-home collection molecular test kit by LabCorp.
- Estimates of testing in the U.S. suggest that only 320 out of every 100,000 people have been tested for COVID-19.
As COVID-19 has reached pandemic status and the number of cases continues to grow, widespread availability of diagnostic testing is critical in helping identify and control the emergence of this rapidly spreading and serious illness.
In early January, China released the genetic sequence of the coronavirus, which allowed the CDC to create the first test for COVID-19 in the United States. In late February, private manufacturers began developing their own tests once they received virus samples from the CDC. In an effort to balance the urgent need for test availability with testing accuracy, the FDA has issued guidance that enables test developers to begin testing patients prior to the FDA’s review of their validation data.
We now have two main types of tests: molecular and serological. The FDA has officially authorized over 20 manufacturers to make molecular tests, and over 40 manufacturers have provided notification that they have validated and are offering serological tests.
The amount of information coming out about new test development — from at-home testing to portable/point-of-care tests with faster results — can be overwhelming, and it may be difficult to keep track of when and where these tests will be available. We’ll keep this page updated with the latest news.
What is the molecular test, and how does it work?
Molecular tests were the first type of test for COVID-19, used by both the World Health Organization (WHO) and the Center for Disease Control and Prevention (CDC). Currently, 22 companies have been issued authorization by the FDA to distribute these tests, and over 50 additional companies have notified FDA they have begun testing patients with their internally validated tests and will be submitting authorization requests.
What’s the science behind it?
In a patient with a COVID-19 infection, genetic material from SARS-CoV-2, the virus that causes COVID-19, is generally detectable in upper and lower respiratory specimens. We now have several ways to collect these samples, including using at-home test kits. More on this below.
In acute respiratory infections, molecular tests are routinely used to detect the presence of viral genetic material in a sample. The specific technique that’s used is called reverse transcription polymerase chain reaction, or RT-PCR, where genetic material from a sample is copied and then compared to the genetic sequence of the virus you’re trying to detect.
Provider-administered swab tests for coronavirus
Molecular tests typically involve inserting a 6-inch long swab into the back of the nasal passage through one nostril and rotating the swab several times for 15 seconds. This process is then repeated through the other nostril. The swab is then inserted into a container and sent to a lab for testing.
Abbott Laboratories recently announced a point-of-care swab test that can deliver results in as little as 5 minutes. With the introduction of portable/point-of-care testing, sample collection can even be done entirely in the provider offices or even the parking lot of a drive-thru testing site.
Provider-administered saliva tests for coronavirus
Recently, the FDA authorized the first molecular test that uses saliva (instead of deep nose or throat swabs), developed by Rutgers’ RUCDR Infinite Biologics. These tests are as accurate as the swab-based tests, and they may help with the current shortage of testing swabs since patients just need to spit into a collection device.
At-home tests for coronavirus
The FDA authorized the first at-home collection molecular test, called Pixel by LabCorp, on April 20. The test kits contain supplies to collect samples, including a nasal swab which you send back to the lab for testing. Unlike other swab-based tests, Pixel uses swabs that only need to go as far as the nostril, instead of deeper into the nasal passage. A study led by the UnitedHealth Group suggests that results from self-collected testing are similar in accuracy to provider-collected testing.
Previously, the FDA had not authorized any at-home tests, but several companies, including Everlywell and Nurx, had begun to sell them anyway. However, many of these companies stopped selling these tests after the FDA issued a statement warning consumers that the tests were unauthorized.
The authorization of LabCorp’s at-home collection test is a big step forward as FDA works with test developers in this space. At-home collection tests can help expand testing, reduce the demand for personal protective equipment (PPE), and minimize frontline healthcare worker exposure. The Pixel kits will initially be available to healthcare workers and first responders who may have been exposed to the virus or are symptomatic. In the coming weeks, LabCorp intends to make the test available to consumers. Currently, the FDA has not authorized any tests to be entirely used and processed at home.
How long does it take to get results with molecular tests?
Most RT-PCR tests can take anywhere from a few hours to a few days, but new rapid diagnostic tests for COVID-19 show promise of results in less than an hour. Examples of rapid diagnostic tests that have been recently authorized include those by:
- Abbott: results in as little as 5 minutes
- Mesa Biotech: results in as little as 30 minutes
- Cepheid: results in as little as 45 minutes
The new saliva-based test through Rutgers can deliver results in 24 to 48 hours, and the first at-home collection test through LabCorp takes about 1 to 2 days.
How accurate are molecular coronavirus tests?
Since molecular tests detect the presence of viral genetic material, a positive result indicates an active COVID-19 infection but does not rule out bacterial infections or co-infections with other viruses.
With every test, there’s a limit at which you can still detect a signal. A negative result with the molecular test means that the virus that causes COVID-19 was not found in the sample above the limit of detection, but it is still possible to have very low levels of the virus in the body.
If the test results come back positive, it is very likely that you have a COVID-19 infection. However, there’s a small chance that it could be a false positive, meaning that the test is positive, but you actually don’t have a COVID-19 infection.
If the test results come back negative, it means that the virus that causes COVID-19 was not found in the sample above the limit of detection. A false negative is possible, and should be considered in combination with your symptoms, travel history, and other possible ways of having been exposed. Additionally, the FDA advises anyone who tests negative with the saliva-based test to confirm the results with a second testing method.
What is the serological test, and how does it work?
Serological tests are now being developed and can help give us a broader picture of COVID-19 infection spread. Unlike molecular tests, serological tests can identify those that were infected and have recovered.
Currently, there are efforts to import already developed serological tests from other countries, as well as develop new tests in the U.S. Until recently, the FDA wasn’t authorizing serological tests like they did molecular tests. Companies simply had to notify the FDA that they had validated and were offering these tests, and include a disclaimer on their test results. Over 40 manufacturers have done this. The FDA issued their first approval for a serological test on April 1.
How is the serological test administered?
Serological tests rely on detecting antibodies in a blood sample, usually obtained through a simple finger prick. These tests do not require special equipment to process the results, which allows them to be used in laboratories or at point-of-care.
What’s the science behind it?
When you’re exposed to the virus, your body develops antibodies, which can take several days to over a week. Antibodies are proteins your body makes when mounting a response against invading germs.
The presence of immunoglobulin M (IgM) antibodies indicate recent exposure to COVID-19, while the presence of immunoglobulin G (IgG) antibodies indicate later-stage infection. The rapid response serological tests typically use a technique called enzyme-linked immunological assay (ELISA), which detects the presence of these antibodies to the virus.
How long does it take to get results with serological tests?
Serological tests are typically much faster than standard molecular tests. The FDA has authorized several serological tests, including one by Cellex that delivers results in about 15 minutes. Previously, Bodysphere announced the approval of a 2 minute serological test, but they later clarified as the test was not actually approved.
How accurate are serological tests?
Since it can take several days for the body to develop an antibody response to the virus, serological tests may not be useful in identifying a current infection alone. They have the potential of producing a false negative, a false result when you actually have the infection.
However, they can identify individuals who have had the infection and have recovered, suggesting that those people are now immune to the virus. It is still unclear how long any immunity lasts and if reinfection is possible.
As mentioned above, the FDA only just recently started authorizing serological tests, but many had been used for coronavirus testing prior to this under previous FDA guidelines. FDA authorization is still not required for these tests, but several companies have or plan to submit authorization requests, including Abbott, who recently announced the release of a serological test specific for IgG antibodies (later-stage infection) with plans to ship 1 million tests to customers immediately, and up to 20 million by the end of June.
How much does it cost to get tested?
The Families First Coronavirus Response Act mandates that COVID-19 testing is free whether or not you have insurance, meaning that you won’t have to pay anything out of pocket for medical services related to COVID-19 diagnostic testing.
Although COVID-19 testing is mandated to be free, you may be responsible for additional out-of-pocket costs if you are diagnosed with COVID-19 and require additional care. Recently, several insurers, including Aetna, Cigna, and Humana have announced that they will waive some of the out-of-pocket costs of COVID-19 treatment. Kaiser Permanente has also announced that they will waive all out-of-pocket costs for inpatient and outpatient services related to the treatment of COVID-19.
Who should be tested for COVID-19?
According to WHO, the most common symptoms of COVID-19 are fever, tiredness, and dry cough, with some patients experiencing aches and pains, nasal congestion, runny nose, sore throat, or diarrhea. These symptoms are typically mild with gradual onset but in some patients, this may escalate into more severe symptoms like high fever, shortness of breath, and severe cough.
Emergency warning signs that would require immediate medical attention include, but are not limited to:
- Trouble breathing
- Persistent pain or pressure in the chest
- New confusion or inability to arouse
- Bluish lips or face
Since test availability is still limited, not everyone can be tested and criteria may vary between states and local health departments. HeyDoctor by GoodRx currently offers a free COVID-19 assessment to help provide recommendations based on CDC guidelines on how and when self-quarantine at home, and when to seek testing or urgent medical attention.
The CDC has also issued guidance for how to prioritize testing, giving higher priority to:
- Hospitalized patients
- Healthcare workers
- Those with highest risk of severe illness if they got COVID-19
- First responders
- Individuals with symptoms
Ultimately, decisions about testing are at the discretion of state and local health departments and/or individual clinicians. If you have symptoms of COVID-19 but don’t need immediate medical attention, call your medical provider to determine if you need testing and/or where testing may be available.
How many people in the U.S. have been tested?
As of April 20, the COVID Tracking Project estimates that over 4 million people in the United States have now been tested. A combination of public and private labs are performing more than 100,000 tests per day.
Still, only about 320 out of every 100,000 people have been tested in the United States, compared to 800 in Italy and South Korea. However, testing rates vary significantly by state, with New York testing more than 1,200 per 100,000 people, and Texas testing only 174 per 100,000.
The American Enterprise Institute recently published a National Coronavirus Response plan that outlines how we can move from community-wide interventions that “slow the spread” (for example, social distancing) to case-based interventions (like testing and treatment) that allow states to start reopening. For this to happen, certain thresholds need to be met:
- Cases decreasing for at least 14 days straight
- Hospitals ready to safely treat all patients requiring hospitalization
- Having enough tests to test everyone with COVID-19 symptoms
- States having the ability to actively monitor all confirmed cases and contacts
Given this, it’s estimated that at least 750,000 tests per week nationwide would be sufficient as part of a strategy towards reopening, with supportive public-health infrastructure in place.
The bottom line
If you have an active COVID-19 infection, the molecular test will generally be more accurate unless you’ve started developing antibodies to the virus. The serological test will be able to tell you if you’ve had the infection and recovered (regardless of having symptoms or not). This can be useful in determining who may be able to go back to work or school. Rapid response, point-of-care tests and at-home tests are also being developed.
Although testing has increased, efforts are being made to try to keep up with demand, with testing availability and administration varying significantly across states. If you have symptoms consistent with COVID-19 and do not require immediate medical attention, contact your medical provider, or state or local health department to see if you should be tested.
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