This post was originally written April 7, 2020. It was last updated May 18, 2020.
Access to COVID-19 testing remains one of the most critical pieces to addressing the pandemic. Yet in the US, swab tests remain in short supply, creating a set of unique challenges. Many sick people are not able to get a concrete diagnosis that would inform their treatment, people without symptoms have no idea if they’ve been exposed to the virus or not, and we still know very little about the virus overall. As a result, most of us remain on a stay at home order, without a clear end date because we don’t have enough testing capacity to track the virus accurately and get the spread under control.
With the recent FDA approval of the first COVID-19 antibody test in the US, Parsley Health will begin offering antibody tests for members in states where it’s available starting Tuesday April 7, 2020. Our hope is that this can give members the information they need to make important decisions about their health.
We’ve seen that in countries where testing is widely available, such as in South Korea, where over 466K people have been tested , primarily using nasal or oral swabs , the government has been better able to track the virus, isolate the sick, and slow the spread. This has protected their healthcare system from being overrun and has contributed to South Korea’s lower overall fatality rate.
Here’s what you should know about the testing options available to you now.
This has been the most common type of test available to determine if someone has an active case of COVID-19. It uses polymerase chain reaction (PCR) testing. A medical professional uses a swab, similar to a Q-tip, to collect mucus from your nasopharyngeal or oropharyngeal passages—the inner compartments located deep inside your nasal and oral cavities. PCR testing works by directly detecting the presence of the virus, rather than the presence of the body’s immune response or antibodies. Preliminary data suggest that this testing may have a high false-negative reporting rate—meaning people that actually have the virus may wrongly receive a negative test result.
This is the newest category of testing that is designed for rapid detection of SARS-CoV-2 by analyzing fragments of proteins found on or within the virus by collecting a sample from a person’s nasal cavity—similar to PCR testing. One of the main advantages of an antigen test is that it just takes a matter of minutes to receive results. However, antigen tests are very specific for the virus, but are not as sensitive as PCR tests. This means there is a higher chance of false negatives, so negative results do not necessarily rule out infection. Because of this, negative results from an antigen test may need to be confirmed with a PCR test prior to making definitive decisions regarding diagnosis or treatment.
This type of test looks for antibodies, which are specific blood proteins created by your immune system when it comes into contact with a foreign invader. Unlike the above two tests, an antibody test is performed by analyzing a patient’s blood sample. Antibody testing is the only way to detect if you have previously been exposed to the virus, even if you are no longer actively infected.
Antibody tests in general are not new, in fact they are routinely used for confirming the diagnosis of Lyme disease, HIV, chickenpox, and even food sensitivities . For COVID-19 antibody testing, there are commonly two different subclasses of antibodies that can be used—immunoglobulin (IgG) and immunoglobulin M (IgM).
IgM antibodies are the first to be made by the body to defend against a new infection. After the first 5-7 days following exposure , IgM antibodies start to disappear and the IgG antibody type replaces IgM as the predominant antibody to the virus.
COVID-19 antibody tests work by detecting whether the specific types of antibodies in your blood match those that correlate with the SARS-CoV-2 antigen, the virus responsible for COVID-19. If both IgM and IgG antibodies are still present in your system, we will know that you have recently been exposed. If you only have IgG antibodies, it means it’s likely been over two weeks since you were infected and if you’ve been asymptomatic for over 72 hours, then you have an inactive infection that’s no longer contagious. At this time, it remains unknown how long IgG antibodies will remain in the body and if they will protect you against getting infected again (like they do with ensuring you don’t get a repeat case of the chickenpox).
Knowing your status will tell you if you have been exposed to the virus as well as whether your body has cleared the virus. Testing is critical to understanding your own health and helping to slow the spread of COVID-19 infection.
The more we get community testing out into the world, the faster we can help slow the spread of the disease. Knowing who and who has not mounted an antibody response is critical to our understanding of disease progression.
At Parsley Health, we are currently able to offer antibody testing to our members across the country. Although the type of test may vary by availability in your region, all will test for IgG antibodies while some may test for both IgG and IgM antibodies. It’s important to note that the FDA does not recommend using antibody tests to diagnose active infection without confirmation from another form of testing, such as PCR or antigen testing.
If you’re a Parsley Health member and your antibody test is positive for any of the markers, your Parsley Health doctor will advise you on next steps. Depending on which antibodies you show we will recommend a different length of time to further quarantine. For instance, if you have IgM antibodies we may recommend retesting after 2-3 weeks to ensure they have cleared.
Unlike the deep nasal and oral swab tests which can only detect if you currently have the virus, antibody testing will also help determine if you’ve already had it. All antibody tests recommended to our members have undergone clinical validation studies and are thoroughly vetted by our doctors.
Because there are several unreliable antibody tests being marketed, our team is committed to ensuring we are offering the most accurate testing available. Parsley recommended antibody tests agree with the results from PCR swab testing 98-100% of the time and the test’s ability to correctly identify those without the disease is estimated to be about 98-100%.
With that in mind, no diagnostic test is 100% accurate and as our understanding of COVID-19 continues to evolve we will remain apprised of the latest developments in testing to ensure we are offering our members the most up-to-date and comprehensive testing available.
The duration of immunity for COVID-19 post-infection is not yet fully understood. Additionally, the presence of positive antibodies does not mean you are immune to the virus and we do not know if people who have antibodies can still spread the virus. Therefore, positive antibodies cannot determine if re-infection will occur.
At Parsley Health, we are currently able to order antibody testing for our members when appropriate. If you’re a Parsley Health member interested in antibody testing, please contact your care team in My Parsley Health to receive more information about options available in your area.
Dr. Kerri Masutto is an Internal Medicine primary care physician with an integrative, whole-person approach to medicine who graduated from The College of Medicine at University of Illinois. With training in primary care, plus ongoing education through the Institute for Functional Medicine she creates a unique healing experience for anyone looking to improve their health and their life.