10 Facts About COVID-19 Antibody Testing to keep you safe

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The Injection and Infusion Clinic follows protocols to support our patients in this time of the COVID-19 pandemic.

In line with safety and care standards, we’re coming up with blog posts like this one. It’s our way of informing people like you about the updates on COVID-19 and Covid-19 antibody testing.

COVID-19 is a new virus and studies have yet to reveal more about it. We’re here to share what we have researched so far about the virus. This blog refers to valid sources such as the CDC, FDA, and Mayo Clinic. 

One of the topics about COVID-19 is antibody testing. You might have heard that it’s not yet FDA-approved, since there has been no COVID-19 test approved by the FDA to this day. Although, recent studies reveal promising results of antibody tests. 

A longitudinal study conducted in the US showed that Diazyme IgM/IgG assays demonstrated low false-positive results among 235 patients who were thought to be COVID-19 free.

Another study published in September 2020 announces the development of an antibody test for the virus that causes COVID-19. The researchers from the University of Texas in collaboration with the Houston Methodist and other institutions developed the antibody test. It performed better than existing antibody tests in terms of sensitivity or accuracy. It also proved cost-efficient as it processed more plasma donor samples at a lower cost. 

Let’s uncover more facts about the antibody test to better understand its contribution to the detection of COVID-19.

1. What are the three different kinds of tests for COVID-19?

Molecular test: This includes diagnostic tests, nucleic acid amplification test (NAAT), RT-PCR, and LAMP test that can show the presence of COVID-19 in the body.

These tests are considered highly accurate and don’t require repetition for validation. RT-PCR test, which is commonly used, spots the genetic material in a sample. Healthcare practitioners perform the molecular test through nasal and throat swabs. Saliva can also be tested via spit in a tube. 

According to the CDC, the FDA approved diagnostic tests as rapid tests through the Emergency-Use Authorization (EUA). The importance of EUA will be discussed later in this blog.Antigen test: Antigen test spots the specific proteins of COVID-19. These are also rapid diagnostic tests that are accurate. But you need to be retested with a molecular test if your result turns out negative. Like the molecular test procedure, a healthcare practitioner performs the antigen test through nasal and throat swabs. Saliva can also be tested via spit in a tube.  Antigen test though is best done in the early phases of the infection as it can be less sensitive.

Antibody test: Known as the serology test, it shows past infection from COVID-19. It doesn’t detect the virus itself. At times, you’d need a second test for an accurate result. Your blood is drawn to see any presence of infection, which may stay in your body 1-12+ weeks after your recovery.

Serology assay may also be issued to the EUA after test performance and thorough review by the FDA.

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2. What is antibody testing for COVID-19?

An antibody test checks for antibodies immunoglobulins M and G or IgM and IgG found in the blood. IgM is the first antibody the body creates to fight an infection.

This happens at the onset of the infection. IgG protects and helps defend your body from infections. This shows up later in the course of infection. Antibody test measures the levels of both antigens as these indicate your body’s immune response to an infection.

Antibody tests can also help in identifying people who may have developed an immune response. These people may be qualified to donate plasma. Convalescent plasma may serve as an adjunct therapy for those who are severely sick from the infection.

Antibody tests can also serve as a support to NAAT, the gold standard of COVID-19 diagnosis. Dr. Liu and research associates concluded that the IgM-IgG antibody along with the RT-PCR test improved the accuracy of COVID-19 diagnosis. This is regardless of the severity of infection. The antibody test provided an effective complement to NAAT, which had false-positive results after the onset of COVID-19 infection.

Researchers in a more current study released in October 2020 also agreed that antibody testing complements NAAT. Dr. Caturegli and co-researchers said the findings of their study “provide valuable diagnostic support in patients who test negative by NAAT but remain clinically suspicious for COVID-19.”

3. What are the types of Covid-19 antibody testing?

Binding antibodies. It doesn’t show how effective your immune system is against the COVID-19. Rather, this detects whether or not you’ve developed antibodies against the virus. 

The two specific tests that detect binding antibodies are the point-of-care (POC) test and laboratory test with the use of enzyme-linked immunosorbent assay (ELISA) or chemiluminescent immunoassay (CIA).

Neutralizing antibodies. This is performed as a second step after you tested positive for binding antibodies. It shows if your antibodies are effective in stopping the virus from letting you get another COVID-19 infection. 

The two types of neutralization tests are the virus neutralization test (VNT) and pseudovirus neutralization test (pVNT).

4. What are the limitations of Covid-19 antibody testing?

There has been no test with a 100% accuracy rate. Some of these tests may have false-positive results since they can react with other coronaviruses. Examples are the common cold and seasonal flu. Antibodies may also be undetectable a few days upon catching the virus. Antibody tests can be used 15-35 days after the onset of symptoms.

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5. What is the Emergency-Use Authorization for antibody testing?

The FDA has yet to approve the COVID-19 antibody test, but they can release the EUA. The acting commissioner, Dr. Joshua Sharfstein of the FDA signed the first EUA in 2009. The following circumstances warrant its issuance:

  • Declared emergency: The FDA can release the EUA during a pandemic when there’s no time to gather all evidence about the efficacy of a test, drug, or device. 
  • Evidence suggestive of benefit to people: The FDA can release the EUA when evidence is supported by positive outcomes. 

Dr. Sharfstein is now the vice dean of the Public Health and Practice at the John Hopkins Bloomberg School of Public Health. He further mentioned one of the minimum requirements of the EUA, but not a sole standard for authorization.

It is the potential benefits outweigh the potential risks. It should be for a good reason that meets efficacy and safety minimum standards.

Thus, for the case of COVID-19 tests, the criteria include effectiveness in detecting antibodies and its potential benefits outweigh potential risks. So far, the FDA has issued more than 200 EUAs for tests at this time of the pandemic.

The FDA may review or cancel existing EUAs. It depends on the FDA’s evaluation of the product’s new information, efficacy, and safety performance. If it meets the criteria set by the FDA, only then can it be approved, cleared, and licensed.

6. Who should use covid-19 antibody testing?

It can be used on people 9-14 days after the onset of the infection. People are tested in the late phase where antibodies may have developed and are already detectable (Watson et al., 2020).

It can be offered as a support to polymerase chain reaction or antigen detection test. You can get tested if you once had symptoms of COVID-19 but you weren’t tested at that time. 

You can get tested before you undergo a medical procedure.

7. Do the presence of antibodies mean you’re immune to COVID-19?

Antibody testing shows the presence of antibodies but it doesn’t necessarily mean you are immune against COVID-19. The medical community has yet to investigate more about the body’s immunity to the virus. It’s safe to assume that even if you have positive antibodies, you may still catch the virus a second time.

8. What is the procedure for Covid-19 antibody testing?

Under a policy prescribed by the FDA, states or territories are responsible for authorizing laboratories to conduct testing. It’s best to contact your direct primary healthcare provider if they’re offering antibody tests.

The healthcare professional will get a blood sample from you. The healthcare professional will prick your finger or draw blood from a vein in your arm. Your blood sample will be sent to a laboratory for testing.

You can’t do it yourself. A healthcare professional conducts the antibody testing in an authorized medical facility.

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9. What are the possible results of an antibody test?

Positive result: Antibody positive test result means COVID-19 antibodies are present in your blood.

You have been infected in the past, even if you didn’t have symptoms. As mentioned earlier, the result can also be false-positive. This means antibodies detected in your blood could be another COVID-19-related virus. 

Don’t assume you are protected from COVID-19 if you have a positive result from your antibody test. Little is still known about immunity to the virus, so it’s best to continue to follow safety protocols.

Frequently wash your hands. Wear your face mask and observe social distancing, especially in public places.

Negative result: This means you probably haven’t been infected by the COVID-19 virus. You can also have a false-negative result. This can mean your blood was collected too soon and your body still didn’t develop antibodies.

Both positive and negative results can have false readings if the antibody test itself is flawed or defective.

10. How long will it take to get the result?

This depends on the medical facility. The Well Life ABQ tests both IgG and IgM antibodies and you can receive the result within 5-7 days. 

Ongoing developments:

Antibody tests will still have to undergo the process of certification with the FDA. In the meantime, it’s allowed with the EUA issued by the FDA. 

The FDA is presently collaborating with other government agencies to further study whether a positive antibody or serologic test relates to immunity against COVID-19.

This initiative aims to determine the level of antibodies required for protection from reinfection. It also includes the length of protection and the possible factors linked to the development of an antibody. Even if these are less accurate, it can still help in the containment of contagion in high-risk and densely populated areas.

Contact Us

For more details on the antibody test for COVID-19, you may call Well Life ABQ, a direct primary care provider in Albuquerque, New Mexico at 505 585 2345. You may also click on the link for detailed costs of COVID-19 antibody testing.

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