May 24, 2020

Coronavirus Special Series

COVID-19 Tests Explained | for Dummies

Flattening the curve! We need more tests! We need vaccine! COVID-19 is affecting everyone of us by now. Ironically most of us are not affected by the virus but the fear surrounding this virus and the uncertainties of our lives going forward – social distancing, lockdown, confinement, movement control, borders closed, loss of jobs and company closures, economic recessions, class suspension, just to name a few. Everyone has been saying mass testing is the only way to end the lockdown (If no vaccine is invented yet). But what exactly are those Coronavirus tests? One day I saw on the news – Team Japan develops 10-minute coronavirus test; Another day another news broke out Singapore researchers invent Covid-19 test that can tell if someone’s infected in 5 minutes; Another day again I saw – Taiwan develops rapid 10-min Ab test kit for COVID-19. I don’t know about you but I got even more confused the more I read. How many tests are there for COVID-19?

Naturopathic Medicine | Endocrine | The Clinic of Natural Medicine

How many kind of testing techniques are currently being used or invented? How do they work? There are so many question marks and I decided to read through everything I can find online and do a compilation of those tests being used and being developed for easy understanding for layman like us. Here’s my summary.

**Disclaimer: The following summary is an attempt to simplify the information of various tests currently running for COVID-19 based on my quick research. If there is any inaccuracy or discrepancy, feel free to let me know and I’m happy to make amendment. My contact details are below.

1 – Polymerise Chain Reaction (PCR) Test

At the moment the majority of the current Covid-19 tests that all the reports are coming from are using PCR” ~ says University of Sussex senior lecturer in microbiology Dr Edward Wright.

The swab tests we have been hearing about on the news to count for the confirmed cases are mostly used for PCR Test. So before we talk about PCR test, you should know what is a swab test.

Swab Test

Home tests for coronavirus not yet approved by FDA - The ...

Photo Credit: Washington Post

To collect the sample testing tissue using swab. Normally the swab goes into our nasal or throat to collect the sputum (a mixture of saliva and mucus produced as a result of infection) where the tissues were extracted. Hence sometimes it’s also called nasal test or sputum test (though they can refer to totally different things in the specific medical terms)

What does PCR Test do? 

– To diagnose an active COVID-19 infection, i.e.to see if someone is infected or carrying the virus in the body NOW. It’s mainly used to confirm the positive COVID-19 cases.

How? 

– Use the tissue collected from Swab test. Then match it with the genetic information of the virus (RNA). If the result is positive, you are a virus carrier! If you are interested to know how do the test actually works, you can read the article here.

This is a quick Infographic Summary of PCR Test by American Society of Microbiology

Advantages of PCR Test

– Most accurate test so far

– Tell us who has the virus NOW

Disadvantages of PCR Test

– Slow. Analyzing the results take 2-5 hours (Some places take up to 1-2 days).

– Labor intensive. Many stages (errors may occur between sampling and analysis). False negatives can occur up to 30% of the time with different PCR tests because of these multiple stages of analysis required.

Main Concern 

False negatives – meaning if you get negative results from PCR test, don’t be happy too early. There is up to 30% chance that you might have the virus. Just the test couldn’t tell it. So you might still be quarantined. It’s not an “all-clear” for you.

Other terms used for PCR Test

– Genomic detection-based (molecular test)

– Molecular diagnostic testing technique

– Genetic Material Test

2 – Antibody Test

Fergus Walsh: ‘I was gobsmacked to test positive for coronavirus antibodies’ ~ BBC reported on Antibody Test rolling out in the UK to NHS and care staff on 23 May 2020

The blood tests for COVID-19 are mostly about antibody test. So before we talk about Antibody test, you should know what is a blood test.

Blood Test

Scientists develop the first blood test for melanoma detection

Photo Credit: biospectrumasia

To collect the sample testing tissue from blood. Normally a small sample of blood is drawn from your arm using a needle or a finger prick to collect the serology (blood serum) for various testing analysis. Hence sometimes it’s also called serology test as well.

By the way, when you talk about the blood test, most people in start-up would immediately recall the “bad blood” book written by John Carreyrou documenting about the meteoric rise and shocking collapse of Theranos, the multibillion-dollar biotech startup who wanted to use a blood test to change the world.

Out of topic. But thought it’s something about blood test that’s worth sharing.

What does Antibody Test do? 

– To diagnose past or recent COVID-19 infection, i.e. to see if someone had been infected before by analyzing if the person have the antibody of the virus in the body. It won’t tell you if you are infected currently, but it tells you if you have been infected and you are immune to the virus. Antibodies for the Coronavirus are generated by our body’s immune system normally after 1-2 weeks to clear the virus from our body. An antibody test is used by the research institutions and government agencies mainly to determine the populations of people who had been infected before to determine if it is possible to achieve herd immunity (i.e. if there’s more than 90% population who have immunity, then the virus won’t spread even if a small proportion of population are infected. Think Chicken-pox or Measles). The test is also used by a research team at Duke-NUS Medical School to do contact tracing

How? 

– Use the plasma collected from blood/serum test. Then add antigen (see #3 Antigen test) and wait for about 10-15 minutes for the reaction. If the result is positive, you have the antibody of Coronavirus in your body. The bad news: You just recently had COVID-19! The good news: Your body had produced the antibody that fight off the virus! Your survival rate is high or you might have been cleared of the virus by now! If you are interested to know how do the test actually works, you can read the article here.

This is a quick Infographic Summary of Antibody Test by American Society of Microbiology

Advantages of Antibody Test

– Fast (10-15 minutes for the result)

– Might be able to do at home in the future (Like a pregnancy test). Japan will be selling the test kits.

– It tell us if we have the antibody to the virus (Meaning: have certain immunity to the virus!)

– It tells us what proportion of the population are theoretically immune to the virus, the information could help lift the social distancing restrictions on movement.

Disadvantages of Antibody Test

– Accuracy – Some people who have been infected with the virus didn’t develop any immunity at all. Meaning they would be tested negative for the antibody test, i.e. from the test result they thought they don’t have COVID-19, but they actually have it, just that there is no antibody in their body! It’s not exactly what we want isn’t it? Imagine when you get the “Negative result”, it doesn’t mean you don’t have Covid-19, It only means you don’t have the antibody in your body. You might have it but your body hasn’t produced the antibody yet.

Main Concern 

False positive – meaning if you get positive results from Antibody test, you might thought “Yay I have immunity” but you are not. Currently it’s unclear how much antibody is needed to give you the immunity or how long the antibody will last in your body. There had been reports of COVID-19 Patients Test Positive After Recovery in South Korea.

Other terms used for Antibody Test

  • Immunoglobulin detection-based (serology) test
  • IgM Test – IgM is usually the first, specific antibody type generated by the body in response to infection. 
  • IgG Test – IgG antibody type is generated after IgM and replaces IgM as the predominant antibody in the response to infection. 

Here’s a youtube video I found explaining about the 2 different tests

#3 Antigen Tests

On May 9, 2020, the US Food and Drug Administration (FDA) issued an emergency approval for an antigen test to help identify those with COVID-19. The rapid test—officially known as the Sofia 2 SARS Antigen FIA, created by the Quidel Corporation in San Diego—promises to “quickly detect fragments of proteins found on or within the virus by testing samples collected from the nasal cavity using swabs,” according to the FDA. Read from health.com

What is Antigen?

A quick google search give me this result – According to US National Library of Medicine, an antigen is any substance that causes your immune system to produce antibodies against it. This means your immune system does not recognize the substance, and is trying to fight it off. An antigen may be a substance from the environment, such as chemicals, bacteria, viruses, or pollen. An antigen may also form inside the body.

What does Antigen Test do? 

– To diagnose an active COVID-19 infection like the PCR Test mentioned in #1

How? 

Use the tissue collected from Swab test and the diagnostic quickly detect the presence of the nucleocapsid protein, part of the SARS-CoV-2 virus (that causes COVID-19).  If you are interested to know how more about the test, you can read the article here.

Advantage: Fast (~15 minutes)

Disadvantage: May not detect all active infections. Higher chance of false negative than PCR test.

— Conclusion —

So, most of the news we read — those 10-minutes or 5-minutes COVID-19 tests being developed by different companies, they are either antibody test or antigen tests. High speed but questionable accuracy.

I hope the compilation of the tests available for COVID-19 is useful for your understanding.

It’s worth noting that none of them are perfectly accurate and hence it’s hard to contain COVID-19 till now. 

I am just a layman reading the news and hoping for the end of the pandemic soon. Please continue to stay home, stay healthy, and stay productive.

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