Rapid Test Kit for COVID-19

Hello, galaxy brainers! Welcome to my new entry!

Currently, the Covid-19 pandemic has been a serious global issue since 2019 and has affected many lives. The pandemic has been going on for a year and yet there's still no reliable vaccine that can be used to suppress the virus. More that, with the constant raising in the number of infected lives- scientists are progressively finding and creating effective rapid test kit to accurately identify the ones who are infected.

Before we start, allow me to introduce to you the name of this mysterious virus-

SARS-CoV-2 is the virus that attacks the human immune system or lymphocytes (white blood cells) to take down the host (humans).

Since SARS-CoV-2 is still mysterious to all of us, it has been really challenging for the scientist to create a rapid test kit to detect the virus because-

1. The virus is still novel. The scientists need to understand its biological structure.

The virus is able to mutate into several forms.

If you are interested to read more on the challenges of creating a rapid test kit for Covid-19, please click the link below:

• https://www.bbc.com/future/article/20200422-why-are-coronavirus-tests-so-difficult-to-produce

ANYWAYS, WE HAVE A BIG QUESTION TO ASK-

WHAT'S A RAPID TEST KIT?

It's a simple tool that can detect (qualitatively/quantitatively) to determine the results instantly.

In simpler words,

• Qualitative gives a yes/no results- For example: a pregnancy test kit that can only verify whether someone is pregnant or not.

• Quantitative gives detailed information, yes/no results and the amount, concentration of the tested component.

An example of a qualitative test kit and how it works to test for Covid-19

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Apparently, there are three types of rapid test kit available in the market for Covid-19 detection that are:

1. Molecular test

2. Antigen test

3. Antibody test/Serology test

Today, we are going to dig more about the antigen and antibody test kit.

Before we go deeper into the test kit, let's try to understand what SARS-CoV-2 is.

The overview of SARS-CoV-2

SARS-CoV-2 stands for Severe Acute Respiratory Syndrome Coronavirus 2 that is classified under the family of Coronaviridae. The virus has 4 structural proteins that are:

1. Membrane (M)

2. Spike (S)

3. Nucleocapsid (N)

4. Envelope (E)

Figure 1 The biology structure of SARS-CoV-2

SARS holds similar features as Human Immunodeficiency Virus (HIV) that both viruses have:

1. Spike (S) glycoprotein to infect the host

2. The oval shape of the nucleocapsid (N)

I found from a journal that the incorporation of HIV and SARS can produce virus-like particles (VLP). Check on the link below if you are interested to know more about it-

• https://pubmed.ncbi.nlm.nih.gov/18592403/

Well, enough with the introduction to SARS-CoV-2. Let's head on to the next topic that is

• Antigen Rapid Test Kit

• Antibody Test Kit

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The Antigen Rapid Test Kit

What's Antigen?

Let's draw an illustration of what an antigen looks like

• The antigen is a molecule that usually made up of proteins, polysaccharides, lipids, and nucleic acids.

• Antigen has the capability to stimulate the immune system.

• Different antigen has different features that can be recognized by its particular antibody.

SARS-CoV-2 has several known antigens that are known as the 4 structural proteins as illustrated in Figure 1. These antigens are visible protrusions on the surface of the virus.

Antigen and antibody is related to one another. Like a lock-and-key mechanism. A specific antigen can only fit to its specific antibody.

As shown in the figure below

• Just like lock and key, a specific key can only unlock its specific lock. A different antibody can fit different antigens to eliminate them.

The concept of Antigen Test

• A rapid diagnostic/qualitative test

• The test is performed by recognizing specific structural or functional protein component of the virus

• It will provide a yes/no results- whether the patient is infected/not infected

• This test would require a minimum concentration of antigens that needs to be bound with specific antibodies before signalling the results

• The antigen test is completed to identify whether the patient has an active infection of the virus.

• The detection using an antigen kit is known as a rapid diagnostic test where the sample is taken from nasal or throat swab on the patient.

• The results are usually available around an hour or less which is faster compared to the antibody test.

Can you guess what type of test was done on the patient shown in the figure below?

The procedure of Antigen Test

The diagram is courtesy of

• https://diagnostics.roche.com/global/en/products/params/sars-cov-2-rapid-antigen-test.html

Advantages of Antigen Test

• Fast response compared to antibody test kit, takes an hour or less to show results

• Positive results are highly accurate

Limitations of Antigen Test

• Has lower sensitivity

• Negative results require confirmation test using a molecular test

• Has a higher chance of missing an active infection

The Antigen Test Kit for Covid-19

These are some of the antigen rapid test kits that are available on the market:

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The Antibody Test Kit

What's Antibody?

• The antibody is a Y-shaped protein structure produced by B cells of the immune system.

• Each tip of the antibody contains antigen-binding sites to bind to a specific antigen.

• The binding allows the elimination of antigen by either neutralization or "tagging"

• Antibody acts like a shield that protects a human body against pathogens (the bad guys: virus, bacteria)

Illustration of an antibody and its antigen-binding sites

The concept of Antibody Test

• The antibody test identifies whether the patient has been exposed to infection (past infection) by detecting the availability of antibodies in the blood or serum.

• The detection of antibodies can only be done after the patient's body has developed the antibodies, this may take around two weeks after the infection.

• There are two types of antibodies produced that are IgM that produces around two weeks after the infection and IgG that produces at the third week of the infection.

• The results are available around 1-3 days after the sample is taken from the patient.

• The test is able to provide information about the phase of the infection and the infection period of the patient has been infected by the SARS-CoV-2

The procedure of Antibody Test

The diagram is courtesy of

• https://diagnostics.roche.com/global/en/products/params/sars-cov-2-rapid-antibody-test.html

Advantages of Antibody Test

• Shows precise results since the sample is taken from blood, serum, and plasma

• Requires no special equipment for detection

• Simple detection kit, user-friendly (like a pregnancy test)

Limitations of Antibody Test

• May show negative results of an active infection patient; if the detection is done before the production of antibodies

• Slower result response when compared to an antigen test kit; takes 1-3 days to obtain results

• Requires for follow up test for accurate results

• May show false-positive results due to cross-reactivity with antibodies from the previous infection with other coronaviruses

The Antibody Test Kit for Covid-19

These are some of the antibody rapid test kits that are available on the market:

The information was obtained from

• https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/eua-authorized-serology-test-performance

Feel free to watch this video to obtain more information about rapid test kits for Covid-19

• https://youtu.be/5hu7_xIsCRg

Till then, be safe wherever you are and be kind to whoever you meet. And guys, don't forget to wear a mask and wash your hands frequently! Together we can win the battle against this virus!