The Top 4 Different Coronavirus Tests With Their Strengths and Limitation

Coronavirus is a deadly virus that has already claimed millions of lives worldwide. There is no stopping or halting the outbreak of the global pandemic. It is still spreading undefeated, and precautionary measures are essential to prevent the spread of the COVID-19 virus.

If you are feeling the symptoms of a common cold, respiratory issues, and other severe conditions, it is better to get yourself tested. But how do you identify the best test from a list of different options available for testing labs? 

Table of Content

Some Common Symptoms Of the Coronavirus

COVID-19 Test: A Dire Necessity

The 4 Different COVID-19 Tests

Conclusion

In this blog, we will discuss the four main types of test that can identify signs of COVID present in the human body. We will try to explain their strengths and limitations along with some information so that you can get an idea of what test to choose when battling the pandemic. 

Let us begin by understanding when you need the test and how to determine that you might have a coronavirus infection. 

 Some Common Symptoms Of the Coronavirus

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Coronavirus (or COVID-19) is a type of virus that causes respiratory infections in humans. The symptoms for it may differ from a mild cold to other symptoms that may require serious hospitalization. Identifying the virus when it is present in an individual is vitally important for any treatment to be effective as the vaccine is in scarcity. 

Here is a list of symptoms that are common amongst coronavirus patients:

Body ache

Headache

Sore throat

Dry cough

Fever

Loss of smell and taste

Fatigue

Vomiting

Nausea

Coronavirus is especially dangerous for people who already have an underlying condition. This may include diabetes, liver or kidney disease, asthma, obesity, high blood pressure, cancer, heart disease, and other similar conditions.

COVID-19 Test: A Dire Necessity

If you are feeling any of the above symptoms, it is important to get yourself tested. The positive and negative results will determine whether you have contracted the virus. It is very important to self-isolate and to get the right treatment once you know that you have the coronavirus.

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The 4 Different COVID-19 Tests

There are different methods of testing for the coronavirus. Each has its benefits and limitations. Here is a list of those commonly used tests currently popular in the market:

I) RT-PCR

It is short for real-time polymerase chain reaction test and it is most commonly used for testing coronavirus. PCR is a process that traces out genetic material from a specific pathogen if it is present in the body. The technique can easily identify both the RNA and DNA of bacterias and viruses.

A PCR captures specific genes from genetic material within a swab sample. Then, the test multiplies it to ensure that there is enough sample to conduct the analysis. The test uses a series of chemical processes so that even the slightest presence of the virus is detectable using fluorescent dyes.

Some viruses only contain RNA that enters human cells and uses its RNA to multiply and replicate. To detect such as RNA, the test uses the ‘reverse transcription’ method. It allows a single molecule of DNA to be amplified exponentially so that even single digits of virus particles are identifiable easily.

Benefits of RT-PCR Test

  • Quick, Specific, and Sensitive: Some variations of the RT–PCR can deliver a reliable diagnosis in three hours. It is fast, super sensitive, and specific. You will get a definitive report about your infection in a day or two at max.
  • More Accurate and Reliable: This test is much faster and less likely to have errors or chances of contamination during the testing process. The lab technicians carry the entire test out in an enclosed tube, inside a specialised, automated machine. It is the most accurate test we have to detect the COVID-19 virus.

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  • Determine Severity Of Infection: The standard real-time RT–PCR set-up usually goes through 35 cycles. This means that there will be 35 billion new copies of the viral DNA created from each strand in a swab sample. This leads to better detection and easier determination of the severity of the infection.

Limitations of RT-PCR Test

  • Detects Ongoing Infection: The RT-PCR test is only efficient in determining whether the human has an ongoing infection. It cannot show the history of the patient, which can be useful to understand the spread and development of the virus. 

We need other methods to detect, study, and track past infections, especially if a patient is showing no symptoms. One can never figure out whether they ever gained the disease just because they have self-isolated themselves because of mild and unclear symptoms.

  • Requires Special Equipment and Training: The RT-PCR test is more refined and requires specific instruments in a laboratory to complete it. Despite the actual test takes no less than a few hours, there are multiple processes involved in the process that may take time. Right from getting the sample to the lab, labelling it, transporting it, and finishing the test, which may take days to identify the actual results.

The RT-PCR test machines are highly sensitive and require special training to avoid any misuse. There are limited skilled professionals in using the equipment. Each requires special training before using these advanced instruments.

  • No Quality Guarantee: In dire times of the pandemic, even the best equipment fails, as there are thousands of tests being conducted each day. The quality of results depends on the skills of the lab technicians and facilities. 

There have been several occasions where the RT-PCR test has shown false-positive results. Experts have called on quality control teams to assess the PCR testing in many locations in India and abroad. 

II) COVID-19 Antigen Tests

This is another type of COVID-19 detection test that can give results within 30 minutes. It tests the presence of a foreign protein only found in the coronavirus. In the case of COVID-19, it is the ‘spike protein’ that is present on the surface of the coronavirus. 

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The test involves taking a swab from the nose where there is a high likelihood of the presence of the virus. Then the technician dips the swap in a solution that inactivates the virus. Next, they transfer the solution to a test strip. The strip contains antibodies that bind with the coronavirus proteins and hold them in place as the liquid spreads.

If the patient has the coronavirus, coloured lines will appear in the paper strip within the next 15 to 20 minutes. 

Benefits of Antigen Testing

  • A Better Alternative: There are lots of times where antigen testing proves a better alternative to RT-PCR tests. No more institutes have to rely on just one test to confirm many cases that can come out as positive within the first 20 minutes of testing.
  • Highly Useful: It is fast and less sensitive. It can conclude a definite positive within minutes. It can be highly useful in places with high crowds undergoing testing and identifying ones with infection faster. This way the patients who test positive can undergo isolation quicker.
  • Less Expensive: The cost of antigen testing is much less than compared to RT-PCR tests.

Limitations of Antigen Testing

  • Cannot Depict Past Diagnosis: The Antigen test only lets you know if a person has recently contracted the coronavirus. It cannot be used to identify any infections in the past, as the antigens won’t be present in the body during testing.
  • Inadequate Sample Space: There are chances that the virus is present in single digits in a human body. It is difficult to determine its presence through antigen testing. 

There have been several cases where this test provides a false negative result. Specialists highly recommend following a negative test with a more accurate RT-PCR test to confirm a true negative for coronavirus. 

  • Lacks Accuracy: This is the major problem that antigen testing is facing today. The test is much less sensitive than the RT-PCR test and is less accurate, making it highly unreliable.

III) Antibody Tests

It is a type of COVID-19 test that tests for antibodies in a patient’s bloodstream. We also know it as ‘serological testing’. It can determine whether an individual has the coronavirus. 

The human body generates a specific type of antibody to defend itself against infections. They are unique for each disease and the same goes for coronavirus. The antibodies may be still in the bloodstream that antibody tests can detect. However, it is not useful to show whether the virus is currently infecting the body. 

Unlike nasal and throat swab tests, the antibody test samples the blood through a finger prick or drawn from a needle. It looks for traces of the body’s response to the virus. The test looks for IgM antibodies that develop early in the SARS-CoV-2 infection and IgG antibodies found after someone has recovered from the infection.

Benefits of Antibody Tests

  • Helps Estimate Gravity of Infection: There is no way to estimate how dire the situation is because of widespread infection of the coronavirus. The antibody test gives the authorities an idea about the COVID-19 status.

The test provides researchers and institutions with an estimate of the rate of infection. This helps to determine how fast the virus will spread and precautions to take. 

  • Helps Determine Susceptible Patients: The antibody test also offers information on what factors affect the severity of infection. It also lets authorities know why some people are more severely affected than others. 

Limitations of Antibody Tests

  • High margin of Error: The antibody test is useful in establishing who has had the virus, especially where people are asymptomatic and show no symptoms. The test shows result within half an hour. It is useful to establish who has had the virus, but it has a large scope of error than swab tests.

The finger prick test to look for IgM antibodies is rapid and can give results within 30 minutes. However, the IgG tests require samples to be sent to the lab – which can take weeks to deliver results. The IgG tests are more reliable than IgM tests. However, they do not reveal as much information about someone’s COVID-19 infection.

  • False Results: There are high chances that the antibody test can be inaccurate, resulting in false positives and false negatives. Most test kits result from fast-tracking approval and outrageous demands. Here the priority is speed and not public health.

This results in some kits performing better than others. There is no assurance or guarantee that the test results will be 100% accurate. Sometimes, individuals do not develop antibodies after infection resulting in ‘false negative’. In other cases, the test may show a ‘false positive’ if the patient has contracted a similar virus.

  • A Lot of Inaccuracies: The accuracy of antibody tests highly decreases as time passes. We know it takes almost 2-3 weeks for antibodies to generate in the human body. This results in high inaccuracies in the results, especially if there are no symptoms in the body.
  • False Assurances: The incorrect result may make a person feel secure about their health, but it may be not so. This is a serious case where the health of those around the patient becomes high risk, especially if there are senior citizens involved.

IV) TrueNAT Testing – Where Quality Meets Quantity

This is the ultimate true detection test for coronavirus. It is a portable, chip-based RT-PCR machine developed by a Goa-based startup, Molbio Diagnostics. The TrueNAT test was initially designed for diagnosing tuberculosis. It has since been proven effective in detecting a wide range of pathogens in real-time.

The device is highly reliable and recommended by many public health authorities. It is the fastest PCR-based testing technique to fight coronavirus in many countries. Its usage depends from country to country.

The machine can detect an enzyme (called RdRp) present in the RNA of the coronavirus SARS-CoV-2. It is a conclusory method of confirming the presence of the COVID-19 virus in an individual. 

Conclusion

Many countries rely on PCR-based testing as they are reliable and fast. Antibody testing is still an efficient, affordable, and scalable option. It has been used by many countries to test for coronavirus and get quick results. There is still ongoing research on better and reliable test kits. Authorities are making their best efforts to check coronavirus by improving the quality of testing procedures. We are still a long way from winning with the pandemic. You must be aware of all the tests available in the market to protect yourself and your loved ones.  

Aakansha Bhatnagar

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