COVID-19 Testing Decoded- How Does this Work?

Since the beginning of this year, the only name we hear while we wake up and go to bed again is- coronavirus. COVID-19, the novel coronavirus disease that emerged in the city of Wuhan, China, has now spread around the globe, almost affecting more than 200 nations. As of now, 1,352,266 coronavirus cases and 75,299 deaths have already been reported, while only 287,679 people have been recovered from this deadly virus.

COVID-19 is an infection generated by the new strain of coronavirus known as SARS-CoV-2, which causes respiratory illness. This disease, which emerged from SARS-CoV-2, is like MERS (Middle East respiratory syndrome) and SARS (severe acute respiratory syndrome) since it produces severe illness, pneumonia, and even death in the extreme case. An infected body will start showing symptoms of COVID-19 in 2-14 days and might have a fever, shortness of breath, or even coughing. However, some infected people might not show any symptoms and still be infectious while spreading the virus to others.

COVID-19 Testing: What is it, and how is it carried out?

Clinical laboratories are integrating with the Centers of Disease Control and Prevention (CDC) and public health labs for testing SARS-CoV-2. With the help of testing, healthcare professionals can clearly find out about infected people who need to isolated and taken proper care. It even enables the public health staff to keep track of the virus spread. However, not all people will be found infected, and some might have only mild to moderate illness.

Since the pandemic is widening at a rapid rate, people are coming up with various questions such as- how the COVID-19 testing is performed and processed. Well, in this post, I am going to clear it in detail and understand how the testing works.

Lab testing for COVID-19 and SARS-CoV-2 virus accompanies methods that identify if the virus and antibodies are present that produced in the response of infection. The verification of the presence of the virus is confirmed by RT-PCR and the test is specifically built for detecting the RNA of the SARS-C0V-2 virus.

Detecting antibodies is used for diagnosis as well as population surveillance and the antibody test represents the number of people who have had the virus, even counting those who had minor symptoms. With this test, the specific mortality rate because of COVID-19 and the level of herd immunity can be discovered with accuracy.

How is it tested?

COVID-19 test are based on RT-PCR (reverse transcriptase polymerase chain reaction) testing for identifying the virus’s RNA in a respiratory tract sample from the sufferer. Basically, there are three methods for testing COVID-19- detecting virus from PCR test, non-PCR test, and the third is- chest CT scans and radiographs.

Let's understand all of them in detail.

Detecting virus from PCR tests

With the real-time reverse transcription polymerase chain reaction (rRTPCR), the test is carried out on respiratory samples gathered by numerous methods such as nasopharyngeal swab or sputum sample. The results can be expected in the next few hours or within the next two days. The RT-PCR test that is carried out with throat is helpful in the first week of the infection because the virus escapes from the throat and continues to spread in the lungs. For patients who are tested in the second week, a sample is taken from the deep airways by a suction catheter or using the sputum.

Early PCR tests were developed in Berlin in Jan 2020, and further, the UK developed it by 23 Jan 2020. However, Taiwan is working upon a test that makes use of a monoclonal antibody that binds to the nucleocapsid protein and is expected to give results within 15-20 minutes.

Non-PCR Tests

The FDA-approved test prepared by labs worldwide make use of nucleic acid amplification technology in place of PCR. The non-PCR test gives the results of positive cases in not more than five minutes while presenting the negative results in thirteen minutes only as it does not need the longstanding range of alternating temperature cycles. In the US, there are already 18,000 machines available and these machines can produce more than 50,000 tests every day.

Chest CT Scans and Radiographs

Chest radiographs have little significant value in the early stage, while CT features comprise of ground-glass opacificities with the asymmetric distribution. CT is more sensitive, unlike the PCR method and is less specific where the imaging functionalities overlap with other disease processes. For now, the CT method is not at all a preferable method for diagnosing COVID-19.

The healthcare professionals will swab the back of the throat, get the saliva sample, take the liquid sample from the lower respiratory tract. In the laboratory, the researchers will derive the nucleic acid that contains the virus genome. They further amplify various areas of the genome by making use of reverse transcription polymerase chain reaction. They can compare the sample with the SARS-CoV-2, which has almost 30,000 nucleotides, out of which 100 nucleotides are related to SARS-CoV-2 and these nucleotides comprise of two genes in the SARS-CoV-2 genome. If a test reports both the genes, it is considered as positive, indecisive if one is present and negative if both are absent. The positive and indecisive tests are further forwarded to Washington's Public Health Laboratories and the CDC for detailed testing.

For the US citizens, there are chances that a health professional makes use of long Q-tip for swabbing the back of the throat and take the sample to test. However, for nations like China, who already have an antibody test, the person might get blood drawn. Further, the process is different for both the scenarios- the throat swab goes for the PCR testing, whereas the blood sample is mined for antibodies specific to coronavirus.

Anyone having symptoms like cough, shortness of breath, or fever must consult a doctor right away, otherwise, things will get worse and out of control in no time. Mild symptoms even include a sore throat, tiredness, and cough that might last up to one to two weeks. The scope of risk is even wider for elderly people or who have chronic health problems. Since we know there is no vaccine declared till now to cure COVID-19, we must take precautions, stay isolated, avoid gatherings, and consult a doctor if you feel unwell at any time.