Hello again, everyone. This is Dr. Ali Raddaoui, owner and founder of I am encouraged by your comments and questions about the first interview with Dr. Rayane Rafei on the Coronavirus. While it seems the virus is slowly receding from people’s and media outlets’ radars, there are places that continue to be hotspots, and so, vigilance remains the order of business for the foreseeable future. Dr. Rayane Rafei is a renowned Lebanese microbiologist with over 20 articles published in internationally peer-reviewed journals, and I have the ultimate pleasure to host her again in this post.

1. Ali: Welcome again, Dr. Rayane Rafei. We’re continuning our conversation of a few ago on how the Coronavirus is rolling out. There are still lingering questions that I would like you to address. What are the different ways used to ascertain that a person is definitely a bearer of COVID-19?

Image courtesy of United Nations COVID-19 Response

Rayane: Before delving into diagnostic techniques, let’s dissect simply the biology of the SARS-CoV-2 virus causing the COVID-19 disease. The SARS-CoV-2 is composed of considerably long genetic material (precisely RNA), and proteins. To ascertain that a person is a bearer of the virus, a diagnostic test of COVID-19 disease can target some of these different biological components of the virus. First, a respiratory sample should be taken from the suspected person by a trained laboratory person. Usually, the respiratory specimen is a nasopharyngeal swab, something that passes gently from the nose to what feels like the bottom of the eyeball.

But the sample doesn’t have to be a nasopharyngeal swab; it could be something else such as saliva or blood. Once we’re in possession of a sample, it should be tested for the presence of the virus.

3. Ali: What is the current gold standard in ascertaining that a person is actually infected?

Rayane: The gold standard COVID-19 diagnostic test (recommended by the World Health Organization (WHO)) is a technique known as RT-PCR. This stands for Reverse Transcription-PCR. This technique has the capacity to detect a small amount of viral genetic material (the viral RNA). The test should specifically be interpreted to mean that when it comes back positive, it is almost certain that the suspected person has the

SWAB TEST. Patient and medical supervisor

preparing for a COVID-19 nasal swab test. Image

created by Russell Tate. Submitted for United

Nations Global Call Out To Creatives - help stop the

spread of COVID-19.

infection. What we got to say, though is that the test is not sufficiently sensitive, meaning that when the test comes back negative, the person is probably not infected at the time the sample was collected. This time around, we might say unfortunately that the gold standard is not so golden.

4. Ali: What is causing this confusion?

Rayane: Many factors lie behind negative tests in persons carrying the virus under real-life conditions. This is what we call a “false-negative result”, which simply means that even though the result is negative, meaning that the person is not infected, in fact, that person is a carrier of the virus. The reasons may have to do with inadequate sampling, laboratory techniques, or the very substances used in the test. To compound this confusion, a person may actually be infected by many respiratory pathogens as the flu, SARS-CoV-2, and others. In medical parlance, this is called “co-infection”. What happens is that this test can yield a negative result as the genetic material of SARS-CoV-2 may be masked by other respiratory pathogens.

5. Ali: What’s the right course of action in such cases?

Rayane: In principle, that’s easy. What is required in such cases to re-test especially for persons with a suspicious clinical history. By this I mean persons who have had close contact with infected persons or others who are residing or traveling to regions designated as hotspots. Clinical history that calls for retesting also includes the presence of symptoms such as fever, dry cough, and breath shortness.

6. Ali: What other techniques are available to determine infection?

Rayane: Quite a few, though still under medical investigation. For example, there are other diagnostic tests known as serological tests. These are specifically designed to detect antibodies developed against SARS-CoV-2 by the immune system of an infected person during the second or third week of infection. There are now many rapid tests referred to as point-of-care testing, POCT for short. Some of these are able to detect either the viral proteins or human antibodies produced in response to infections. They can produce results in as little as 15 minutes, and a medical decision should follow, on the spot, there and then, based on the result. To date though, these tests are recommended research purposes, and not for a clinical decision, which means we do not yet have enough evidence of reliable performance.

I can’t stress enough that serological tests are very important because many people carrying the virus remain asymptomatic. For example, when tested in a large community, we can get a clear snapshot to see who has potentially developed immunity against the virus and who remains vulnerable to it. Therefore, these tests are highly appropriate for the public health ministries to assess immunity against the COVID-19 virus at the community level and to see if we are on the way to the so-called herd immunity. These tests can also help ministries to critically evaluate the physical social distancing measures implemented to combat the virus and to tighten or mitigate the disease.

7. Ali: Is there one preferred method for diagnosing COVID-19?

Rayane: The truth of the matter is that no one foolproof method should be solely relied upon as the medical profession is still in the process of learning about this virus. Because of this, diagnosis of COVID-19 should be based on a combination of criteria including case history, clinical symptoms, the results of diagnostic tests, and also the radiological analysis of chest. We have come a long in understanding the various processes of infection, propagation, testing, vaccination, and medication, but there is a lot more to be learned about COVID-19.

8. Ali: Thank you, Dr. Rayane, for being my guest today.

Rayane: Thank you for hosting me.

Dr. Rayane RAFEI is an Assistant Professor at the Faculty of Public Health at the Lebanese University. In 2014, she holds a doctorate in microbiology from the Lebanese University and the University of Angers in France. She belongs to the team of the Laboratoire de microbiologie, santé et Environment (LMSE) affiliated to Doctoral School for Science and Technology, and Faculty of Public Health at the Lebanese University. To date, Rayane published more than 20 articles in internationally peer-reviewed journals. She can be reached at

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