INSIDE-COVID-19-DETECTION

INSIDE COVID-19 DETECTION

 “Go to that chamber and once attended to, come back.” Where to?

And by the way, it’s not titrations or oscillations here, no  -- it’s COVID – SARS – Diagnostic Lab.  I know what comes to your mind – syringe, sample, gloves, what else? When was your last check to that white coat? It’s indisputable that to most (if not all) was after messes emanated, right? With the recent pandemic, it’s calculable that in one way or another, we might land in there. Let’s dissert through this COVID detection:-

Please review my previous article by clicking the link below to get acquainted.
(https://mentormartinke.blogspot.com/2020/03/corona-why-we-are-doing-it.html)

Diagnosing a disease – evidence based medicine -- is key to better patient management. A disease is better treated once what’s causing it is identified. Disease – abnormal body functioning. And now, this necessitates testing. SARS-CoV-2 is a new strain novel Coronavirus. Its detection, obvious through testing, has not been a walk in the park worldwide.

The following article highlights the most recent plus the gold standard testing procedures undertaken by various laboratories in different countries. Two broad categories are addressed: Molecular and Serological.

MOLECULAR METHODS:

CDC 2019-nCoV Real-Time RT-PCR Diagnostic Panel

Courtesy: CDC

Centre for Disease Control and Prevention (CDC) is an Atlanta-based institute whose mandate is to promote public health and safety through control and prevention of infectious diseases. This was the first COVID-19 testing procedure to receive Emergency Use Authorization from FDA. It’s used for the qualitative detection of SARS-CoV-2 RNA in respiratory specimens from patients who have met the clinical and epidemiological criteria stipulated by CDC and WHO.

The very first step is the extraction of nucleic acid from respiratory samples collected followed by purification. From your Form 1 biology – nucleus – An organelle that controls all body functions. Nucleic acids are two: DNA and RNA. They’re housed in this organelle. In step 1, the sample is subjected to authorized extraction methods which can either be alcohol-based or membrane-based. Step 2 – real time RT-PCR. Remember, SARS-CoV-2 contains RNA genome, and so we’ll extract the RNA. This RNA genome undergoes reverse transcription into a complementary DNA (cDNA). The cDNA is then amplified (many DNA copies) following sequential thermal cycling procedures. The DNA is rapidly increased to detectable levels using specific probes.

Courtesy: NPHL

In Kenya, all COVID-19 testing services are centralized. Testing is done at the National Influenza Centre, which is a department within the National Public Health Laboratories-KNH Complex, KEMRI, private class F referral laboratories such as Pathologists Lancet Kenya, Aga Khan University Hospital, etc. All these diagnostic centres are using this method which remains to be the gold standard test for SARS-CoV-2 recommended by CDC. This PCR diagnostic method takes 2-6hrs.

And by the way, PCR means Polymerase Chain Reaction. Generally, it involves the following: Denaturation, Annealing, and Extension. RT means Reverse Transcriptase – RNA dependent DNA Polymerase -- An enzyme which converts RNA to DNA (disobeying the Central Dogma).

For further reading:
CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel

 

CEPHEID’s Xpert Xpress SARS-CoV-2 Test

Cepheid is a US based medical diagnostic company. The Xpert Xpress SARS-CoV-2 is a rapid test for the qualitative detection of the SARS-CoV-2 nucleic acid (molecular-based) from respiratory samples either as swabs or aspirates. 

Courtesy: Cepheid

Testing using Xpert Xpress SARS-CoV-2 is however run on the GeneXpert Systems. The sample is loaded onto a cartridge and then run on a GeneXpert machine. Four samples can be run simultaneously. This method takes only 45 minutes to deliver the results. It’s also a point-of-care test with an Emergency Use Authorization (EUA) from FDA.

For further reading:
CEPHEID's Xpert Xpress SARS-CoV-2 Test

ABBOTT’s ID NOW COVID-19 System

Abbott is an Illinois-based medical and healthcare provider company. On March, 2020, this company inaugurated a rapid molecular-based SARS-CoV-2 detection method. This method has already received U.S Food and Drug Administration (FDA) Emergency Use Authorization in order to urgently help in the fight against this menace. It is the most effective method developed so far as positive results are relayed within 5 minutes. It only takes 15 minutes for negative results.

Courtesy: ABBOTT

This new invention comes following United States, a superpower, disappointment in its fight against COVID-19.  This method is set up on the ID NOW platform which is currently the most widely used molecular-based point-of-care-testing especially in the USA. The ID NOW Platform is portable, small, very accurate, and therefore it’s highly needed by the healthcare fraternity. Point-of-care testing means that patient’s results can be received right at the doctor’s room, Emergency Unit, etc. without necessarily sending the samples to the central lab. Abbott works at one single temperature as opposed to repeated thermal cycling procedures in routine PCR methods.

Here’s how it works (simplified)

1. A nasal, nasopharyngeal or oropharyngeal swab is collected for testing.
2. The collected sample is then mixed with reagents provided by the manufacturer. They disintegrate the virus in order to release the viral RNA genetic material.
3. The reagents recognize a unique section of the Coronavirus genome, while ignoring other viruses even if they are similar strains.
4. The SARS-CoV-19 viral genome is then replicated in turn making the virus more detectable. 
5. ABBOTT molecular test reads and displays the result to the healthcare personnel present.

From April 1, ABBOTT diagnostic company began shipping about 50,000 ID NOW COVID-19 diagnostic gadgets per day globally.

For further reading:
ABBOTT's ID NOW COVID-19 Test

Other rapid molecular methods include:

1. Cobas SARS-CoV-2 by Roche Molecular Systems (RMS)
2. Simplexa COVID-19 Direct Assay by DiaSorin Molecular LLC
3. TaqPath SARS-CoV-Assay by Quidel Corporation
4. PerkinElmer New Coronavirus Nucleic Acid Detection Kit by PerkinElmer Inc.
5. Lyra SARS-CoV-2 Assay by Quidel Corporatic
6. Biofire COVID-19 Test by BioFire Defense, LLC
7. COV-19 IDX Assay by Ipsum Diagnostic, LLC
8. COVID-19 RT-PCR Test by LabCorp

It is worth noting that these methods outlined above have a geographical limitation.

SEROLOGICAL METHODS:

SARS-CoV-2 IgG/IgM Rapid Test

This diagnostic method was developed by Cellex -- a North Carolina based biotechnology company. This is a rapid test for the qualitative detection of IgM and IgG antibodies against SARS-CoV-2 in whole blood, plasma, and serum from individuals showing clinical signs and symptoms of COVID-19 disease plus epidemiological factors such as geography, exposure, etc.

Courtesy: BioMedomics

Once your body is exposed to foreign substances, it develops an immune response – fight against ‘incoming outsiders’. These foreign substances are called antigens, right? Now, the body develops certain protein molecules called antibodies to eradicate these antigens from your body. Following exposure to SARS-CoV-2 virus, the body recognizes them as foreign, and in turn, develops antibodies to clear them. Immunoglobulin Mu (IgM) is the first antibody to develop after initial infection while Immunoglobulin Gamma (IgG) develops later following infection.

The test cassette has both IgM and IgG bands in order to increase the test’s sensitivity and effectiveness. Remember, concentration or antigen-antibody ratio is a very critical factor influencing serological reactions. And therefore molecular methods remain to be more effective to this serological method.  Actually, only certified laboratories under the Clinical Laboratory Improvement Ammendments of 1988 (CLIA) are allowed to perform this diagnostic test.

For further reading:

qSARS-CoV-2 IgG/IgM Rapid Test

CONCLUSION

Molecular testing remains to be the gold standard method for COVID-19 diagnosis. We all need to salute all the molecular biologists, virologists, epidemiologists, microbiologists, and the medical laboratory scientists at large for this critical diagnostic role. Early detection is key to better diagnosis and management. So in case of any clinical signs such as dry cough, dyspnea, fever, headache, etc, have a ‘date’ with a healthcare provider. And together, we shall overcome.

Welcome to my next blog post. THANK YOU!

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