The outbreak of the novel COVID-19 is an epidemiological threat to the nations. The techniques are available to diagnose COVID-19 alerts the countries to curb the spread quickly. Many fake news or misconceptions about the techniques and testing kits could mislead the information and health concerns extending to economic crises.
- Nucleic acid
amplification test (NAAT) - real-time
reverse-transcriptase–polymerase-chain-reaction (RT-PCR)
- Serological (Antibodies) testing
- Chest radiograph or computed tomography (CT)
World Health Organization standardized the biochemical methods like RT-PCR and serological tests to diagnose COVID-19 as of February 2020. However, research studies confirmed that image analysis could be an advent methodology to assess the infected patient.
Amidst, RT-PCR stands out for the accurate detection of the novel coronavirus (SARS-nCoV-2). Many countries are preparing RT-PCR or mini-RT-PCR kits for fast accessing of the diagnosis results. Due to the high numbers of spreading, nations rely on other tests like antibodies or CT-Scan. However, it is mandatory to confirm through RT-PCR test to declare the patient is infected or not by SARS-nCoV-2.
NAAT (RT-PCR)
It is the method based on the detection of unique sequences of COVID-19 virus RNA using a nucleic acid amplification test. Real-time reverse-transcription polymerase chain reaction (RT-PCR) is used to detect specific viral genes of COVID-19. It includes three stages, such as extraction, amplification, and analysis. Extraction of nucleic acids from the assay of nasal, pharyngeal swab specimens are employed to identify specific genes for the confirmation of infection.
Pneumonia based severe acute respiratory pandemic diseases (SARS-nCoV-2) have a 70% similarity of its genome with the previous version of SARS-coronavirus. From the knowledge index, RT-PCR assay was prepared to inspect and distinguish the novel coronavirus from other types of coronavirus such as alphacoronaviruses, betacoronaviruses, and middle east respiratory syndrome-related coronavirus. WHO conducted cross-verification tests with known respiratory viruses and bacteria in clinical samples before confirming the standardization of testing kits.
Finally, WHO recommended three types of genes for the confirmation of SARS-nCoV-2 genomic RNA as a positive control.
- First-line screening assay: E gene assay
- Confirmatory assay: RdRp gene assay
- Additional confirmatory assay: N gene assay
Most of the testing kits are based on the assay for one or any two genes. Compared to one, testing for two gene assays will result in most confirmative reliable data due to the practical difficulties like sampling, testing conditions, etc.
 |
Image credit: WHO (RT-PCR assays, Berlin, Jan 13, 2020)
|
Serological (Antibodies) test
It is an indirect method considered as a secondary test
protocol. The measurement of specific antibodies related to an immune response
of COVID-19 in the blood (serum) samples. Compared to the RT-PCR test, it is rapid
to analyze. The testing of SARS-nCoV-19 antibodies IgG and IgM from whole
blood, plasma, or serum are commercially available rapid diagnostic kits.
CT Scan
Chest radiograph or CT scanning is becoming an advised tool
for the diagnosis of COVID-19. After the investigation of 1014 patients in
Wuhan, China, from Jan 6 to Feb 6, 2020, the author(s) had concluded CT scan
could be a methodology to assess the infected patients. Results published in
the
Radiology
journal confirmed the consistency of chest CT scan analysis with the
standard RT-PCR testing. The statistical results of CT scan analysis have
higher sensitivity than RT-PCR test values.
“Chest CT may be considered as a primary tool for the current
COVID-19 detection in epidemic areas.” – Tao Ai et al., Radiology, 2020; 200642 DOI: 10.1148/radiol.2020200642
Similarly, American Roentgen Ray Society acknowledged in a recent
publication that, chest CT scan is reliable with a low rate of misdiagnosis (3.9%)
that could help for the rapid diagnosis of COVID-19. But CT scan images of
other respiratory syndrome diseases might overlap with COVID-19 symptoms.
Hence, it is mandatory to get an opinion from 2-3 radiologists or doctors with a
history of patients.
“We found that chest CT had a low rate of missed diagnosis of
COVID-19 (3.9%, 2/51) and may be useful as a standard method for the rapid
diagnosis of COVID-19 to optimize the management of patients. However, CT is
still limited to identifying specific viruses and distinguishing between
viruses.” - Yan Li & Liming Xia, Tongji Hospital, Wuhan, China. American
Journal of Roentgenology: 1-7. DOI: 10.2214/AJR.20.22954
- Ground-glass opacities (GGOs) and consolidation
with or without vascular enlargement
- Interlobular septal thickening
- Air bronchogram sign
Outlook
Resources
World Health Organization – clinical guidelinesWorld Health Organization – RT-PCR assays Differences and similarities between Severe Acute Respiratory Syndrome (SARS)-CoronaVirus (CoV) and SARS-CoV-2. Would a rose by another name smell as sweet?Correlation of Chest CT and RT-PCR Testing in Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 CasesCoronavirus Disease 2019 (COVID-19): Role of Chest CT in Diagnosis and ManagementSerology testRapid diagnostic kit for COVID-19
Author(s)
Prabakaran Shankar holds a Ph.D. in Materials Science and is a postdoctoral researcher. As a writer, interested in an analysis of the subject from a different perspective.
Lakshmishri Prabakaran holds a Ph.D in Nanoscience and Technology and is a scientific researcher interested in exploring, and writing different styles of journals.
Superb
ReplyDeleteGood info
ReplyDeletevery interesting post.this is my first time visit here.i found so mmany interesting stuff in your blog especially its discussion..thanks for the post! lanyards to buy
ReplyDeleteI truly appreciate this blog. Thanks Again. Keep writing. rapid testing houston
ReplyDelete