Types of Covid-19 Tests  

Types of Covid-19 Tests  

Covid-19 and Its Early Detection  

 

The Sars Cov 2 virus initially started the Covid-19 pandemic, which was then reported to cause at least 211,000 deaths worldwide by April 2020. It affected billions worldwide by increasing the morbidity and  mortality rates and shook the economy as a lot lost their jobs and livelihoods. Even since the numbers  started rising, a majority of laboratories, universities, and professional health experts have been looking  for efficient ways to detect the virus to prevent its further spread. (1

Those who are infected with the virus do not always present with symptoms, and those presenting  symptoms do not present with characteristic clinical manifestations. The variations of the signs and  symptoms of the Covid-19 virus are what make its detection difficult, especially at its early stages – since  this is when the symptoms are found to vary the most. This is why it is imperative that different forms of  Covid diagnostic tests are planned and introduced, which may not only allow an efficient diagnosis at  the clinic but at the comfort of the test taker’s home as well. 

 

Currently, two main types of Covid tests are available: the Molecular Assay Based Covid-19 Test and  Serological and Immunological Assays. 

 

Molecular Assay Based Covid-19 Test  

Molecular Assay Based Covid-19 Test

 

Reverse transcription-polymerase Chain Reaction  

 

The Reverse Transcriptase Polymerase Chain Reaction is considered a gold standard for the diagnosis of  the SARS-Cov-2 virus. It works by multiplying the small quantities of the viral genome which may be  taken from the person being tested. The samples for this particular test are recommended to be taken  from the upper respiratory tract by using the swab method. However, some may even take a sample  from the individual’s stool, serum, or secretions of the eye. (2) Some new technologies have also  allowed the use of saliva secretions instead of the more traditional sampling methods mentioned above.  These are not only proven way less painful for the individual being tested but are also much quicker. (3) The Reverse Transcriptase Polymerase Chain Reaction can be conducted as either a one-step or a two step procedure.  

One Step: This is also referred to as the real-time reverse transcription-polymerase chain  reaction. It requires only one tube which contains the necessary primers to allow the  conductance of the reaction. Since this is much quicker, it is now considered the preferred  approach by many. 

Two-Step: Since it is a two-step reaction, it uses more than one tube where the reverse  transcriptase and amplification reaction are conducted separately. The benefit of the two-step  procedure over the one-step procedure is that it is much more sensitive to slight changes and  offers higher flexibility. Moreover, unlike the one-step procedure, this also uses much less  starting material and allows the quantification of multiple targets. (4) 

 

Isothermal Nucleic Acid Amplification  

 

The Isothermal Nucleic Acid Amplification test allows the application of viral RNA at a constant  temperature, unlike the Reverse Transcription Polymerase Chain Reaction, which works on multiple  temperature variations and specifically designed thermal equipment. The Isothermal Nucleic Acid  Amplification systems include the Reverse Transcription Loop-Mediated Isothermal Amplification,  Transcription Mediated Amplification, CRISPR Based Analysis, Rolling Circle Amplification, Nucleic Acid  Hybridization using Microarray and Amplicon Based Metagenomic sequencing. (5

 

Reverse Transcription Loop-Mediated Isothermal Amplification  

The Reverse Transcription Loop-Mediated Isothermal Amplification allows the relatively cost effective and quick diagnostic testing of the SARS Cov-2 Virus. This system works by detecting

the viral RNA in the sample by enabling the combination of Loop-Mediated Isothermal  Amplification with the Reverse Transcription Reaction. The amplified product can then be seen through turbidity measurements, photometry and it may also be detected using intercalated  dye fluorescence in real-time. (6

 

Transcription-Mediated Amplification  

The transcription-mediated. The amplification procedure allows much more efficient detection  of certain parts of the viral genome as compared to the traditional Reverse Transcription Polymerase Chain Reaction. This is because this technology enables the rapid amplification of  the virus, which allows its easier detection. (7) 

CRISPR-Based Assays  

CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats, and it belongs to a  family of sequences of nucleic acids found in bacteria and other prokaryotic organisms. The  CRISPR-based assays work by recognizing these nucleic acid sequences and cut them using certain enzymes known as Cas9, Cas12, and Cas13 – more commonly called the CRISPR associated enzymes. (8

 

Rolling Circle Amplification  

The Rolling Circle Amplification is one of the more popularly known viral detection methods as it  allows the amplification of up to 109-fold in each 90 minutes cycle in isothermal conditions.  Unlike the false positive tests, which may be occasionally encountered with other tests like PCR based assays, the Rolling Circle Amplification tests are much more accurate. They also require a  minimum concentration of reagents to work. Even though this is hypothesized to be an effective  diagnostic system for the Covid-19 virus, it has not yet been introduced into the market for this  purpose.(9

Nucleic Acid Hybridization Using Microarray  

 

The Nucleic Acid Hybridisation using Microarray tests allows the quick detection of the Covid-19 virus,  which has to lead them to gain popularity over the past few years. These tests work by producing cDNA  from the RNA of the virus by using a reverse transcription procedure. They also facilitate the labeling of  the produced cDNA with precise probes, which are then loaded to microarray trays. (10) What makes  these tests different is their ability to detect the mutations in the viral genome and allow the accurate  detection of as much as 24 single nucleotide polymorphisms which are caused by the mutations.(11

Amplicon-Based Metagenomic Sequencing  

 

The Amplicon Based Metagenomic Sequencing uses two different approaches for the detection of the  viral genome like Covid-19 virus including:  

Amplicon Based Sequencing: This facilitates molecular epidemiology, contact tracing, and  conducting studies of the evolution of the virus. 

Metagenomic Sequencing: This allows the detection and evaluation of the infecting microbiome and its background. 

The dual approach of the viral detection offered by this system allows accurate assessment of the  infecting virus, its rate of mutation, and its ability to combine with other coronaviruses, infecting  humans.

Serological and Immunological Covid-19 Test  

Serological and Immunological Covid-19 Test

 

Serological tests are conducted by analyzing the blood plasma and serum of the individual being tested.  However, contrary to previous times, these tests may also be conducted using a wider range of samples, including sputum, saliva, and other body fluids, according to the patient’s preferences and the doctor’s  

expertise. The tests detect the presence of the two types of antibodies that may be produced in  response to a viral antigen in the body called IgM and IgG. The detection of these antibodies also opens the possibility for these tests to be used for vaccine development and evaluate the antibody response of  the body for the Covid-19 virus in the short term and long term. The method by which these may be  detected includes the Enzyme-Linked Immunosorbent Assay, Neutralization Bioassay,  Immunochromatographic Lateral Flow Assay, and certain chemosensors.  

Enzyme-Linked Immunosorbent Assay  

 

Enzyme-Linked Immunosorbent Assay, which is also commonly known as ELISA, is a plate-based assay  technique that allows the detection and quantification of different hormones, antibodies, proteins, and  peptides. It can also be quantitative and qualitative in nature, depending on the requirement. The test  usually takes between 1 and 5 hours to show results.  

Healgen Covid-19 Rapid Antibody Test Kit  

healgen antigen test kit

The Healgen Covid-19 Rapid Antibody Test Kits work by detecting the presence of IgG and IgM  antibodies in the blood, serum, and plasma of the individual. These antibodies may be seen after at least 1 to 3 weeks after the individual has been infected.

What makes the Healgen Covid-19 Rapid Antibody Test Kit particularly special is its ability to deliver  tests within 15 minutes. 

The kit is available as a box of 25 tests, at a price of £99.99. Moreover, the company offers a discount of  10% to those who purchase at least 4 to 9 kits, 15% to those who buy 10 to 20 kits, and a discount of  20% is offered to those who purchase more than 21 kits.  

Lateral Flow Immunoassay  

 

The Lateral Flow Immunoassay is a qualitative test that lets individuals know if they are positive or  negative for the Covid-19 virus. It is small and portable, which allows this test to be conducted outside  the healthcare setup as well. The results from the Lateral Flow immunoassay can be obtained within 10  to 30 minutes of the test. The test works by being exposed to a fluid sample, which then flows through  an immobilized viral antigen band within the test kit. If the individual is positive for the Covid-19 virus,  the antibodies for the virus accumulate on the band and leads to the development of an indicator color.  What makes this type of testing system particularly popular is its cost-effectiveness and the lack of  training requirements.  

Healgen Covid-19 Lateral Flow Rapid Antigen Test Kits  

The Healgen Covid-19 Lateral Flow Rapid Antigen Test Kits are qualitative tests that allow rapid testing  for Covid-19 at a price of £6.49 per test kit. On purchase of 4 to 9 kits, a discount of 10% is offered, while  a 15% discount is offered for every 10 to 20 test kits purchased. However, on purchasing more than 21  test kits, the site also offers a discount of 20%.  

Neutralization Assay  

 

The Neutralisation Assays work by detecting and determining the ability of the antibodies produced by  the body to inhibit the spread of the virus in the cultured cells and its effects. It usually requires a whole  blood sample of the individual; however, it may also be conducted using their serum or plasma. These  samples are then diluted and introduced to cell cultures. It takes almost 3 to 5 days for the test results  to come; however, certain recent advances within the Neutralization assay tests have reduced this time  from day to hours. (12

Luminescent Immunoassay  

 

The Luminescent Immunoassay involves chemiluminescence and fluorescence, which work by lowering the antibody detection limits by the specific reagents.  

Biosensor Test  

The Biosensor tests work by conversion of specific biomolecules into measurable readout. IT usually  achieves this through different methods like optics, electricity, and enzymes. 

Rapid Antigen Test  

The Rapid Antigen allows the detection of viral antigens in the samples taken from a potentially infected  individual. The Antigen detection is facilitated by specific monoclonal antibodies, which allow an analysis  of the sample. (13)  

 

Home Test Kits  

The Home Test Kits by Hughes Healthcare work on the mechanism of Rapid Antigen Testing and provide  an affordable solution for at-home testing for the Covid-19 virus. The test kits are available at a price of 

£13.99 per test kit. The site offers a further discount of 10% for anyone who purchases 4 to 9 kits, 15%  for those who purchase 10 to 20 kits, and a 20% discount for those who buy more than 21 kits. 

What makes Hughes Healthcare’s Coronavirus antigen rapid test popular is its ease of use and quick  results. Moreover, the test is proved to be 96.8% sensitive and 97.1% specific, which leads to slim chances of any false positives or false negatives, which are commonly seen with other testing systems. (14) 

 

Commonly Asked Questions Regarding Covid-19 Tests   

Commonly Asked Questions Regarding Covid-19 Tests

Can Anyone in the House use the at-home Covid-19 Test Kits I Ordered? 

Since the covid-19 tests kits that may be ordered at home are not specific to a particular individual and are activated only after the exposure to the sample retrieved from the individual.  However, one test kit should only be consumed by one individual and cannot be reused.  

How Often should the Covid-19 Tests be Taken Without Symptoms? 

If you have no symptoms for the covid-19 virus and have not been in any recent contact with a  possibly infected individual, there is no need for a Covid-19 test. However, there are certain  situations where tests may need to be conducted even in a symptomless state which include  traveling by plane, visiting an old or sick individual, or if you believe you have been in prolonged  contact with an infected individual. 

What Does a Negative Antibody Test Indicate?

A negative antibody test indicates the absence of antibodies for the covid 19 virus in the body.  This means either the test was conducted too early and the antibodies have not yet developed  in the body, or the person has not been infected with the virus. 

 

Does the presence of Covid-19 antibodies mean the person is immune? 

Studies are still being conducted to understand the full extent of the immunity caused by the  presence of antibodies in the system. The presence of antibodies usually indicates that the  person was infected by the virus in the past, or it may also indicate a current infection.

Conclusion  

When looking for the ideal diagnostic test for the detection of Covid-19, it is essential to keep in mind  that each test type is unique and has its own sensitivity and specificity ratios. While some tests may be  more accurate and take time to deliver results, the others test may allow a much quicker outcome. Still, the test has variable accuracy – hence it is up to the individual and their healthcare professional to  choose a test accordingly. Moreover, since it is possible to occasionally have a false negative or a false  positive with the Codi-19 tests as well, one should also consult a healthcare professional to look over  their clinical and epidemiological history.  

References: 

  1. Carter LJ, Garner LV, Smoot JW, Li Y, Zhou Q, Saveson CJ, Sasso JM, Gregg AC, Soares DJ, Beskid  TR, Jervey SR, Liu C. Assay Techniques and Test Development for COVID-19 Diagnosis. ACS Cent  Sci. 2020 May 27;6(5):591-605. doi: 10.1021/acscentsci.0c00501. Epub 2020 Apr 30. PMID:  32382657; PMCID: PMC7197457. 
  2. Xia J, Tong J, Liu M, Shen Y, Guo D. Evaluation of coronavirus in tears and conjunctival secretions  of patients with SARS-CoV-2 infection. J Med Virol. 2020 Jun;92(6):589-594. doi:  10.1002/jmv.25725. Epub 2020 Mar 12. PMID: 32100876; PMCID: PMC7228294. 
  3. Rutgers University; New Rutgers Saliva Test for Coronavirus Gets FDA Approval: Emergency Use  Authorization Granted for New Biomaterial Collection Approach. Rutgers Today, April 2020. 4. Wong ML, Medrano JF. Real-time PCR for mRNA quantitation. Biotechniques. 2005 Jul;39(1):75- 85. doi: 10.2144/05391RV01. PMID: 16060372. 
  4. Notomi T, Okayama H, Masubuchi H, Yonekawa T, Watanabe K, Amino N, Hase T. Loop mediated isothermal amplification of DNA. Nucleic Acids Res. 2000 Jun 15;28(12):E63. doi:  10.1093/nar/28.12.e63. PMID: 10871386; PMCID: PMC102748. 
  5. Hong TC, Mai QL, Cuong DV, Parida M, Minekawa H, Notomi T, Hasebe F, Morita K.  Development and evaluation of a novel loop-mediated isothermal amplification method for  rapid detection of severe acute respiratory syndrome coronavirus. J Clin Microbiol. 2004  May;42(5):1956-61. doi: 10.1128/JCM.42.5.1956-1961.2004. PMID: 15131154; PMCID:  PMC404656. 
  6. Kacian D. L.; Fultz T. J. Kits for nucleic acid sequence amplification methods. U.S. Patent  4888779, 1999. patft.uspto.gov/netacgi/nph 
  7. What is CRISPR? Ask the Brain, January 1, 2019. The McGovern Institute for Brain Research,  Massachusetts Institute of Technology. mcgovern.mit.edu/2019/01/01/crispr-in-a-nutshell/. 9. Wang B, Potter SJ, Lin Y, Cunningham AL, Dwyer DE, Su Y, Ma X, Hou Y, Saksena NK. Rapid and  sensitive detection of severe acute respiratory syndrome coronavirus by rolling circle 
  8. Chen Q, Li J, Deng Z, Xiong W, Wang Q, Hu YQ. Comprehensive detection and identification of  seven animal coronaviruses and human respiratory coronavirus 229E with a microarray  hybridization assay. Intervirology. 2010;53(2):95-104. doi: 10.1159/000264199. Epub 2009 Dec  3. PMID: 19955814; PMCID: PMC7179550. 
  9. Guo X, Geng P, Wang Q, Cao B, Liu B. Development of a single nucleotide polymorphism DNA  microarray for the detection and genotyping of the SARS coronavirus. J Microbiol Biotechnol.  2014 Oct;24(10):1445-54. doi: 10.4014/jmb.1404.04024. PMID: 24950883. 
  10. Postnikova EN, Pettitt J, Van Ryn CJ, Holbrook MR, Bollinger L, Yú S, Caì Y, Liang J, Sneller MC,  Jahrling PB, Hensley LE, Kuhn JH, Fallah MP, Bennett RS, Reilly C. Scalable, semi-automated  fluorescence reduction neutralization assay for qualitative assessment of Ebola virus neutralizing antibodies in human clinical samples. PLoS One. 2019 Aug 27;14(8):e0221407. doi:  10.1371/journal.pone.0221407. PMID: 31454374; PMCID: PMC6711594. 
  11. Diagnosis of acute respiratory syndrome coronavirus 2 infection by detection of nucleocapsid  protein. medRxiv 2020, 2020.03.07.20032524.10.1101/2020.03.07.20032524. 14. Procop GW, Kadkhoda K, Rhoads DD, Gordon SG, Reddy AJ. Home testing for COVID-19: Benefits  and limitations. Cleve Clin J Med. 2021 Mar 1. doi: 10.3949/ccjm.88a.ccc071. Epub ahead of  print. PMID: 33579779.

 

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