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COVID-19 Test


COVID-19 TEST


You will provide

Nasopharyngeal swab and/or a Throat swab (Molecular Test)

Blood Sample (Antibody test)

This test is for both

Male, Female

Test Preparation

No preparation required


OVERVIEW


What is Corona Virus Identification?

Coronavirus (SARS-CoV-2) is a new (novel) virus that first showed up in December 2019 and spread all through the globe at an alarming rate, prompting the World Health Organization to declare the outbreak a pandemic and the Nigerian ministry of Health to declare a public health emergency. As the pandemic continues, scientists continue to study the virus and gain more knowledge about COVID-19 disease.

As indicated by its names, SARS-CoV-2 shares genetics similarities to the original SARS-CoV that appeared in 2003. However, even though the two are strains of the same viral species, the novel coronavirus made the jump to humans separately and is not actually a direct descendant of the one that caused the first coronavirus epidemic two decades ago. Even so, the symptoms of the diseases these two viruses cause are fairly similar.

It takes between two to 14 days after being exposed to SARS-CoV-2 to develop the COVID-19 disease. The symptoms range from mild to severe and most commonly include fever – i.e, temperatures above 100.4°F (38°C) - dry cough and shortness of breath. Runny nose, sneezing and sore throat can sometimes occur, as can fatigue and muscle pain. Diarrhea, nausea and headaches are less common symptoms. In more serious cases, COVID-19 can progress to pneumonia, multiple organ failure – and even death.

The bad news is that we still don’t know how contagious people are during the symptomless, incubation period. And even though not really common, asymptomatic cases have also been reported. This means that there may be many young people who don’t know they are sick with COVID-19 passing on the virus to people who belong in the most vulnerable categories; older adults and people suffering from chronic conditions such as diabetes, lung or heart diseases. Early estimates say that the fatality rate for this subset of people might be several times higher than the average death rate for the disease, which varies from country to country, and is reported to be anywhere between 1.4% and 3.5%.

There is no way to know if you are infected with COVID-19 unless you get tested. Only medical professionals can do the specialized test on respiratory samples that, in turn are usually obtained from the back of the nose or the throat of the suspected patient. In most countries, the results are available within few hours.

As in the case with all Coronaviruses, there is currently neither treatment nor vaccine for COVID-19. Symptoms, in most people will usually go away on their own. Getting plenty of rest and drinking fluids should help. However, you should seek immediate medical help if you are in the vulnerable categories and if you experience breathing problems. It is even more important to do whatever is in your power not to pass on the virus to others. So, stay at home.

Many diagnostic tests for coronavirus disease 2019 (COVID-19) are available so far, with more gaining emergency approval daily. These tests are mostly based on four different techniques:

1) Reverse transcription polymerase chain reaction (RT-PCR) – the present standard test for COVID-19,

2) Loop-mediated isothermal amplification (LAMP) – a simple, but less advanced testing method

3) Lateral flow – hand-held single-use assays providing results for an individual patient in as lilltl as 15 minutes

4) Enzyme-linked immunosorbent assay (ELISA) – quick and technically simple tests that are easily read and offer relatively high throughput. 


Reverse-Transcription Polymerase Chain Reaction (RT-PCR)


Technology overview

PCR is a very common scientific method that has been generally used in research and medicine for about 20-30 years to detect genetic information. RT-PCR is a unique version used when RNA is being detected and it is now being used as a test to detect SARS-CoV-2, the virus causing COVID-19. This type of test has normally been used as a frontline test for COVID-19 as it directly tests for the presence of the virus RNA.

RT-PCR tests are quick, sensitive and reliable, capable of producing results in 3-4 hours, although this usually takes longer if samples must first be sent to specialized external laboratories (6-8 hours on average).

Many diagnostic and research companies produce RT-PCR products, tests and machines so the technology is usually available. Some RT-PCR tests are developed as an `all in one’ kit, decreasing laboratory handling and potential for contamination.

How it works

When a sample has been collected, chemicals are used to remove any proteins, fats and other molecules, leaving only RNA. This will be a mixture of a person’s genetic material along with any viral RNA that might be present.

The test kit enzymes copy the RNA to DNA, which is amplified to enable virus detection by using a PCR machine which cycles the test temperature so that approximately 35 billion copies of viral DNA are made for each viral RNA strand that was initially present.

Fluorescent markers are normally used to bind to the amplified DNA and produce light, which can be read by the machine to produce the test result. If the intensity of the light produced within the sample gets to a certain threshold, this is classified as a positive test. The number of PCR temperature cycles that were needed before the fluorescence threshold was reached is recorded and gives an estimate of how much virus was present in the patient sample.

What does the test detect?
RT-PCR detects if viral RNA is present in samples from a patient or not. This is done by capturing and amplifying regions of the virus’ genetic material, usually the Spike protein, N protein or Envelope.
To measure the viral RNA, it is changed to DNA, copied many times using repeated temperature cycles in a PCR machine and then fluorescent markers are used to detect the virus. If the amount of fluorescence goes above a specific level, this proves that the virus is present. The number of temperature cycles the machine does to reach this threshold is recorded to estimate how much virus was present in the patient sample. The lower the number of cycles, the more virus that was present. Usually, these samples are taken from the nose or throat using either long or short swabs, but samples can be collected in other ways too. Taking samples from where the virus is shedding or multiplying, improves the accuracy of the test.

What does the result mean?
An RT-PCR test is very sensitive and fairly reliable if done on a sample from an infected part of the body whilst an active infection is occurring.

Positive test result: – A positive PCR result means that the person the sample was taken from is presently infected by the virus.
Negative test result: – A negative PCR result could mean that the person is not presently infected by this virus, the virus is not existent at the site the sample was taken from, the sample taken was of poor quality, or that it is too early or too late in the infection to detect duplicating virus. This is why negative test results need new patient samples to be taken a few days later to reduce the chance of mistakenly missing an infected person.

The RT-PCR test cannot detect if a person had the virus before and then cleared it after the end of the COVID-19 disease, i.e. if a person had the disease, as it only detects when active virus is present.

Advantages and limitations
Advantages:

  • RT-PCR is accepted by scientists and medical staff as a strong and well documented technique.
  • With RT-PCR being so widely known in research and medicine, the technology is already in place to test for COVID-19.
  • RT-PCR can detect current infections of disease, allowing medical staff to know who is presently infected and who is not.

Disadvantages:

  • RT-PCR depends on capturing and detecting the virus and so it is possible to miss patients who have cleared virus and recovered from disease.
  • The circulation of virus across the respiratory tract differs between patients, so even if a person is infected, the virus may only be detectable in sputum or nasopharyngeal swab but not necessarily at both locations at the same time.
  • RT-PCR for COVID-19 can only tell if a person is presently infected with this particular coronavirus. It can’t give information on other diseases or symptoms.

Loop-Mediated Isothermal Amplification (LAMP)


Technology overview
Loop-mediated Isothermal Amplification (LAMP) is a similar procedure to RT-PCR, but instead of using a series of temperature changes to produce replicas of the viral DNA, LAMP is conducted at a constant temperature of 60-65°C.
The amount of DNA produced in LAMP is much higher than in RT-PCR and a positive test result can be seen visually without needing a machine to read the results.
LAMP is a newer technique compared to RT-PCR, but it is simple and easy for a trained scientist to do, making it a potentially useful technique for detection of COVID-19. As it is a newer technology, there is less evidence on its use, but diagnostic companies are currently carrying out clinical trials to support it.

How it works
LAMP assays for COVID-19 begins with the collection of samples from the nose or throat using a swab, but can also use samples gotten using other methods too such as mucus produced from hard coughing.
Like RT-PCR, the viral RNA in the sample is changed to DNA which allows it to be copied.
The amplification of the viral DNA using LAMP technology and reagents can be detected when the reaction mixture is turned cloudy as a result of the production of a chemical called ‘magnesium pyrophosphate’. As this cloudiness can be seen by the naked eye, it allows easy diagnosis of COVID-19 by scientists.
The accuracy of the results can be enhanced by making use of special fluorescent dyes or colour-changing dyes in the reaction mixture.
As the dyes interact with the viral DNA, the intensity of the light or colour change can be measured to give the estimated number of viral RNA molecules that were originally in the sample.

What does the test detect?
Like RT-PCR, LAMP detects if viral RNA is present in samples from a patient or not. This is done by capturing and amplifying regions of the virus’ genetic material, usually the Spike protein, N protein, Envelope or multiple regions at once.
Samples can be collected in the same way as they are for RT-PCR, normally from the nose or throat using long or short swabs, or through mucus produced when a person coughs. In order to measure the viral RNA, it must be changed to DNA using an enzyme and copied many times. The results of the test are gotten based on the cloudiness or colour change of the reaction mixture.

What does the result mean?

Like RT-PCR, LAMP tests are very sensitive and reliable if done on a sample from an infected part of the body whilst an active infection is occurring.

Positive test result: – A positive LAMP result means that the person the sample was taken from is presently infected by the virus.
Negative test result: – A negative LAMP result could mean that the person is not presently infected by this virus, the virus is not existent at the site the sample was taken from, or that it is too early or too late in the infection to detect duplicating virus. This is why when test results are negative, new patient samples are taken a few days later to reduce the chance of mistakenly missing an infected person.

LAMP tests cannot detect if a person had the virus before and then cleared it after the end of the COVID-19 disease, i.e. if a person had the disease or not, as it only detects when active virus is present.

Advantages and limitations

Advantages:                                  

  • LAMP is a fast technique that can produce results in 2-3 hours.
  • Results can be read by eye.
  • The simple and inexpensive method can be done within hospital laboratories, improving the time between collecting a sample and getting a diagnosis.
  • LAMP can detect current infections of disease, allowing medical staff to know who is presently infected and who is not.

Disadvantages:

  • The technology is newer than RT-PCR and does not have a large background of research behind it. Tests using LAMP technology for COVID-19 are still being evaluated in clinical settings.
  • The science behind building these tests is harder than RT-PCR.
  • LAMP tests depend on on capturing and detecting the virus and so it is possible to miss patients who have cleared virus and recovered from disease.
  • The circulation of virus differs across the respiratory tract between patients, so even if a person is infected the virus may only be detectable in sputum or nasopharyngeal swab but not necessarily at both locations at the same time.
  • LAMP tests for COVID-19 can only tell if a person is presently infected with this particular coronavirus. It can’t provide information on other diseases or symptoms and does not tell staff if a patient has been infected before with the virus or if a patient has any immunity to the virus.

Lateral Flow / Colloidal Gold Immunochromatography 


Technology overview
Lateral flow assays have normally been referred to as ‘Antibody tests’ in the media as they are presently used to detect antibodies to disease in a patient’s blood. The technology is also being assessed for antigen use.
Lateral flow assays use the same technology normally used for pregnancy tests. Lateral flow tests can detect antibody to virus from patient blood specifying that the patient has COVID-19 or has recovered from COVID-19. Rarely, lateral flow tests can be used to detect the presence of active virus by detecting virus proteins directly.

Antibody lateral flow tests for SARS-CoV-2 are produced as test kits used by a specialist rather than by patients themselves. They need a drop of patient blood, either from a vein or from a small finger prick, similar to a finger prick test used for blood sugar monitoring in some types of diabetes.
These types of tests work very differently to RT-PCR and LAMP techniques and detect the patient’s immune antibody response to the virus instead of detecting the virus itself.
Lateral flow antibody tests can be done rapidly and the tests can be produced cheaply, so various diagnostics companies are working hard to develop lateral flow tests for SARS-CoV-2.
A major advantage for this type of test is also the ability to see if patients are presently infected or have recovered from COVID-19 even if they have fully recovered and cleared the virus months ago. However, it cannot differentiate between an active and a previous infection.

How it works
Lateral flow immunoassays for COVID-19 are simple tools that can detect antibodies in the blood.
A small sample of patient blood is gotten from a vein or from a finger-prick by a scientist and dropped onto a spongy pad within the test device. A few drops of a diluting liquid called a ‘buffer’ are added to help the blood sample flow across the device.
As the sample moves through the device, antibodies against SARS-CoV-2 that are existent in the sample will attach to chemicals in the device, capturing the antibodies on the test and control lines. This capturing and binding process leads to a colour change along the test and control lines which can be seen by eye, producing one, two or three lines depending on the type of antibodies that are present(IgM or IgG).

What does the test detect?

Lateral flow immunoassays for SARS-CoV-2 detect two types of protective antibodies that are produced by the body when the immune system identifies a foreign structure, in this case SARS-CoV-2, the virus causing COVID-19.
These antibodies help fight the disease and stay in the blood for months after the virus and disease is cleared. The presence of antibodies in the body is usually referred to as immunity or that a person is immune to a virus, as these antibodies protect against re-infection and return of the same disease.
When we are infected by virus, our immune system generates early `prototype’ antibodies (IgM) with intermediate strength binding to virus, that are able to start working to clear virus about 5 days after a new infection. Usually, at 8 to 10 days after infection, IgG antibodies with high binding strength, can work to help more rapid virus clearance. Antibodies act by generating a matching contoured surface to stick to foreign antigens, using a refined selection process to amplify antibodies with the best surface match and strongest binding.

Antibody lateral flow immunoassays can be made to detect IgM or IgG alone or both together.

Antigen lateral flow immunoassays are an even newer technology with extra scientific and technical challenges which means they are not likely to be developed during the pandemic period. These antigen assays detect the virus directly without the amplification steps of RT-PCR and LAMP, and like those tests are only able to detect existing active viral infection but not past infection.

What does the result mean?
Antibody lateral flow immunoassays identify antibodies to the virus in the blood. They don’t detect the virus itself. The ability to detect the immune system response dependably using only one sample (blood) is a big advantage, as is the amplification of the detection signal generated by the body immune response. Using the antibody response alone does not allow distinction between individuals who are presently infected and those who have cleared the virus infection.
Antibody tests provide a huge important ability to detect past infection with virus to identify people who were asymptomatic, people who have cleared the virus and so no longer risk being infected or spreading the virus to others. In addition, antibody tests are important for assessing population spread of the virus and the level of ‘herd’ immunity in the population. This is essential for understanding the potential consequences of lifting or enforcing measures to control the virus such as quarantine, social distancing, school and workplace closures.
The antibody IgG and IgM lateral flow immunoassay tests are not difficult to read:
A control line must appear to show that the assay has worked properly.
Then, test lines will show if either of the antibody types are found in the sample. The presence of lines for IgG or IgM, or both indicate a positive test – indicating that the patient has been infected with the COVID-19 coronavirus.

Advantages and limitations

Advantages:

  • Lateral flow assays are very quick per patient, giving results in just 15 minutes.
  • Testing levels of antibody in blood permits a single patient sample from one accessible part of the body where sampling is non-invasive to be tested for presence of virus.
  • These tests need very little training to perform and don’t rely on specialist laboratories or scientists to analyze.

Disadvantages:

  • The technology is new and the evidence for its accuracy in coronavirus diagnosis is still being assessed.
  • Thus far, available lateral flow tests can only determine if a patient has at some point been infected with COVID-19. Further testing would be required to check if a patient is presently infected. Future versions of this technology might allow scientists to detect current infections.
  • Lateral flow tests are more expensive and takes a lot of time for large batch testing than specialist laboratory based antibody tests such as ELISA.

Enzyme-Linked Immunosorbent Assay (ELISA)


Technology overview
An Enzyme-Linked Immunosorbent Assay (ELISA) is a common biochemical method that can be used to detect antigens or antibodies, depending on the type of test used.
ELISAs use enzymes linked to antibodies that can attach to the molecule that is being tested for and cause a colour change that can be measured by a specialized machine. The strength of the colour change gives scientists an idea of the number of molecules of interest in the sample.
ELISAs can be done as standard batches of up to 96 assays completed at the same time, allowing cheap and time effective method for batch testing of large numbers of patient samples at the same time. This technology could help accelerate the number of patients that can be tested for SARS-CoV-2. The most effective ELISA assays in checking prior infection detect antibodies against SARS-CoV-2. Future ELISA could be used to test for active virus infection by detection of virus protein (antigen) testing, but this testing will not be as accurate and is not proven yet.

How it works
An ELISA detects antibodies formed in patient blood as a result infection with SARS-CoV-2. The entire test can be done in one tube or well and involves mixing patient samples, antibodies, antigens and enzymes together with a colour changing molecule. 

What does the test detect?
ELISA tests to detect antibodies are detecting the antibody reaction to COVID-19 infection.
Detecting antibodies to SARS-CoV-2 could tell a scientist if a patient has been infected with COVID-19, either presently or in the past. However, infected patients will not be noticed immediately on infection, but only when the immune system to the virus can be discovered in blood, approximately 5 days after infection for a test detecting IgM antibodies, which is about the exact time that symptoms/signs occur. Present facts propose once a person has been infected with virus, their immune system will avert a future infection with the same virus.
This antibody ELISA test provides very essential information for diagnosis, management and recovery from COVID-19 and will also help researchers evaluate how many people in the population have been infected, which is vital for planning infection control.

What does the result mean?
An antibody test using ELISA would display a positive result if the patient has antibodies to COVID-19. This might not mean that they presently have the virus, only that they have had it at some point. This is because antibodies stay in the blood even after the infection is gone to help provide the body with immunity if they come into contact with the virus again.
A negative result would mean that the patient has not been infected with COVID-19 and may have no resistance against it.

ELISA antigen tests may be developed in the future to detect existing infections. Such an antigen test using ELISA would display a positive result (colour change) if a patient has COVID-19 in their blood. This would show that the patient is currently infected with the COVID-19. A negative result (no colour change) would show that no COVID-19 antigens were found in the patient’s sample. This could mean that the patient does not have COVID-19. It might also mean that they are too early in their infection to be positive. If they have symptoms of COVID-19 they should be tested again a few days later to be sure.

Advantages and limitations

Advantages:

  • ELISA is a simple and inexpensive laboratory technique.
  • ELISA is well-known and documented within science and medicine.
  • Results can usually be produced within 1 to 3 hours of taking a patient sample.
  • Because it is so quick to carry out, it can be done in a hospital laboratory, reducing the time to diagnosis.
  • ELISA testing can be done on multiple samples at once, so it can be used for rapid testing scaled up to test larger numbers of patients.

Disadvantages:

  • ELISA tests are not yet well established for SARS-CoV-2 COVID-19 testing, although several companies are working hard to produce them and test them in patients.

CONCLUSIONS

  • Four main types of tests are being used or developed to test for SARS-CoV-2, the virus causing COVID-19.
  • These tests are at different stages of development, authentication and production.
  • Each test type has its own different advantages and disadvantages inherent to the underlying technology.
  • A mixture of testing types used at different times may be valuable for patient management and population pandemic control of COVID-19.


DisclaimerThe information provided herein is for patient general knowledge only and should not be used during any medical emergency, for the diagnosis or treatment of any medical condition. Duplication for personal and commercial use must be authorized in writing by Surjen.com.


COVID-19 Test
N 39500
COVID-19 Test COVID-19 Test

View Description


COVID-19 TEST


You will provide

Nasopharyngeal swab and/or a Throat swab (Molecular Test)

Blood Sample (Antibody test)

This test is for both

Male, Female

Test Preparation

No preparation required


OVERVIEW


What is Corona Virus Identification?

Coronavirus (SARS-CoV-2) is a new (novel) virus that first showed up in December 2019 and spread all through the globe at an alarming rate, prompting the World Health Organization to declare the outbreak a pandemic and the Nigerian ministry of Health to declare a public health emergency. As the pandemic continues, scientists continue to study the virus and gain more knowledge about COVID-19 disease.

As indicated by its names, SARS-CoV-2 shares genetics similarities to the original SARS-CoV that appeared in 2003. However, even though the two are strains of the same viral species, the novel coronavirus made the jump to humans separately and is not actually a direct descendant of the one that caused the first coronavirus epidemic two decades ago. Even so, the symptoms of the diseases these two viruses cause are fairly similar.

It takes between two to 14 days after being exposed to SARS-CoV-2 to develop the COVID-19 disease. The symptoms range from mild to severe and most commonly include fever – i.e, temperatures above 100.4°F (38°C) - dry cough and shortness of breath. Runny nose, sneezing and sore throat can sometimes occur, as can fatigue and muscle pain. Diarrhea, nausea and headaches are less common symptoms. In more serious cases, COVID-19 can progress to pneumonia, multiple organ failure – and even death.

The bad news is that we still don’t know how contagious people are during the symptomless, incubation period. And even though not really common, asymptomatic cases have also been reported. This means that there may be many young people who don’t know they are sick with COVID-19 passing on the virus to people who belong in the most vulnerable categories; older adults and people suffering from chronic conditions such as diabetes, lung or heart diseases. Early estimates say that the fatality rate for this subset of people might be several times higher than the average death rate for the disease, which varies from country to country, and is reported to be anywhere between 1.4% and 3.5%.

There is no way to know if you are infected with COVID-19 unless you get tested. Only medical professionals can do the specialized test on respiratory samples that, in turn are usually obtained from the back of the nose or the throat of the suspected patient. In most countries, the results are available within few hours.

As in the case with all Coronaviruses, there is currently neither treatment nor vaccine for COVID-19. Symptoms, in most people will usually go away on their own. Getting plenty of rest and drinking fluids should help. However, you should seek immediate medical help if you are in the vulnerable categories and if you experience breathing problems. It is even more important to do whatever is in your power not to pass on the virus to others. So, stay at home.

Many diagnostic tests for coronavirus disease 2019 (COVID-19) are available so far, with more gaining emergency approval daily. These tests are mostly based on four different techniques:

1) Reverse transcription polymerase chain reaction (RT-PCR) – the present standard test for COVID-19,

2) Loop-mediated isothermal amplification (LAMP) – a simple, but less advanced testing method

3) Lateral flow – hand-held single-use assays providing results for an individual patient in as lilltl as 15 minutes

4) Enzyme-linked immunosorbent assay (ELISA) – quick and technically simple tests that are easily read and offer relatively high throughput. 


Reverse-Transcription Polymerase Chain Reaction (RT-PCR)


Technology overview

PCR is a very common scientific method that has been generally used in research and medicine for about 20-30 years to detect genetic information. RT-PCR is a unique version used when RNA is being detected and it is now being used as a test to detect SARS-CoV-2, the virus causing COVID-19. This type of test has normally been used as a frontline test for COVID-19 as it directly tests for the presence of the virus RNA.

RT-PCR tests are quick, sensitive and reliable, capable of producing results in 3-4 hours, although this usually takes longer if samples must first be sent to specialized external laboratories (6-8 hours on average).

Many diagnostic and research companies produce RT-PCR products, tests and machines so the technology is usually available. Some RT-PCR tests are developed as an `all in one’ kit, decreasing laboratory handling and potential for contamination.

How it works

When a sample has been collected, chemicals are used to remove any proteins, fats and other molecules, leaving only RNA. This will be a mixture of a person’s genetic material along with any viral RNA that might be present.

The test kit enzymes copy the RNA to DNA, which is amplified to enable virus detection by using a PCR machine which cycles the test temperature so that approximately 35 billion copies of viral DNA are made for each viral RNA strand that was initially present.

Fluorescent markers are normally used to bind to the amplified DNA and produce light, which can be read by the machine to produce the test result. If the intensity of the light produced within the sample gets to a certain threshold, this is classified as a positive test. The number of PCR temperature cycles that were needed before the fluorescence threshold was reached is recorded and gives an estimate of how much virus was present in the patient sample.

What does the test detect?
RT-PCR detects if viral RNA is present in samples from a patient or not. This is done by capturing and amplifying regions of the virus’ genetic material, usually the Spike protein, N protein or Envelope.
To measure the viral RNA, it is changed to DNA, copied many times using repeated temperature cycles in a PCR machine and then fluorescent markers are used to detect the virus. If the amount of fluorescence goes above a specific level, this proves that the virus is present. The number of temperature cycles the machine does to reach this threshold is recorded to estimate how much virus was present in the patient sample. The lower the number of cycles, the more virus that was present. Usually, these samples are taken from the nose or throat using either long or short swabs, but samples can be collected in other ways too. Taking samples from where the virus is shedding or multiplying, improves the accuracy of the test.

What does the result mean?
An RT-PCR test is very sensitive and fairly reliable if done on a sample from an infected part of the body whilst an active infection is occurring.

Positive test result: – A positive PCR result means that the person the sample was taken from is presently infected by the virus.
Negative test result: – A negative PCR result could mean that the person is not presently infected by this virus, the virus is not existent at the site the sample was taken from, the sample taken was of poor quality, or that it is too early or too late in the infection to detect duplicating virus. This is why negative test results need new patient samples to be taken a few days later to reduce the chance of mistakenly missing an infected person.

The RT-PCR test cannot detect if a person had the virus before and then cleared it after the end of the COVID-19 disease, i.e. if a person had the disease, as it only detects when active virus is present.

Advantages and limitations
Advantages:

  • RT-PCR is accepted by scientists and medical staff as a strong and well documented technique.
  • With RT-PCR being so widely known in research and medicine, the technology is already in place to test for COVID-19.
  • RT-PCR can detect current infections of disease, allowing medical staff to know who is presently infected and who is not.

Disadvantages:

  • RT-PCR depends on capturing and detecting the virus and so it is possible to miss patients who have cleared virus and recovered from disease.
  • The circulation of virus across the respiratory tract differs between patients, so even if a person is infected, the virus may only be detectable in sputum or nasopharyngeal swab but not necessarily at both locations at the same time.
  • RT-PCR for COVID-19 can only tell if a person is presently infected with this particular coronavirus. It can’t give information on other diseases or symptoms.

Loop-Mediated Isothermal Amplification (LAMP)


Technology overview
Loop-mediated Isothermal Amplification (LAMP) is a similar procedure to RT-PCR, but instead of using a series of temperature changes to produce replicas of the viral DNA, LAMP is conducted at a constant temperature of 60-65°C.
The amount of DNA produced in LAMP is much higher than in RT-PCR and a positive test result can be seen visually without needing a machine to read the results.
LAMP is a newer technique compared to RT-PCR, but it is simple and easy for a trained scientist to do, making it a potentially useful technique for detection of COVID-19. As it is a newer technology, there is less evidence on its use, but diagnostic companies are currently carrying out clinical trials to support it.

How it works
LAMP assays for COVID-19 begins with the collection of samples from the nose or throat using a swab, but can also use samples gotten using other methods too such as mucus produced from hard coughing.
Like RT-PCR, the viral RNA in the sample is changed to DNA which allows it to be copied.
The amplification of the viral DNA using LAMP technology and reagents can be detected when the reaction mixture is turned cloudy as a result of the production of a chemical called ‘magnesium pyrophosphate’. As this cloudiness can be seen by the naked eye, it allows easy diagnosis of COVID-19 by scientists.
The accuracy of the results can be enhanced by making use of special fluorescent dyes or colour-changing dyes in the reaction mixture.
As the dyes interact with the viral DNA, the intensity of the light or colour change can be measured to give the estimated number of viral RNA molecules that were originally in the sample.

What does the test detect?
Like RT-PCR, LAMP detects if viral RNA is present in samples from a patient or not. This is done by capturing and amplifying regions of the virus’ genetic material, usually the Spike protein, N protein, Envelope or multiple regions at once.
Samples can be collected in the same way as they are for RT-PCR, normally from the nose or throat using long or short swabs, or through mucus produced when a person coughs. In order to measure the viral RNA, it must be changed to DNA using an enzyme and copied many times. The results of the test are gotten based on the cloudiness or colour change of the reaction mixture.

What does the result mean?

Like RT-PCR, LAMP tests are very sensitive and reliable if done on a sample from an infected part of the body whilst an active infection is occurring.

Positive test result: – A positive LAMP result means that the person the sample was taken from is presently infected by the virus.
Negative test result: – A negative LAMP result could mean that the person is not presently infected by this virus, the virus is not existent at the site the sample was taken from, or that it is too early or too late in the infection to detect duplicating virus. This is why when test results are negative, new patient samples are taken a few days later to reduce the chance of mistakenly missing an infected person.

LAMP tests cannot detect if a person had the virus before and then cleared it after the end of the COVID-19 disease, i.e. if a person had the disease or not, as it only detects when active virus is present.

Advantages and limitations

Advantages:                                  

  • LAMP is a fast technique that can produce results in 2-3 hours.
  • Results can be read by eye.
  • The simple and inexpensive method can be done within hospital laboratories, improving the time between collecting a sample and getting a diagnosis.
  • LAMP can detect current infections of disease, allowing medical staff to know who is presently infected and who is not.

Disadvantages:

  • The technology is newer than RT-PCR and does not have a large background of research behind it. Tests using LAMP technology for COVID-19 are still being evaluated in clinical settings.
  • The science behind building these tests is harder than RT-PCR.
  • LAMP tests depend on on capturing and detecting the virus and so it is possible to miss patients who have cleared virus and recovered from disease.
  • The circulation of virus differs across the respiratory tract between patients, so even if a person is infected the virus may only be detectable in sputum or nasopharyngeal swab but not necessarily at both locations at the same time.
  • LAMP tests for COVID-19 can only tell if a person is presently infected with this particular coronavirus. It can’t provide information on other diseases or symptoms and does not tell staff if a patient has been infected before with the virus or if a patient has any immunity to the virus.

Lateral Flow / Colloidal Gold Immunochromatography 


Technology overview
Lateral flow assays have normally been referred to as ‘Antibody tests’ in the media as they are presently used to detect antibodies to disease in a patient’s blood. The technology is also being assessed for antigen use.
Lateral flow assays use the same technology normally used for pregnancy tests. Lateral flow tests can detect antibody to virus from patient blood specifying that the patient has COVID-19 or has recovered from COVID-19. Rarely, lateral flow tests can be used to detect the presence of active virus by detecting virus proteins directly.

Antibody lateral flow tests for SARS-CoV-2 are produced as test kits used by a specialist rather than by patients themselves. They need a drop of patient blood, either from a vein or from a small finger prick, similar to a finger prick test used for blood sugar monitoring in some types of diabetes.
These types of tests work very differently to RT-PCR and LAMP techniques and detect the patient’s immune antibody response to the virus instead of detecting the virus itself.
Lateral flow antibody tests can be done rapidly and the tests can be produced cheaply, so various diagnostics companies are working hard to develop lateral flow tests for SARS-CoV-2.
A major advantage for this type of test is also the ability to see if patients are presently infected or have recovered from COVID-19 even if they have fully recovered and cleared the virus months ago. However, it cannot differentiate between an active and a previous infection.

How it works
Lateral flow immunoassays for COVID-19 are simple tools that can detect antibodies in the blood.
A small sample of patient blood is gotten from a vein or from a finger-prick by a scientist and dropped onto a spongy pad within the test device. A few drops of a diluting liquid called a ‘buffer’ are added to help the blood sample flow across the device.
As the sample moves through the device, antibodies against SARS-CoV-2 that are existent in the sample will attach to chemicals in the device, capturing the antibodies on the test and control lines. This capturing and binding process leads to a colour change along the test and control lines which can be seen by eye, producing one, two or three lines depending on the type of antibodies that are present(IgM or IgG).

What does the test detect?

Lateral flow immunoassays for SARS-CoV-2 detect two types of protective antibodies that are produced by the body when the immune system identifies a foreign structure, in this case SARS-CoV-2, the virus causing COVID-19.
These antibodies help fight the disease and stay in the blood for months after the virus and disease is cleared. The presence of antibodies in the body is usually referred to as immunity or that a person is immune to a virus, as these antibodies protect against re-infection and return of the same disease.
When we are infected by virus, our immune system generates early `prototype’ antibodies (IgM) with intermediate strength binding to virus, that are able to start working to clear virus about 5 days after a new infection. Usually, at 8 to 10 days after infection, IgG antibodies with high binding strength, can work to help more rapid virus clearance. Antibodies act by generating a matching contoured surface to stick to foreign antigens, using a refined selection process to amplify antibodies with the best surface match and strongest binding.

Antibody lateral flow immunoassays can be made to detect IgM or IgG alone or both together.

Antigen lateral flow immunoassays are an even newer technology with extra scientific and technical challenges which means they are not likely to be developed during the pandemic period. These antigen assays detect the virus directly without the amplification steps of RT-PCR and LAMP, and like those tests are only able to detect existing active viral infection but not past infection.

What does the result mean?
Antibody lateral flow immunoassays identify antibodies to the virus in the blood. They don’t detect the virus itself. The ability to detect the immune system response dependably using only one sample (blood) is a big advantage, as is the amplification of the detection signal generated by the body immune response. Using the antibody response alone does not allow distinction between individuals who are presently infected and those who have cleared the virus infection.
Antibody tests provide a huge important ability to detect past infection with virus to identify people who were asymptomatic, people who have cleared the virus and so no longer risk being infected or spreading the virus to others. In addition, antibody tests are important for assessing population spread of the virus and the level of ‘herd’ immunity in the population. This is essential for understanding the potential consequences of lifting or enforcing measures to control the virus such as quarantine, social distancing, school and workplace closures.
The antibody IgG and IgM lateral flow immunoassay tests are not difficult to read:
A control line must appear to show that the assay has worked properly.
Then, test lines will show if either of the antibody types are found in the sample. The presence of lines for IgG or IgM, or both indicate a positive test – indicating that the patient has been infected with the COVID-19 coronavirus.

Advantages and limitations

Advantages:

  • Lateral flow assays are very quick per patient, giving results in just 15 minutes.
  • Testing levels of antibody in blood permits a single patient sample from one accessible part of the body where sampling is non-invasive to be tested for presence of virus.
  • These tests need very little training to perform and don’t rely on specialist laboratories or scientists to analyze.

Disadvantages:

  • The technology is new and the evidence for its accuracy in coronavirus diagnosis is still being assessed.
  • Thus far, available lateral flow tests can only determine if a patient has at some point been infected with COVID-19. Further testing would be required to check if a patient is presently infected. Future versions of this technology might allow scientists to detect current infections.
  • Lateral flow tests are more expensive and takes a lot of time for large batch testing than specialist laboratory based antibody tests such as ELISA.

Enzyme-Linked Immunosorbent Assay (ELISA)


Technology overview
An Enzyme-Linked Immunosorbent Assay (ELISA) is a common biochemical method that can be used to detect antigens or antibodies, depending on the type of test used.
ELISAs use enzymes linked to antibodies that can attach to the molecule that is being tested for and cause a colour change that can be measured by a specialized machine. The strength of the colour change gives scientists an idea of the number of molecules of interest in the sample.
ELISAs can be done as standard batches of up to 96 assays completed at the same time, allowing cheap and time effective method for batch testing of large numbers of patient samples at the same time. This technology could help accelerate the number of patients that can be tested for SARS-CoV-2. The most effective ELISA assays in checking prior infection detect antibodies against SARS-CoV-2. Future ELISA could be used to test for active virus infection by detection of virus protein (antigen) testing, but this testing will not be as accurate and is not proven yet.

How it works
An ELISA detects antibodies formed in patient blood as a result infection with SARS-CoV-2. The entire test can be done in one tube or well and involves mixing patient samples, antibodies, antigens and enzymes together with a colour changing molecule. 

What does the test detect?
ELISA tests to detect antibodies are detecting the antibody reaction to COVID-19 infection.
Detecting antibodies to SARS-CoV-2 could tell a scientist if a patient has been infected with COVID-19, either presently or in the past. However, infected patients will not be noticed immediately on infection, but only when the immune system to the virus can be discovered in blood, approximately 5 days after infection for a test detecting IgM antibodies, which is about the exact time that symptoms/signs occur. Present facts propose once a person has been infected with virus, their immune system will avert a future infection with the same virus.
This antibody ELISA test provides very essential information for diagnosis, management and recovery from COVID-19 and will also help researchers evaluate how many people in the population have been infected, which is vital for planning infection control.

What does the result mean?
An antibody test using ELISA would display a positive result if the patient has antibodies to COVID-19. This might not mean that they presently have the virus, only that they have had it at some point. This is because antibodies stay in the blood even after the infection is gone to help provide the body with immunity if they come into contact with the virus again.
A negative result would mean that the patient has not been infected with COVID-19 and may have no resistance against it.

ELISA antigen tests may be developed in the future to detect existing infections. Such an antigen test using ELISA would display a positive result (colour change) if a patient has COVID-19 in their blood. This would show that the patient is currently infected with the COVID-19. A negative result (no colour change) would show that no COVID-19 antigens were found in the patient’s sample. This could mean that the patient does not have COVID-19. It might also mean that they are too early in their infection to be positive. If they have symptoms of COVID-19 they should be tested again a few days later to be sure.

Advantages and limitations

Advantages:

  • ELISA is a simple and inexpensive laboratory technique.
  • ELISA is well-known and documented within science and medicine.
  • Results can usually be produced within 1 to 3 hours of taking a patient sample.
  • Because it is so quick to carry out, it can be done in a hospital laboratory, reducing the time to diagnosis.
  • ELISA testing can be done on multiple samples at once, so it can be used for rapid testing scaled up to test larger numbers of patients.

Disadvantages:

  • ELISA tests are not yet well established for SARS-CoV-2 COVID-19 testing, although several companies are working hard to produce them and test them in patients.

CONCLUSIONS

  • Four main types of tests are being used or developed to test for SARS-CoV-2, the virus causing COVID-19.
  • These tests are at different stages of development, authentication and production.
  • Each test type has its own different advantages and disadvantages inherent to the underlying technology.
  • A mixture of testing types used at different times may be valuable for patient management and population pandemic control of COVID-19.


DisclaimerThe information provided herein is for patient general knowledge only and should not be used during any medical emergency, for the diagnosis or treatment of any medical condition. Duplication for personal and commercial use must be authorized in writing by Surjen.com.


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