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How Does COVID-19 Testing Work?

Here's how testing for COVID-19 works in the Cayman Islands. 

 

Who Can Get Tested For COVID-19?

In April, we expanded our testing protocol so your doctor can decide if you need to be tested for COVID-19 without needing to refer to the World Health Organisation (WHO) criteria.

While the most common symptoms are shortness of breath, coughing, fever and loss of smell and taste, we have also had asymptomatic people who tested positive for COVID-19 in the Cayman Islands. The word asymptomatic means that you have no symptoms at all; therefore, the regular symptoms we would expect are not present and the person may otherwise feel and look healthy but still be infectious.

With this in mind, the Government is also screening healthy individuals from a cross-section of the population to allow us to understand the spread of COVID-19 in our communities.

Nonetheless, if you believe you have COVID-19, please contact your General Practitioner by telephone.

Public Health or your GP can advise you if you need a test, and direct you on how to book this.

 

How Are The COVID-19 Tests Done?

The tests are done by taking a swab using what looks like a long cotton bud in the nose or throat. The swab is then sent to a lab for testing in one of a number of hospitals in the Cayman Islands.  

 

What Methods Of Testing For COVID-19 Are Offered In Cayman?

Right now, there are two main kinds of tests for COVID-19 available:

  • Genomic, which looks for the genetic material of a virus (also called molecular testing, using a polymerase chain reaction)
  • Immunological, which looks to see if your body has had an immune response to the virus (also known as serological)

As of 16 March 2020, the Cayman Islands runs genomic (molecular) testing for the presence of the SARS-CoV-2, the virus responsible for the COVID-19 disease using a PCR (polymerase chain reaction) machine. This is the current 'gold standard' for COVID-19 diagnosis but only works when someone has enough virus in their body to detect it.

In June 2020, the Health Services Authority and Health City Cayman Islands announced they would also begin immunological testing locally.

 

How Does Molecular Testing For COVID-19 Work?

Molecular testing uses samples taken from the nasopharynx (from the back of the nose and throat) to test for genetic material relating to the virus responsible for COVID-19, which is called SARS-CoV-2.

All living things contain some kind of genetic material.

  • Humans have both DNA (deoxyribose nucleic acid) and RNA (ribose nucleic acid) in various parts of their cells, but the principal genetic material for reproduction is DNA
  • The COVID-19 virus has viral RNA as its genetic material

Molecular testing looks for the viral RNA specific to COVID-19 (think of it like a bar-code) in the samples taken from people. 

 

Steps for Molecular Testing

 

Step 1: Swabbing

When swabbing happens, a sample is taken from the back of your nose and throat area with a swab. This process is fast. It may feel weird or uncomfortable but it is often painless.

We know that COVID-19 virus specifically likes the environment of our airways, which is why we take the sample from the nose and throat. 

 

Step 2: Inactivation

A viral transport medium (chemical) is added to the sample and it is transported to a lab. Once in the lab, it is deactivated in a biosafety cabinet (a containment device used in laboratories working with infectious agents).

 

Step 3: Extraction & Transformation

Different chemicals and enzymes can open up viruses to expose their genetic information so that we can look for exactly the genetic material that makes COVID-19 unique.

During extraction, a technician adds these chemicals to the sample and spins it in a centrifuge machine.

The viral RNA is then combined with enzymes that make what could be called a carbon copy of the genetic material. 

 

Step 4: Amplify The DNA

The genetic material is then doubled many times over (sometimes billions of times) and this takes a few hours using the polymerase chain reaction (PCR) machine.  When enough genetic material has been created by multiple times of doubling, markers begin to glow which will detect the presence of the COVID-19 genetic material. The PCR machine will pick up these markers which form the results of the process.

 

Step 5: The COVID-19 Results

The results are not a straightforward ‘yes’ or ‘no’ and are usually presented on a graph and require a specialist to interpret.

That said, if you have viral RNA detectable, the test will return as positive. Otherwise, the test will report that nothing was detected.

In the case of COVID-19, there may be times when there was not enough viral genetic material in the swab to detect the presence of the virus, even though someone is suffering from the disease. All tests need to take into account the clinical condition of the patient.

All laboratories undergo a number of quality assurance processes both internally and externally.  The HSA has been involved with a quality assurance project with the World  Health Organisation but the results of this are not yet available.  The Doctors Hospital has been following guidance from PAHO for their quality assurance which has involved some cross checking with the HSA.  Sample tests from both organisations have also been sent to the regional Public health laboratory, CARPHA, in addition.

 

Step 6: Retesting

If you test positive for COVID-19, in order to make sure you are no longer infectious, you must have two negative results, 24 hours apart, for COVID-19 at least 14 days after your initial positive test or when you no longer have symptoms (whichever is the longer).

If a result returns as positive, you still have viral material that is in your body and you need to remain isolated until the lab can confirm two negative test results.

 

What About Immunoglobulin Testing?

The Cayman Islands commenced immunoglobulin testing on Tuesday, 16 June 2020 as part of Public Health monitoring to COVID-19. Immunoglobulin tests (also known as antibody testing) commonly look for the presence of two different groups of immunoglobulin known as IgM and IgG, which are usually present in the body after someone has been infected by something and who has begun to build immunity towards the disease.

IgM is normally the first antibody to be made in response to COVID-19, while IgG produces longer lasting immunity and an immune memory. Everyone has a different response to how their body’s immune system will react to any virus, so just because you might have had COVID-19, it is possible that your body might not mount an immune reaction which we will be able to measure.

IgM and IgG image

Credit: Google images.  Please note that this is purely illustrative and should not be used as a primary reference.

This test looks for these antibodies by collecting a sample that is normally in the blood and can provide quick results.

 

Do We Use Immunoglobulin Testing?

At the moment, testing priority for immunoglobulin tests will be for healthcare workers, known positives and frontline workers who were already screened. Immunoglobulin tests will be conducted at the Health Services Authority and Health City Cayman Islands.

Once the priority groups have been tested, immunoglobulin testing will then be conducted across sample sized groups throughout the islands which will aim to give us a good indication on the level of infection in our community.

Although Public Health England (PHE) has recommended the use of immunoglobulin tests, this test does not necessarily mean that you are immune to COVID-19. It is important to note that the immunoglobulin testing give slightly different results to PCR machines as PCRs shows you have an active infection, whereas the immunoglobulins give a longer view over time of your past exposure.

The public is still recommended to follow public health precautionary measures to protect yourself and others.

 

More Questions?

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Cayman Islands Government, Government Admin Building, Grand Cayman, Cayman Islands, Tel: 345 949 7900

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