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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?

We have recently 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 or the 24-hour Flu Hotline on 1-800-534-8600 / 925-6327 (Flow) / 947-3077 (Digicel) or email flu@hsa.ky.

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 of March, 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.

 

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 disease, 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.

In order to confirm the quality of test results, all processes are regularly tested for validation in the Cayman Islands. We also send all positive and inconclusive results for cross-checking to our reference laboratory in Trinidad, CARPHA, along with 10% of negative cases.

 

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?

Currently, we do not carry out this testing in the Cayman Islands.

Immunoglobulin tests 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 begins to build immunity towards the disease.

In other words, antibodies such as IgM and IgG are produced by the body to fight a virus.

IgM is normally the first antibody to be made in response to COVID-19, while IgG produces longer lasting immunity and an immune memory.

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.

 

So Why Not Use Immunoglobulin Testing?

At the moment, immunoglobulin tests are not yet giving accurate and consistent results and so are not being recommended by major public health agencies such as the WHO, PAHO (the Pan American Health Organisation) or Public Health England. However, they are likely to improve with time. They also 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.

Immunoglobulin testing will no doubt prove useful in combination with molecular testing after you are certain that a person is not infectious. At some point, the test for IgG may tell us whether a person has immunity; unfortunately, it is not yet known how long this immunity lasts.

 

More Questions?

Visit our FAQs page or email neoc@gov.ky 

Tags: testing

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

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