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IgG Antibody Testing

What is COVID-19?

COVID-19 is caused by the SARS-CoV-2 virus. This virus, which can cause mild to severe respiratory illness, has spread globally, including to the Isle of Man. This illness is very contagious and although the usual symptoms (sore throat, fever or loss of smell / taste) are well known, it is also possible that some people may have had the virus with mild or even no symptoms.

What is the COVID-19 IgG Antibody test?

Antibody tests differ from the usual ‘swab’ type test, which tests to see if you currently have the disease.

This test is designed to detect antibodies against the virus that causes COVID-19. Antibodies are proteins produced by the immune system in response to an infection and are specific to that particular infection. They are found in the blood and so will require a sample to be taken from your arm.

Your sample will be tested for a type of antibody called immunoglobulin G (IgG).

This antibody develops in most patients at around two weeks after infection and remains in the blood after you have recovered although we do not presently know how long it may persist. If this antibody is found in your blood, it indicates that you may have had COVID-19 in the recent past and have developed an immune response against the virus. It is unknown at this point how much protection, if any, antibodies might provide against another infection with SARS-CoV-2. This means that having a positive antibody test does not mean you are immune to COVID-19 and the test result will not enable you to make any decisions, for example, about work or travel.

Why is my sample being tested?

You have been offered a test because:

  • You may have previously tested negative for COVID-19 but did have some symptoms that we would normally expect from people with the infection.
  • You have not had typical symptoms, but as many people are known to have had this virus and be asymptomatic, we are taking the opportunity to test people whilst they are having another, unrelated, blood test.
  • You have been in close contact with an individual suspected of or confirmed to have COVID-19; or you may have been otherwise exposed to the virus.
  • You have recovered from COVID-19.

Testing of your sample will help find out if you may have antibodies to COVID-19 and provide us with a greater understanding about the spread of the virus on the Isle of Man.

Our knowledge of the virus will grow as new scientific evidence and studies emerge. COVID-19 is a new disease, and our awareness of the body’s immune response to it is limited. We do not know, for example, how long an antibody response lasts, whether the antibodies produced are effective in neutralising the virus, or whether having antibodies means a person cannot transmit the virus to others.

What are the known and potential risks and benefits of the test?

Potential risks include: 

  • Possible discomfort, bruising, infection or other complications that can happen during sample collection. Serious complications are very rare.
  • Possible incorrect test result (see below for more information).

Potential benefits include:

  • The results can help give you some reassurance that you may already have had COVID-19.
  • The results of this test may help us understand the spread of COVID-19 within the community.

What does it mean if I have a positive test result?

If you have a positive test result (antibodies are detected), you may have been infected with the virus that causes COVID-19 at some point in the past. There is still a small chance that the antibodies indicate past infection due to other coronaviruses.

The presence of IgG suggests that the infection happened weeks to months in the past. In some infectious diseases, having IgG gives immunity and protection from catching the disease again. In other diseases, this is not the case. With COVID-19, we do not know yet whether having measurable IgG gives immunity or, if it does, how long the immunity would last. How much it might protect you from catching COVID-19 in the future is unknown.

What does it mean if I have a negative test result?

A negative test result means that the antibodies to the virus that causes COVID-19 were not found in your sample. In most cases, this will mean that you have not been infected with the virus in the past. Some health conditions might make it difficult for your body to produce antibodies to an infection. However, there is a small chance for this test to give a negative result that is incorrect (false negative) in some people.

A negative result may occur if you are tested early after exposure to the virus and your body hasn’t had time to produce antibodies to infection. This means that you could possibly still have had COVID-19 even though the test is negative.

  • To ensure the safety of our patients and staff, please let us know if you have had a sore throat, fever or other symptoms within the last 2 weeks. If you are currently sick, please talk to your doctor about options for testing and care.