Have I had Covid-19 in the past?
Covid-19 Antibody Blood Test (IgG testing, not IgM)
- For those aged 12 and over
- Short clinic visit, by appointment
- Small blood sample taken from your arm
- Result e-mailed to you, usually in 48 hours
- €135 in total (appointment, sample-taking and communication of results to you).
Who is the Covid-19 Coronavirus antibody test not suitable for?
- Those with current infection (the test will provide a negative result). If you are in this category, you must follow these HSE instructions: Symptoms of Coronavirus
- Those who have had the infection in the past 14 days (the test will provide a negative result). If you are in this category, you should be following these HSE instructions: Symptoms of Coronavirus
- Those who have arrived in Ireland from another country in the past 14 days. You should be self-isolating and following these HSE instructions: Travel and Coronavirus
- If you live with someone who has current Covid symptoms or a current Covid diagnosis. You should be self-isolating and be following these HSE instructions: Restricted movements for close contacts
- At our clinic, we are not offering this test to those aged under 12 years of age.
The Covid-19 Coronavirus post-infection antibody (serology) blood test.
We are able to perform blood testing in those aged 12 years and over to see if you have had Covid-19 infection. This is not the PCR nose/throat swab test for to screen for current, active infection. The test we are offering checks if your immune system has encountered Covid-19 in the past few months, by testing a blood sample to see if you have developed an immune response (antibodies) to the virus.
What is the Covid-19 Coronavirus antibody test?
It is a blood test (IgG; manufacturer: Abbott / method: CMIA (Chemiluminescent Microparticle Immunosorbent Assay)) taken from the arm. The sample is processed at a laboratory. The test looks for IgG antibodies, made by your immune system, against Covid-19. This test works reliably only if it is done 14 days or more after you have had the infection.
How long does it take for the Covid-19 Coronavirus antibody test result to become available?
In the case of tests done in the morning on Mondays, Tuesdays and Wednesdays, about two full working days. For tests done at other times during the week, a more detailed estimate of the turnaround time for results to become available can be found here.
Who is the manufacturer of the Covid-19 Coronavirus antibody test?
Abbott, a well-known U.S. biotechnology company.
How accurate is the Covid-19 Coronavirus antibody test?
The Abbott test was evaluated by Public Health England in May 2020 (their conclusions can be found here, along with their assessment of other test brands). With the Abbott test, a 'positive' result means the patient has had Covid-19 (100% specificity). A 'negative' result is 93.4% likely to be correct in the first few months after infection (93.4% sensitivity; a small number of people who have had Covid-19 will get a falsely negative test result).
Update – 18th November 2020: new research is now saying that IgG antibodies will be present in 98% of patients at one month post-symptom onset and still be present in 90% of patients six to eight months later. Neutralising antibodies are present in 90% of patients six to eight months post-illness. Click here to read an article about this in the New York Times. A pre-print of the paper in question is available here.
One group of people where a 'negative' result would lead to a theoretically lower than 93.4% confidence about the reliability of the negative result are those who are immunocompromised (though being on powerful medications that include a number of immunomodulators). A definition of immunocompromised can be found here. The test will still work in this group but will be less reliable.
In summary, here are the reasons a patient who has had Covid might have a negative IgG antibody blood test result:
- Minimal or no antibody production due to an asymptomatic or a very mild infection, or due to being immunocompromised
- Decline in antibody levels after six months (relevant in a small number of patients who had a symptomatic Covid infection).
The vast majority of patients who had a symptomatic infection will have a positive antibody result and in 90% of these patients, will still be positive after six months.
What is the simplest way to characterise this test?
A positive result means you have had Covid-19. A negative result means you almost certainly have not had Covid-19.
Does proof of recent Covid-19 Coronavirus infection guarantee immunity?
No. Research internationally is ongoing and it is very much a case that 'the jury is still out'. If Covid-19 behaves like related coronaviruses, then based on the experience with those viruses, it is likely that a majority of those who have a positive 'recent infection' test will not be re-infected for months and possibly a year or more.
There remains significant uncertainty around exactly what proportion of recently infected people are protected from re-infection, for how long and whether it is definite that they cannot re-acquire the infection and re-infect others in the future. The 'recent infection' (antibody/serology) test is at its most useful when it produces a 'positive' result, because positive results with this test are so reliable.
Some patients will find a positive test result useful, particularly for administrative reasons related to international travel (travel visa applications) - because a positive test result will suggest that they are likely to have immunity on a temporary basis at least.