Coronavirus Antibody Test
Do I have Covid antibodies due to either past infection or vaccination?
Covid-19 Antibody Blood Test (from 29th March 2021, we have been using the Roche spike protein, combined IgG/IgM test)
- For those aged 12 and over
- Short clinic visit, by appointment
- Small blood sample taken from your arm
- Result e-mailed to you within 3 days (for samples taken after 1pm on Fridays: 5 days)
- €109 in total (appointment, sample-taking and communication of results to you).
- In use by us since: 29th March 2021
- Manufacturer: Roche (Switzerland)
- Test name: Sars-CoV-2 spike protein, combined IgG/IgM antibody blood test
- Processing laboratory: a large multinational lab in Dublin
- Sample type: blood sample taken by us from a vein in your arm
- How the result is sent to you: by e-mail direct to you from our doctor; you will receive a pdf of the test result plus an interpretation from our doctor of the result significance
- What the test tells you: whether you have detectable antibodies against Covid (specifically against the 'spike' protein on the surface of the Covid virus) due to either vaccination or past infection. The test detects IgG and IgM antibodies to the spike protein but does not distinguish between them, if they are present.
- What information appears on the test result: a numerical figure as to the amount of combined IgG/IgM Covid spike protein antibodies that are present (<0.8 U/ml = 'negative' and >0.8 U/ml = 'positive'). The IgM result is not presented as a stand-alone result.
- What you should read into the antibody quantity result: for now, nothing - there is no scientific consensus yet as to what significance can be read into the the numerical figure. Until more information about the significance of different antibody levels emerges, I do not recommend that you do repeat testing to 'track' your antibody levels (rising, falling), unless you are keen to do so.
What scenarios should lead to a positive result?
Past Covid infection or past Covid vaccination. Current evidence (mid-July 2021) is showing that about 95% of patients who have had a previous Covid infection will have detectable antibodies 15 months later. It is likely that the great majority of patients who have had a Covid infection even as far back as late 2019 should still have detectable antibodies now.
If you're having the test done to see whether you have evidence of having responded to the Covid vaccine, how long should you wait after the first dose of vaccine before having the test done?
At least 14 days and better still, 28 days.
What makes this test more useful than the Abbott (nucleocapsid protein) test we used between May 2020 and late March 2021?
The Abbott test remains negative after vaccination and works only if you have had Covid infection.
The Roche spike protein test picks up evidence of vaccination as well as evidence of infection.
What are the weaknesses/limitations of this test?
- The antibody quantity has no meaning, currently (this will probably change, as more research is published in the scientific literature)
- If you receive a positive result and you have been vaccinated, we won't be able to tell you if you have also had Covid infection in the past or not
- If you receive a negative result after having been vaccinated, we won't be able to tell you if you have protection or not (it remains unknown, for now, whether a negative result post-vaccination definitely means 'no immunity' or not)
- An IgM-only result is not displayed and the result cannot normally be used for travel purposes
What is the strength of this test?
Some patients who have been vaccinated and receive a positive result will just feel 'better' knowing they have a proven antibody response. There is nothing wrong with wanting this psychological reassurance. In particular, some patients who are receiving immunosuppressive treatment and have been vaccinated against Covid, like to know if the have detectable Covid antibodies.
For those who have not been vaccinated against Covid and who want to know if they might already have had the infection, the test is reliable for determining this. About 95% of those who have had a Covid infection should have detectable spike protein even fifteen months later (an example of the research evidence supporting this is here: https://www.medrxiv.org/content/10.1101/2020.11.20.20235697v1)
How accurate is the Covid-19 antibody blood test?
A positive result provides near-100% certainty that you have either been vaccinated against Covid or had the infection or both (but does not distinguish between those two scenarios)
A negative result means you do not have detectable Covid antibodies; if you have been vaccinated, it's not yet known whether this means you are definitely unprotected. If you have not been vaccinated against Covid, a negative test result means there is an 80% – 90% chance you have not had Covid infection.
Who is the Covid-19 antibody blood test not suitable for?
- Those requiring a result for travel purposes (you should probably be doing a P.C.R. or Rapid Antigen test instead)
- Those with current infection (the test will provide a negative result, unless you have already been vaccinated). If you are in this category, you must follow these H.S.E. instructions: Symptoms of Coronavirus
- Those who have had the infection in the past 14 days (the test will provide a negative result, unless you have already been vaccinated). If you are in this category, you should be following these HSE instructions: Symptoms of Coronavirus
- Those who have arrived in Ireland recently from another country and for whatever reason, under Irish Government/H.S.E. rules, should be self-isolating. You can check to see if this applies to you here: Travel and Coronavirus
- If you live with someone who has current Covid symptoms or a current Covid diagnosis. You should be following these H.S.E. instructions: Restricted movements for close contacts
- At our clinic, we are not offering this test to those aged under 12 years of age.