Why home antibody tests for coronavirus have been taken off the shelves
The Medicines and Healthcare products Regulatory Agency (MHRA) called for a temporary halt on all home antibody tests on May 27th. All people who have taken the test are told to not consider the results as reliable. Before we get into the reason for this, we’ll explain how the home antibody tests work.
How does the coronavirus antibody test work?
An antibody test can detect if someone had coronavirus before and if they’re recovered from it. A positive result means a person has had coronavirus in the past, while a negative result indicates they’ve never had it.
If you use a home test you prick your finger and collect your blood, this blood sample will then be sent to a lab. The lab will test your blood for antibodies to SARS-CoV-2, which is the virus that causes COVID-19.
There are two types of antibodies and the test will look for one or both of them. First there is the IgM antibody, these happen early in an infection. Second there are the IgG antibodies, these are more likely to show up later, about 7 to 10 days after the symptoms start. IgG antibodies normally stay in your blood for a long time after an infection goes away. For coronavirus however, it’s not known how long these will stay in your blood.
‘We‘re not yet in a position to say that those who test positive in these antibody tests are immune for coronavirus.’ Matt Hancock mentioned in the daily briefing from Downing Street, which is important to keep in mind. There are multiple cases where people have been infected with COVID-19 twice.
How is it different from a PCR coronavirus test?
A PCR coronavirus swab test can only tell if a person currently has COVID-19. Not if they’ve had it in the past. This test can be done by taking a swab from your throat. The antibody test determines whether you’ve had coronavirus in the past, it won’t tell you if you’re currently infected. This test is done using a blood sample.
Why are the home antibody tests put on hold?
Public Health England (PHE) has approved the first antibody test, manufactured by Roche. As many of the finger prick antibody tests use the same technology in their labs as Roche, some providers wrongly claimed their kits as PHE validated. But these home tests are not yet regarded as effective.
Which is why all antibody testing services that use blood collected by a finger prick have been temporarily stopped. This is until the home collection of this type of sample has been validated for use with these lab tests. Using the unvalidated sample types can lead to unreliable results. Which is why the MHRA is working closely with these labs and test manufacturers to resolve this. Everyone who has done one of these tests in the past should consider their results unreliable.
It’s also important to consider that antibodies are usually associated with immunity, which is not the case with the coronavirus antibody test. People who get back a positive result from the test might think they’re immune to the virus and that it’s ok for them to break social distancing measures. The antibody tests are said to be essential for people to go back to work, however there is no certainty that people won’t be able to get infected again, so at this point the tests can’t stop the lockdown procedures. Rightangled has opted out of offering antibody tests in the first place, you can hear more about the reason for this in the LBC radio interview with CEO Abdullah Sabyah. To hear this interview please click here.
However, antibody tests administered by healthcare professionals have not been stopped by the MHRA, these tests use blood from the veins. These tests are currently still being used.