Just as we thought we understood Covid testing, along came omicron and raised a whole new bunch of questions. We asked Dr Andrew Lee, a reader in global public health, to answer them.
The UK government website ran out of lateral flow tests. Does that mean I can’t get one anywhere?
Lateral flow tests for home delivery in England were temporarily unavailable in recent days. Government ministers have stressed that this is not because of a shortage of the tests but because of an exceptional increase in demand for them that has outstripped the ability to deliver the tests.
This is reminiscent of the toilet-paper buying frenzy last year when people feared a shortage. It is likely that as the rush for tests settles, online access to the tests should quickly return to normal.
It’s important to note that you can still get a lateral flow test from your local pharmacy, as long as you have a collect code. Students and education staff may also be able to get tests from their schools and colleges and there are local community collection sites, such as libraries and mosques. Check with your local council for the latest information.
Do lateral flow tests work as well with omicron as they did with previous variants?
The UK Health Security Agency has tested the lateral flow devices currently in use and has reported that they do detect omicron and work as well as they did against other variants such as delta.
If I have symptoms and a negative lateral flow test, should I still get a PCR?
Yes. Anyone with Covid symptoms should get a PCR test, even if they have had a negative result on a lateral flow test. Compared with the lateral flow test, the PCR test is far more sensitive. This does not mean the lateral flow test is not good – they offer a rapid result and can detect infections when a person might be most infectious and likely to spread infection.
If both the lateral flow and PCR tests are negative, then you are unlikely to have Covid and the symptoms may be due to some other disease, such as infection caused by another winter virus.
Can PCR tests also detect the so-called stealth version of omicron?
Yes. It is important to stress that PCR tests for Covid will detect infections caused by all variants of Covid, including omicron and the so-called stealth version. Some PCR tests, such as reflex assay tests which are used for rapid screening of known mutations, use a set of “gene targets” to help identify which variant of the virus is present. The so-called stealth version of omicron doesn’t have one of the mutations that allows it to be identified by one of the gene targets, but the infection will still be detected by the other gene targets. It is therefore incorrectly labelled as a stealth version, as it is still detectable by the PCR test.
Can I do a PCR test at home? If so, how?
Yes. It is possible to order a PCR test kit to do at home. Anyone with Covid symptoms can order a home test kit through the government website. If you do not have Covid symptoms, you may still be able to get a PCR test kit if:
you are a contact of someone who has tested positive
you’ve been asked to get a test by a local council or someone from NHS Test and Trace
a GP or other health professional has asked you to get a test
you’re taking part in a government pilot project
you’ve been asked to get a test to confirm a positive result
you’ve received an unclear result and were told to get a second test
you need to get a test for someone you live with who has symptoms.
If I do a PCR, will I be told if I have omicron?
Not necessarily. Not all PCR Covid tests undergo a further set of tests to work out which variant has caused that infection. But neither is this information crucial. For the individual, it will not matter much which variant one has as the public health measures will be the same; that is, the need to self-isolate and to take precautions to limit the spread of infection. Also, in the coming weeks, it is likely that most infections then will be caused by omicron and not other variants.
How good are PCR tests at accurately identifying omicron?
As mentioned above, the PCR tests for Covid are pretty good at detecting Covid infections including omicron. But not all positive PCR tests go on to have additional tests to work out which variant is causing the infection. A proportion will be tested for a set of gene targets (genotyping), and some will go on to have a much more extensive analysis of all of the genes of the virus (sequencing). Sequencing will give the most accurate identification of omicron. Genotyping can also be very accurate when a gene target specific to this variant is used.
If I have a positive lateral flow or PCR test, what do I need to do?
In both cases, if you have a positive lateral flow or PCR test, you should isolate immediately. This is the most important step you can take that will help prevent the spread of infection to others. Self-isolation means you should not go to work, school or public places, you should work from home if you can, you should not go on public transport or use taxis, or go out to get food and medicine. You should not have visitors in your home, including friends and family – except for people who give essential care.
More advice is available on the NHS website.