Throat Swap for Lateral Flow with Symptoms?

Reuters reported that PCR tests of the saliva from 29 people infected with Omicron test detected the virus on average three days before nose samples were positive in antigen, or so-called lateral flow, tests.

They comment that:

"In general, rapid tests have a lower sensitivity than lab-processed PCR tests, meaning they produce more false negatives. But if you test positive, you almost certainly have COVID-19, making antigen tests a powerful tool in tackling the pandemic as demand for PCR tests due to Omicron overwhelms laboratories."

"In Israel, a top health official has said people self-testing for COVID-19 should swab their throat as well as their nose when using rapid antigen tests, even if it goes against instructions issued by the manufacturer."

"Some other countries, including the United Kingdom, have approved rapid antigen tests that swab both the throat and nose, or just the nose."

What is really interesting is that my sister brought back some tests from a holiday in September 2022 and the Lateral Flow Kits are identical, but the instructions are different - and say to swab the throat.

It appears that what matters in instructions given by our government are to follow the nose swab only - because that is what the tests we have here are approved to do - regardless of whether in fact they were not tested but would work with throat samples.

Now scientists are beginning to question the efficacy of nose-only tests. Professor Irene Petersen, of University College London, said she had been “trying to get an understanding of what’s going on” after infected people picked up on the possible defect with LFTs" She said this could be because the virus “may replicate in your throat and then your nose”. Professor Petersen said: “To me, it seems as though some people may have an infection in their throat before they get an infection in their nose. It seems a question about how Omicron establishes itself in your body and that appears to be different than previous variants.”

Professor Tim Spector, lead scientist for the Zoe Covid study, agreed, saying: “As well as knowing about cold-like symptoms – always swab both your throat as well as your nose if you want an accurate LFT.

Professor Jennifer L. Rohn, a cellular biologist in London, has said a negative lateral flow test does not always mean you do not have Covid as she received an incorrect result. The doctor has advised people displaying symptoms to still add the throat swab as an extra precaution, regardless of the instructions.

She said in a tweet: "Today, with the 'wrong' (i.e. cold) symptoms and after a string of negative LFTs, I finally took Twitter advice and swabbed my throat as well as my nose (no mean feat with that diddly stick): "If you think you might have COVID, consider adding the throat sample. Just for the avoidance of doubt - the test I used was FlowFlex, one of the UK government-provided LFD kits. These instruct the user to perform nasal sampling only. Other kits are designed for dual tonsil/nasal sampling. My suggestion is to perform dual even for former."

Another report from South Africa similarly found that saliva swabs conducted via a PCR test were more accurate at detecting the Omicron variant than the nasal swabs. Where those nasal swabs caught all the Delta variant COVID infections, they missed 14 percent of the Omicron variant COVID infections — but the saliva swabs caught 100 percent of the Omicron COVID infections.

And now I can speak from personal experience. Despite developing a nasty cough and fatigue, and aches in my bones, my lateral flow tests persisted on Tuesday and Wednesday in showing negative results. On Thursday I took a small throat sample before the nose, and the lines showed up clearly as red. Evidently the symptoms which I suspected being Covid were - as a PCR test has shown - but the nose only samples did not pick up even the slightest trace.

Contrary to Government advice, I would heed Professor Jennifer Rohn's suggestion, and if you start showing symptoms of what may be Covid, swab the throat as well. Otherwise you may have a false sense of security.

My symptoms have not got worse, and after a day in bed, I feel still poorly but better for the rest. I have, incidentally, had two vaccines and the booster.