Thread by @RPLerias

This is the anedoctal tale of six rapid antigen covid tests (RAT) from four different brands taken by the same person, within a 2 hour time period and how the results were quite diverse. It reinforces that a negative RAT doesn't mean a person isn't infected. Act accordingly.
1/

The tests were taken in order from left to right: A B A B C D. Each letter represents a different brand. The A tests are positive, the Bs negative, C and D are ver faint positives (the C + is extremely faint but is there).
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The tests were done because the result of the first was an unexpected and undesired surprise. After the first positive, we did a counter test that was negative, which led to a repetition of these tests from the same brands, confirming the previous results.
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These results were also a surprise because I have used the Panbio test since September 2020 and had the opportunity to cross check with PCR tests on different occasions and was very happy with its performance. But here it was outperformed by cheaper alternatives.
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The FlowFlex test by Acon Biotech had the best result. It was able to give clear positive results in someone virtually assymptomatic, at the start of infection. It is the most widely available and cheapest test here in Portugal at the moment, so it's good to see it perform.
5/

It was also a surprise that tests with short, thick swabs (A/D) outperformed tests with long thin swabs (B/C). I've preferred long thin swabs because they allow sampling the throat and go deeper in the nasal cavity. But here, the short swabs used in the nose alone did better.
6/

Maybe the short swabs absorbed more material from what must have been the shedding area at that moment. Or maybe the tests have different sensitivities for the current circulating strains. I don't know for sure. But the negative results from a trusted test were an eye opener.
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I have in the past made risk assessments based on negative RATs that I would now feel less confortable with. It's true that these RAT results likely mean the person wasn't very infectious then. And RATs are an extremely useful tool that allow decisions to be made in real time.
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But one can become over confident with negative RATs. So, if the RAT negative result disagrees with the person symptoms or risk contact, don't make decisions based on RAT alone. As in this case, RATs can produce false negatives, so always interpret a negative result with care.
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And don't be shy in using different brands at the same time when testing. As it was the case here, if we had used the Panbio alone we would't had isolated as early as we did. And that early isolation could have made the difference between getting infected or not.
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This has been a valuable lesson for us. Buy tests from different brands and test generously. And remember to integrate the test result with all the other information you have - symptoms and time from previous risk exposure - before making risk assessment decisions.
(End) 11/11

It should be said that the swab was used in both nostrils and inserted almost completely in at least one of the nostrils, and very thoroughly circled before performing the test.