A traveler just brought Tonga its very first Covid case

Originally published at: A traveler just brought Tonga its very first Covid case | Boing Boing


Did they use the rapid antigen test on arrival? The departure tests are molecular PCR which are much more accurate, and the rapid antigen tests have a false positive rate that isn’t great. It may well be that the person doesn’t actually carry the virus. Quarantine is a good idea regardless, but Tonga may still be okay. While breakthrough cases obviously do happen, someone who is double-vaxxed and tests negative on PCR is pretty vanishingly unlikely to be infected.


Do you have a source on that? Everything I’ve read so far is that the issue with rapid tests is that they are less sensitive than the PCR tests. In other words a rapid test is more likely to give you a false negative than a PCR test. False positives with either are pretty rare.

It’s enough of a problem that the FDA issued a warning about it.


That’s basically the FDA suggesting people follow the instructions and avoid cross contamination. The relevant paragraphs are:

In general, antigen tests are not as sensitive as molecular tests. Due to the potential for decreased sensitivity compared to molecular assays, negative results from an antigen test may need to be confirmed with a molecular test prior to making treatment decisions. Negative results from an antigen test should be considered in the context of clinical observations, patient history and epidemiological information.

Like molecular tests, antigen tests are typically highly specific for the SARS-CoV-2 virus. However, all diagnostic tests may be subject to false positive results, especially in low prevalence settings. Health care providers should always carefully consider diagnostic test results in the context of all available clinical, diagnostic and epidemiological information. Test interference from patient-specific factors, such as the presence of human antibodies (for example, Rheumatoid Factor, or other non-specific antibodies) or highly viscous specimens could also lead to false positive results.

It doesn’t matter why the false positives are happening with that type of test, just that they are.

It’s hard to findout but I think it is unlikely, in NZ and Australia we are still predominately using the PCR for everything, in fact today is the first day in Australia that you can buy the rapid antigen test over the counter.
Obviously Tonga is its own country but tends to be pretty linked to NZ and Australia in terms of Health Services so most likely they are also using PCR.

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