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Comment by autoexec | Hacker News Reader

The negatives can't really be trusted, but if they say you've got it, you've got it.

The home tests are still useful, if for no other reason than because a lot of people cannot get a test at all, or can't get one unless they have symptoms.

My insurance company is like that. At one point in the last year I'd recently been with someone who tested positive two days later, and while I felt fine, I wanted a test before visiting a highly vulnerable relative and was told the test would be entirely out of pocket since I wasn't feeling sick. People who can't afford a PCR out of pocket can at least try several at home tests for some piece of mind.

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> The negatives can't really be trusted, but if they say you've got it, you've got it.

All of these tests have a non-zero false positive rate, they're not definitive proof that you have COVID.

It is vanishingly small relative to the false negative rate. It’s safe enough to say that if a test says you have it, you can act as if you it.

Why would you act differently when you're experiencing symptoms but the test is negative, if you know the negative is (relatively) highly likely to be "false"? And why would you test if you're having no symptoms? To me it is a very definition of useless test - neither positive nor negative add anything to decision making.

Lots of people will do a covid test, or more than one, if they know they spent significant time close to someone with covid. If positive, they can then take measures to keep their family and others from getting sick.

> And why would you test if you're having no symptoms?

It's useful in cases where you know you've been recently exposed to the virus. You can test yourself and avoid becoming an asymptomatic spreader.

If you, feeling fine, test positive for the virus then you know to stay away from everybody. You may be able to get a PCR to confirm at that point, but even if you can't, you can be confident (especially if multiple at home tests come back positive) that you're infected and act accordingly. You can contact your doctor, you can watch yourself closely for developing symptoms, you can isolate.

If you test negative after repeated tests in that situation, it's still not super comforting because false negatives are so high, but if you can't get a proper test due to your lack of symptoms the at home tests are the best indication that you've dogged a bullet that you're going to get. Maybe be careful to mask up when you go out just to be safe, but at that point you can be somewhat sure (as sure you can be) that you aren't going to get everyone around you infected.

That's pretty far from ideal. Ideally, anyone could just get a free PCR test, but it's way better than nothing and nowhere near useless.

I agree through, if you have symptoms it's best to assume the worst even if the home test is negative and see a doctor for a PCR in case it is covid or for a diagnosis and treatment in the event that it isn't.

The "act as if you [have] it" really depended on your government's policy at the time.

I live in the Netherlands, and during the height of the COVID scare here and in the EU you needed e.g. a negative test taken days before every flight, before attending a concert etc.

So even if the false positive rate was say 0.05% that's for each individual test.

But that quickly adds up. I think I did on the order of 50 tests during COVID.

If your spouse needs the same that's a 0.05 * 50 * 2 = 5% chance that one test during that period was a false positive.

Which could be a relatively life-changing event, e.g. the difference between a nice holiday, and being locked up in a quarantine hotel for weeks on arrival.

There were other ways those relatively small false positive numbers could cascade upwards, e.g. policies recommending that if anyone you've recently met had COVID, you should also quarantine.

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