So it seems I must see a doctor and get a prescription for a PCR test. The problem is that is getting harder to get this kind of tests, as they are running out of the chemicals.
Thank you. Obrigado.
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The false negative narrative is overblown. Even with the home tests, you will eventually test positive, and within a day or two of when you test positive with a PCR test. Itâs just that those hours are critical for keeping contagious people from infecting others.
My understanding is that if you have been symptomatic for 48 hours and still test negative for several tests, you can be highly confident you are actually COVID negative.
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How many tests?
People are saying a single PCR test is costing almost US$ 37.00 and is very hard to get one these days.
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While there is some evidence that some lateral flow tests donât work as well with the Omicron variant, there is no reason to panic.
If you can get a PCR, get one. Still, if you had a lateral flow device with those symptoms and it is negative, it is still much more likely that you havenât caught COVID-19 than the other way round. Especially during the first days of illness.
ETA:
@DukeTrout is talking about lateral flow tests, I think. Also known as rapid tests, antigene tests or POC (point-of-care) tests.
If you have symptoms and test every day, or every other day (depending on how many ar-home testkits you can get/afford), you can be quite sure not to have COVID-19, and especially not to be infectious.
Do it best after getting up, in the morning, before eating and drinking, and after blowing your nose a bit without wiping everything into a handkerchief.
This advice is based on what I learned from listening to Sandra Ciesek on the German-language Das Coronavirus-Update podcast when she commented performing and related the results of their studies of lateral flow devices in 2021. Sheâs a gem of science communication.
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Thank you. It is what I most fear. I don´t want to spread this disease and infect my friends, coworkers and loved ones. I don´t want to infect even that annoying people in the supermarket cashier line.
Although the government wanted to distribute these test kits, they âforgotâ to do all the paperwork and didn´t send the documents to the regulatory agency. So, these tests aren´t approved yet.
Sometimes I have this feeling they don´t want to help the population.
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But isnât âkeeping contagious people from infecting othersâ the main reason why people are being asked to do home tests in the first place?
That may or may not be true for omicron. Do you happen to have a source with data that you can point to?
I know itâs anecdotal but my brother-in-law who works for a test manufacturing company (therefore had many tests available) became symptomatic on a Friday and didnât test positive until the following Monday, getting a couple false negatives in the meantime. Most people wonât have that many home tests available.
So far this is the only actual study Iâve read comparing antibody vs PCR test efficacy for Omicron.
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Supreme Court blocks Biden vaccine mandate for businesses, backs health-care worker rule
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Ireland says âhold my beer!â we got to that stage, over 50% positivity and really difficult to get tested, just after Christmas. I wasnât as lucky as you - I met two people one recently recovered and one with a negative antigen test that day. Got the contact tracing call shortly after I came home from my booster. Shittily sick since 20th December. Everyone in the house got it. Mostly over it now though I cough a lot, canât really go up stairs without a coughing fit. Talking makes me cough a lot too. Some days the lungs hurt.
If this is the mild version itâs some motherfucker at full strength!
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A single home test/antigen test is 80-90% sensitive. A second test raises that figure statistically to 96-99% sensitive and a third to 99.2% to 99.9%. Sensitivity also increases as viral production in the upper airway increases, which produces more antigen particles to detect.
Ideally, an antigen test will detect infection as soon as one starts to shed any viral particles at all, but thereâs a trade-off between sensitivity and specificity along with limitations of lateral flow test indicators. But once a person is symptomatic, there should be plenty of antigens for the test to detect with VERY high sensitivity within 3 tests. However, thatâs in the first few days of symptoms. Afterwards, antigens in the upper airway decrease and it gets harder to detect.
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Thatâs expected based on the statistics I posted above. Some people will take a full 48 hours and three sequential tests 24 hours apart before they test positive. The answer is, if you are at all symptomatic, isolate until you have those 3 sequential negative antigen tests or a single negative PCR test.
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Fuck
And fuck again because one wasnât enough words to post
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The false negative narrative is overblown.
Itâs just another brick in the wallâŚ
My main current concern (no really) is schools, where entirely due to political inertia and ineptitude, part measures are in place. Too many people are catching COVID from a quick trip to a supermarket or Canadian Tire.
Maybe itâs a side effect of having been raised in a nuclear 
family, perhaps itâs professionally watching stupid financial risks blow up in businesses, but Iâm not a fan of part-measures when full risk mitigation measures are only a question of discipline and some additional time.
Simple binomial probability says our familyâs risk of a case of Long(er) COVID is at least 15%, maybe as high as 35%, if Omicron rips through my household. Care to roll a saving throw on a d6 
?
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PUTZ!
I hope you get well soon. I hate people who downplay this disease.
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That would be true if medical testing behaved according to statistics that assume complete independence between tests, but it doesnât. The test subject is the same each time, and factors that affected the first test still may be present. A common scenario is medications interfering with an assay. With COVID, if the strain infecting a patient isnât readily detected by a rapid test or if sampling technique is poor, the second and third tests will have limitations like the first.
Three negative tests from the same patient, therefore, does not mean no infection 99.2 to 99.9% of the time. Three negatives would be reassuring, but the clinical picture always has to be considered.
This is why I hate at-home testing to rule out the disease. The risk of false reassurance is just too great.
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That reminds me:
Kindergarten around the corner. Taking care of about 90 kids. Currently, only the 2 to 3yr olds and a forest kindergarten group are mostly separate, about 70 kids are mixing freely.
They now think about changing that.
However, due to staff limitations, they can only form two groups of about 40 kids each, now including the 2-3yr olds.
They were asking the parent council if they agree. Downside: if just two of the staff get sick, they cannot meet the legal requirements for kids/staff ratio and would have to limit opening hours.
Now, how do I advise the parents, on probability grounds⌠Iâm a bit slow tonight, I admit⌠Damn.
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I will have to go back to the studies establishing those sensitivity numbers, but I think all those factors are already accounted for in the stats. They werenât bench tests but real-world studies with real patients. The only one that isnât is the omicron variant sensitivity, which isnât definitively a confounding factor at this point until itâs studied in more depth.
ETA: Good news and bad news. The Johnâs Hopkins study on the BinaxNOW antigen test published in Decemberâ21 had an overall sensitivity of 81% in mostly real-world conditions. That includes sample collection by health care workers and test result interpretation by lay people (which they validated with QC).The bad news is that sensitivity was much lower for asymptomatic patients (71%) than for symptomatic patients (87%).
How much of a factor does sample collection play? Okoye et al at University of Utah performed a similar study but had college students collect their own samples. The result was 53% sensitivity. So, also bad news if youâre doing your own sample collection and you donât have health care or laboratory training.
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Bolsonaro, for example, locked info on his vaccination Record for 100 yearsâŚ
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How did all that brown nosing work out, Ron?
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Now, how do I advise the parents, on probability groundsâŚ
Back of the envelope? Iâd say take your probability of successfully spreading the disease as the chance of an infectious kid showing up. Each kid is a trial, but you only need one to infect the class. Youâre sampling without replacement but from a huge population, so no need to get fancy.
- Quick/dirty (1-(1-p)^n) with p=0.01 of an infectious kid says p~33% for 40 kids, p~60% with 90 kids. So you are down to half the risk for half the staff each. At that point it depends how well protected the staff are, but divide and conquer.
- With p=0.05, which is where Ontario
was around end December, the numbers arenât even worth looking at (87% and 98%) youâre toast, as far as exposing staff, anyhow.
Now⌠kids are all from the same neighbourhood so likely not independent draws. Vorausgesetz guter deutscher Ordnung presumably infectious kids will be removed from the pool quickly upon discovery. 
Iâll bet no matter the model, that the probability of an infectious individual showing up remains the dominant factor. If you want to add staff probability of infection the quickest thing would be a Monte-Carlo simulation; lazy answer, I know, but easy and quick.
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