Yes, pretty sure. Your linked Science article seems to relate to the usefulness of the CT value for predicting infectiousness/evaluating viral load; I didn’t say otherwise.
What I did say is that I don’t believe that CT values are sufficiently well correlated with time of infection that the CDC can take the high CT value of a single patient who last entered Taiwan four months ago (or whatever it was) and reliably conclude that the infection happened outside Taiwan.
In this case it seems to be that they assumed that the person can’t possibly have been infected inside Taiwan and therefore they were definitely infected outside Taiwan. Come on, you know that’s no kind of valid scientific logic.
I didn’t say I agreed that they couldn’t be infected in Taiwan.
What I’m saying is it’s still most likely they got infected overseas on the balance of probabilities .
Find out of if their relatives and close contacts have covid antibodies and I will agree they were most likely infected here. However I don’t think it’s likely a cluster just dies out by itself .
The Ct value literally just tells you how much viral material is present in the sample. It’s how many amplification cycles were needed to detect the target viral RNA. There’s no standardization between assays and things like sample collection can affect the result. Ct value alone can’t tell you when a specific person was infected.
The business guy who has been here for 3 months and gave a negative Covid test taken 3 days before his flight had a Ct value of 31 on his first test and 36 on the next one 1 day later. Doesn’t mean a sample taken the next day will be 41 or that a sample taken a day earlier would have been 26…
IgM is a clue to infection date because IgM titers decline rapidly. Like I said, positive PCR + positive IgM in non immunocompromised people = suspect a recent infection over a long past infection unless you have clinical presentation suggesting otherwise.
If you were a “clinical chemistry” expert you would know this.
Feel free to respond to the rest of it. (edit: I see you have now)
Are you suggesting that they can take the CT value of this patient (36, IIRC) and definitively state that the infection happened outside Taiwan?
I’d be interested to know how CT values typically vary over time, e.g., how many confirmed infected people show similar values one month, two months, etc. after infection, and what the variability is. But there’s no way they can take this single data point and say with confidence that it happened outside Taiwan.
Irrelevant.
You know less than you think about clinical diagnostics that is what I can tell you…It’s a highly specialised field in itself because of dealing with exactly these kinds of situations that commonly.arise in population wide screening . For every disease that is screened ovet a large population you’ll encounter the same issues. You’ll have the same problems with HIV…The same with Hepatitis C, B etc.
What is the cutoff on the high and low end in different populations ? How to design a study to set that cut off?
What’s the acceptable CV?
What’s the dynamic range?
How does it relate to the disease ? How to get consensus on the clinical implications ?
How to ensure consistent quality control ?
You need to understand how the huge numbers of people getting tested and also repeat tested means that you will definitely get some people with unusual immune responses pop up. They will be over the ‘minimum cut off’. Looking at how much over the minimum cutoff is also something to look at.
They may also be carrying a latent low level infection .
Of course I don’t agree with the definitive conclusion that the infection was acquired overseas though.
People who are not immunocompromised don’t have asymptomatic “latent low level” covid infections for 3-6 months. The rare cases of months long infections have been seen in people who are immunocompromised.
In covid?
I don’t think we understand that much to make a definitive statement one way or the other. There’s a lot of genetic variation out there.
Some people can’t be infected at all…maybe some people just struggle to clear it for whatever reason but are not generally immunocompromised .It’s a possibility . Maybe the antibodies they make are just not very good at neutralising the virus. Who knows.
My bet though is the raised IgM is most likely a false positive due to cross reactivity.
The PPV is the critical factor to look at here when screening across so many people.
It says the PPV is only 92 per cent when covid prevalence is just 5 per cent in the population .
So someone tests PCR, IgM, IgG positive, clearly indicating they had/have a virus, and with no evidence in hand you want to “bet” against the probabilities that their IgM positive is a false positive due to cross reactivity because…it fits what you want to believe. Thank goodness you’re not doing this professionally.
You don’t understand population wide screening.
Do you know what is PPV and can you read all the statistics above with confidence and understand what they mean in different situations , e.g. when covid prevelance is widespread, when covid prevalence is low and how that affects the PPV?
> When the prevalence of preclinical disease is low, the positive predictive value will also be low, even using a test with high sensitivity and specificity. For such rare diseases, a large proportion of those with positive screening tests will inevitably be found not to have the disease upon further diagnostic testing. To increase the positive predictive value of a screening test, a program could target the screening test to those at high risk of developing the disease, based on considerations such as demographic factors, medical history or occupation. For example, mammograms are recommended for women over the age of forty, because that is a population with a higher prevalence of breast cancer.
Predictive value of a theoretical test at disease prevalence of 5%
Sensitivity and specificity of 90% NPV 99.4% Probability that antibodies are present when the test is negative 0.6%
PPV 32.1% Probability that antibodies are not present when the test is positive 67.9%
Sensitivity and specificity of 95% NPV 99.7% Probability that antibodies are present when the test is negative 0.3%
PPV 50.0% Probability that antibodies are not present when the test is positive 50.0%
Sensitivity and specificity of 99% NPV 99.9% Probability that antibodies are present when the test is negative 0.1%
PPV 83.9% Probability that antibodies are not present when the test is positive
Can somebody help me find the current regulations/mandates/whatever that are in place from the government? Quarantine rules, mask-wearing in certain locations, etc.
Any places. There are things the government has said/put into place, and I want to find them. Ideally a page that is updated when those regulations are changed/updated.
(edit: I see you have now)