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8

The first case of covid-19 was thought to have been diagnosed on the 17th November 2019 involving a 55 year old resident of Wuhan with viral pneumonia. With a R0 of 2.5 they would have already infected at least 2.5 other persons but for simplicity's sake let's say that on 17th November, 2019 there were 2 cases including the person diagnosed. At that time ...


6

A chest X-ray can detect changes in the lungs that occur in certain infections, such as pneumonia, tuberculosis, tularemia, aspergillosis, histoplasmosis, plague, etc (American Journal of Rentgenology). In most cases, additional tests, such as sputum and blood tests, are needed to confirm an exact diagnosis. Here and here you can see which other lung ...


6

This page from the NIH has a lot of relevant information about lactose intolerance. There are several standard diagnostic tests for lactose intolerance, but your physician might ask you to try eliminating dairy from your diet before you receive any of those tests. If avoiding lactose alleviates your symptoms, you've potentially treated your primary lactose ...


5

According to Healthline the skin sould bounce back within a second or two. The pertinent passage is: When you pinch the skin on your arm, for example, it should spring back into place with [sic] a second or two. The article also mentions that this should be done on your arm or abdomen. MedlinePlus says the same. This is called skin turgor. It is not ...


5

There's yet another reason: a test can provide only a certain amount of information gain. If the probability to have contracted Covid-19 before the test is too low, even though we know more after the test we may not be able to draw practical conclusions that are any different from the recommendations without test. In other words, if the recommendation goes ...


5

Update Apr 2: Pooled tests are under development now (newspaper in German), the plan is to pool 5 samples and to use the usual amount of each sample (and presumably dilute less) so that sensitivity is not an issue. Update Apr 9 NYT article mentioning a pooled procedure for routine tests for health care workers (pooling 10 samples) in Germany. In general, ...


4

China has been using antibody testing to see if people had been exposed in their convalescent phase. The USA didn't want to do antibody testing and have wanted to recover virus using a PCR test, but PCR won't show historical infection. Open source antibody tests have been described but presumably will need to wait for FDA/CDC approval ( https://www....


4

CDC guidelines for when patients should be tested have changed since the ones you list. CDC now says: Clinicians should use their judgment to determine if a patient has signs and symptoms compatible with COVID-19 and whether the patient should be tested. Most patients with confirmed COVID-19 have developed fever1 and/or symptoms of acute respiratory illness ...


4

You are searching for the false-negative rate of these tests. A test resulting in a negative outcome while it should have been a positive outcome. A recent article stated that most of the false-negatives of COVID-19 tests are actually caused by not properly taking the samples from nose and throat. While I cannot find the original article I've got this ...


4

The ratio of false positives to true positives (as well as overall "accuracy") is a function of the underlying rate in the population. Let's imagine you have a test that has 95% specificity. Specificity is the number of negatives that you correctly identify as negative. If you test 1000 negative samples with a 95% specificity test, you will find 95%...


3

It's because influenza attacks ciliated cells, and you get the best specimens where you include cellular material Acceptable respiratory specimens Most tests can be used on a variety of respiratory specimen types, however not all specimen types yield equivalent results, and other factors can influence specimen quality. Nasal aspirates, nasal ...


3

University of Washington (UW Medicine) suggests Testing Criteria on their site: https://covid-19.uwmedicine.org/Pages/default.aspx The following patients with COVID-19 symptoms should be tested for COVID-19: • Patients hospitalized with severe lower respiratory illness • Healthcare workers • Patients in other public safety occupations (e.g., law enforcement,...


3

South Korea has adopted a highly technical and transparent approach to Covid-19. By sharing where infected people have been, citizens can see if they have been in contact or near contact with the infected person, and then request a test. Since the first cases were confirmed, Korean public health authorities and local governments collaborated to precisely ...


3

There are two general categories of tests typically used for identifying viral infections: those based on viral genetic material and those based on host immune response. The CDC page on MERS-CoV testing (also a coronavirus, just not the one that causes COVID-19) is an informative resource to start with (bold added and reformatted by me): Molecular tests are ...


3

When you're doing a nasopharyngeal swab you want primarily cellular material that is infected with virus. You can cut the tip of the swab successfully as in this study for multiple tests Study design We collected a NP swab on children aged 2–12 years with acute sinusitis and processed it for bacterial culture, viruses, cytokine expression, and 16S ...


3

The principal goal of pooled testing is to rapidly clear many cases in low prevalence (or incidence) situations. Long version: Disclaimer: I'm analytical chemist, i.e. someone who could by profession be involved in developing such tests, but I'm not involved in SARS-CoV2 testing or SARS-CoV2 test development. What I write here is basically my general ...


3

Multiple tests can decrease the chance of a false negative. The probability of detection varies with the time since exposure. This Nature article presents an informative (albeit rough) graph. Suppose, for example, your Saturday and Thursday tests occurred at the times I labeled on the graph below: Then it would be quite possible for the Saturday test to ...


3

I have found on the internet (see sources below) that the answer is in general no, for two reasons: the serological test must detect the antibodies related to the Spike protein, and this condition is not respected by most of rapid tests. In particular, some look for the nucleocapside protein which is contained inside the virus (not on its corona like the ...


2

Tests that one may want to do annually: Blood pressure; increased BP is a risk factor for heart disease Checking your skin for moles, which can develop into cancer Blood cholesterol and triglycerides (lipid profile); increased levels are risk factors for coronary heart disease Blood glucose to check for diabetes mellitus Dental check for caries Eye ...


2

Those test results indicate a positive result for traces of Helicobacter pylori in the sample given. No-one on here will give you any more medical advice. Go see your doctor with those results.


2

I am working in the information security industry and personally following medical technology closely. Your first question kind of asks to predict the future, which nobody can. Yet, I will give you my personal opinion on the matter. Is it reasonable to expect the cost of sequencing an individual's genome to drop so much in the near future as to allow for ...


2

The claim that "water is not close to an optimal hydration solution because it goes right through you into the urine" is grossly exaggerated. Water is just good for hydration; even if somewhat more effective beverages are available, they are not really necessary for everyday needs. Sugars speed up water absorption. Fructose stimulated 66-100 per ...


2

I cannot answer about South Korea, but as far as other drive-in test stations are concerned the rules I've seen are: Call ahead to get checked whether testing is indicated, get issued a special testing number. Go there, get tested with the testing number. Go back home, get test result via mail.


2

First of all the disclaimer: I'm analytical chemist but not clinical chemist. That is, I professionally do things that are related/to some extent similar to test kit development, but not for medical use, and I've only been very remotely involved with microbiology-related testing. OTOH, I expect that pretty much everyone who works in this field is likely to ...


2

Is SK conducting random covid-19 tests on sizeable random samples of its population? Not currently (source: South Korean friends). Is any other country with a major outbreak doing such a thing? See Why don't we take a random sample of the population to estimate the amount of COVID-19 cases?


2

Why is surveillance not implemented at scale in the USA? Not enough test kits. If the USA does not have testing at scale, why is this the case? Didn't go through MERS and SARS, unlike South Korea. E.g see https://www.theguardian.com/world/2020/mar/15/experience-of-sars-key-factor-in-response-to-coronavirus


2

The results are probably in the Chinese press, but are being reported elsewhere China has reported 51 new coronavirus cases including 40 asymptomatic infections, majority of them in the contagion’s first epicentre Wuhan, where over six million tests have been conducted in the last 10 days, health officials said on Monday. So, looks like large scale ...


2

From Time: June 3, 2020 Wuhan Tests Nearly 10 Million People in 19 Days, Finding Just 300 Coronavirus Infections (BEIJING) — The Chinese city of Wuhan, where the coronavirus was first detected late last year, has tested nearly 10 million people in an unprecedented 19-day campaign to check an entire city. It identified just 300 positive cases, ...


2

There are several use cases. But the main reason is always to operate in a situation where the number of tests is a bottleneck or constraint. In the USA, this is usually because of limited test reagents or limited laboratory techs and machines to run the PCR. If you have unlimited testing, you would not use pooled testing. One use case is surveillance. You ...


1

This calculator suggests that the antibody tests aren't too bad in that they're suggesting that the official figures are way too low. https://gabgoh.github.io/COVID/index.html The first death in California was on the 6th Feb 2020 which means the disease was likely introduced in mid-January 2020. Assume a case fatality ratio of 0.014 (In NZ We have had ...


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