15 votes
Accepted

Rapid Response COVID-19 Antigen Test: What can be assumed by the control bar?

Your explanation numbered 1 is correct. The control line indicates that the antibodies required to detect the SARS-CoV-2 (the virus that causes COVID-19) particles have reached that location on the ...
Ian Campbell's user avatar
  • 3,256
9 votes
Accepted

Can a RT-PCR test claim 100% sensitivity and specificity?

A diagnostic test should never claim 100% sensitivity or specificity. So we are all on the same page, let's review what sensitivity and specificity actually mean. According to the US Food and Drug ...
Ian Campbell's user avatar
  • 3,256
8 votes

Why were so many Covid-19 negative tests among close contacts of the early Chinese cases?

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 ...
Graham Chiu's user avatar
  • 13.3k
6 votes
Accepted

What contagious diseases can be diagnosed by x-ray test on chest?

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)...
Jan's user avatar
  • 15.9k
6 votes
Accepted

How would I know whether I am lactose-intolerant? Are there any tests?

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 ...
Bruce Kirkpatrick's user avatar
5 votes
Accepted

Can the capacity for COVID-19 tests be amplified by testing multiple samples mixed together and testing each only if positive?

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 ...
cbeleites unhappy with SX's user avatar
5 votes
Accepted

What is the correct way to use the pinch test for dehydration?

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 ...
BillDOe's user avatar
  • 1,400
5 votes

Why are people with COVID-19 symptoms being denied tests in the US?

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 ...
cbeleites unhappy with SX's user avatar
4 votes

Why are people with COVID-19 symptoms being denied tests in the US?

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 ...
Bryan Krause's user avatar
  • 14.1k
4 votes
Accepted

Is there a way to test for covid 19 after recovery?

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 ...
Graham Chiu's user avatar
  • 13.3k
4 votes

Is it possible that COVID-19 virus exist in a human body, but be absent from samples taken from nose and back of throat?

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-...
Bob Ortiz's user avatar
  • 1,019
4 votes
Accepted

Antigen vs PCR test

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. ...
Bryan Krause's user avatar
  • 14.1k
4 votes
Accepted

Can false positives/negatives be reliably detected by redoing the test?

Although somewhat buried in the question, it appears you are interested in Brucellosis. Brucellosis is an infectious disease caused by bacteria of the Brucella genus including B. melitensis, B. ...
Ian Campbell's user avatar
  • 3,256
4 votes
Accepted

Control for glucose test strip

According to Cowart and Stachura (1990 NBK 245): Techniques for measuring glucosuria are based upon either glucose oxidase (specific for glucose) or copper sulfate reduction (nonspecific: detects ...
Ian Campbell's user avatar
  • 3,256
3 votes

What is the best protocol and criteria or policy for COVID-19 novel coronavirus testing?

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 ...
Henry Wei's user avatar
  • 638
3 votes

Is South Korea doing "random" testing to combat covid-19 epidemic?

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 ...
Graham Chiu's user avatar
  • 13.3k
3 votes

Having tested positive for COVID-19, will future tests be positive?

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 ...
Bryan Krause's user avatar
  • 14.1k
3 votes
Accepted

Why isn't saliva sampling used when sampling for the presence of respiratory diseases?

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 ...
Graham Chiu's user avatar
  • 13.3k
3 votes

COVID-19: Is it possible to use the specimen collected through swabs for multiple tests

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 ...
Graham Chiu's user avatar
  • 13.3k
3 votes

What is the principal goal in pooled COVID-19 testing?

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 ...
cbeleites unhappy with SX's user avatar
3 votes
Accepted

Do having multiple COVID tests decrease the chance of a false negative?

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, ...
unutbu's user avatar
  • 397
3 votes
Accepted

Covid19 Rapid serological tests and Vaccine

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 ...
Avles Edivad's user avatar
3 votes
Accepted

Meaning/Abbreviation of IAAD IA & IAADIADOO

These look like they are from CPT codes ("Current Procedural Terminology"; these are billing codes). They probably come with a numeric descriptor; you're looking for a "long descriptor&...
Bryan Krause's user avatar
  • 14.1k
2 votes

Lactase quantity test?

The typical way to measure enzyme concentration is via enzyme activity: if there's more of an enzyme, you'll see faster conversion of reactant to product. So actually yes, adding a known amount of ...
Bryan Krause's user avatar
  • 14.1k
2 votes

is 1.319 IU/ML Helicobacter Pylori IGG normal?

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.
John's user avatar
  • 1,104
2 votes
Accepted

What medical tests a man should take regularly to check for common health issues?

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 ...
Jan's user avatar
  • 15.9k
2 votes

Technology prospects for genome sequencing at home and data protection

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 ...
Bob Ortiz's user avatar
  • 1,019
2 votes

What is the "best" or most accurate way to measure bodily hydration?

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 ...
Jan's user avatar
  • 15.9k
2 votes
Accepted

Is there a convenient self test for Glaucoma?

Disclaimer: I have no formal medical or vision science training. Please point out any factual errors. My test is based on the idea that Glaucoma is indicated by pressure on optic nerve, which one may ...
Ruminator's user avatar
  • 601
2 votes

How do they test COVID-19 in drive-thru labs?

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 ...
Thomas's user avatar
  • 1,161

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