Is it more likely to get false negative or false positive?

My understanding is false negative is more likely to occur.

That is correct. It is not as sensitive as PCR.

However, someone posted some data on another thread about a Sofia Antigen test showing very sensitive test, meaning very low chance of a false negative. If those numbers hold up on a larger scale, that would be huge.

We just started doing antigen testing, but send for PCR if the antigen is negative.

I took my daughter to get a rapid antigen test yesterday and the lab tech told me that the rapid test they use is very accurate and they are more likely to get false positives. Hopefully she didn't just tell me that to feel better about it, but that's what she said. We went to a urgent care called Virtual Care for Families in the Woodlands. My daughter's test was negative.

As a company we no longer rely on rapid tests, either antibody or antigen, for return to work due to high rate of false negatives.

We still have at risk employees complete rapid tests, but only to see if positive so that the employee and the company can take prompt action to further contain the spread and seek additional medical care if needed.

As antedotal evidence, we had an infection event where upto 26 employees may have been exposed over the course of 5 to 7 days. FYI, this period of time after exposure is considered to greatly improve the accuracy of the rapid anti-body test. All 26 had both a rapid anti-body test and PCR test specimen collected on the same day. All 26 rapid tests were negative. 5 of the 26 PCR tests came back positive. 3 of the 5 COVID positive individuals developed symptoms and recovered while waiting for the PCR test results that took 8 days to receive.

To date we are still continuing to do rapid tests, but still require employees to self isolate according to CDC guidelines or until a negative PCR test result is returned, whichever occurs first.

A rapid anti-body test will likely be negative for 2-3 weeks post infection, depending on the type of antibody being tested for and the test sensitivity.

A rapid antigen test should have a detection window starting about 5-7 days post exposure, with the sweet spot likely at the 7-9 day mark.

Are you all relying on rapid antibody or antigen test for quick contact tracting measures? Can't tell if you mean't antigen when you wrote antibody.

Interesting theory in this med-cram video about rapid testing. From what I can understand from the video, even though the rapid testing may not be as sensitive, it should pick up folks who are contagious. So, is it better to do more of the rapid testing, because if you are doing it daily you will eventually pick up the contagious folks and have them stay home from work/school or use a more sensitive test that takes days or weeks to get the results back?

The medcram videom makes sense. Seems like we should transition to the rapid test which could identify folks that are actually contagious. Not the folks who have a small remaining viral load and pop positive on the PCR test who don't pose a threat of passing it on. Seems too logical so I am sure this won't become common practice.

San Antonio was including rapid testing as probable COVIDs in their numbers and were asked to not do so by Texas Dept of Health. So San Antonio is having to go back and separate those numbers out.

Of course the headlines make it sound like San Antonio was artificially inflating the numbers with untested people they just called "probably COVID," vice actual tested people with positive antigen tests that aren't as sn/sp as PCR.

So if someone wants to believe that local officials are pumping up the number, they'll just read the headline and form their opinion without educating themselves on what an antigen test is. This'll likely push health officials to rely on PCR more to show the true extent, and disincentivize the use of antigen testing. Maybe.

But I agree that antigen should be rolled out. Positives should be counted as positive, and negatives can get sent for back up PCR if there's sufficient concern and it'll change management.

https://www.sanantonio.gov/gpa/News/ArtMID/24373/ArticleID/19185/San-Antonio-Metro-Health-separates-%E2%80%9Cconfirmed%E2%80%9D-COVID-19-cases-from-%E2%80%9Cprobable%E2%80%9D-cases-at-the-request-of-the-state

https://www.kens5.com/article/news/health/coronavirus/san-antonio-health-officials-clarify-confusion-over-reporting-probable-coronavirus-cases-in-bexar-county/273-7d8b9d8e-8255-4d03-8db0-deb28a3c8348

https://patch.com/texas/sanantonio/san-antonio-metro-health-separates-confirmed-coronavirus-cases-probable-cases

So after posting the MedCram video I was thinking about school districts here in Dallas. I heard that Garland spent something like 4 million bucks on protective equipment for the kids and teachers. I'm thinking, why not spend a fourth of that on tests for every kid in the district, and then if they test positive, stay home from school. Seems like that could work, right?

czechy91 said:

---

The medcram videom makes sense. Seems like we should transition to the rapid test which could identify folks that are actually contagious. Not the folks who have a small remaining viral load and pop positive on the PCR test who don't pose a threat of passing it on. Seems too logical so I am sure this won't become common practice.

---

just watched it and agree completely. One question I have is: Does everyone that have COVID at some point reach that ct value of 30 or less (higher viral load)? Or is it possible they just never reach that viral load (probably have very mild symptoms or no symptoms)?