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Sabina Vohra-Miller Profile picture
@SabiVM
May 8 • 7 tweets • 3 min read • Read on X
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New post on Rapid Antigen Tests. Will post the entire thread here instead of just a link, given importance.

A master thread with current data: key concepts, which brands are more sensitive, tips to improve sensitivity & important considerations. 1/7 RAPID ANTIGEN TESTS A master thread with current data: key concepts, which brands are more sensitive, tips to improve sensitivity and important considerations.
Recent CDC MMRW Report found overall sensitivity of RATs was 47% compared to PCR.
The peak percentage of positive RAT was 59.0% occurred 3 days after onset of symptoms.
Highest on days when fever was reported, lowest on days when no symptoms were reported. 2/7 RAPID ANTIGEN TESTS - OVERALL SENSITIVITY Recent CDC MMRW Report assessed the performance of Rapid Antigen Tests (RATs) compared to PCR. The study collected data from a household transmission study between Nov 2022 - May 2023. Overall sensitivity of RATs was 47% compared to PCR. The peak percentage of positive RAT was 59.0% and PCR was 83.0%, which occurred 3 days after onset of symptoms. Highest sensitivity for RATs was on days when fever was reported, and the lowest sensitivity was on days when no symptoms were reported.
Overall QuickVue and Flowflex had the highest sensitivity. Special mention for Australian Fanttest. Several commonly used RATs performed extremely poorly.
3/7 CERTAIN BRANDS ARE MORE SENSITIVE Several studies on Omicron-related variants have been conducted to assess the sensitivity of various brands of RATs Overall QuickVue and Flowflex had the highest sensitivity. Special mention for Australian Fanttest. A new study just published looked at 10 commonly found RATs in Canada. Of these, the three that were best performing wer that were best performing were: BTNX Cassette (spit) Flowflex Medsup The worst performers were: BTNX, PCL, PanBio, SDBiosensor, StandardO A US-based study looking at common US tests found the following sensitivity: Health 73...
One study showed RAT accuracy increased from 38% to 92% with repeat testing.
A single negative RAT test cannot rule out infection.
Current guidance suggests to repeat the test 48 hours after the first negative test & potentially a 3rd time if you still have symptoms. 4/7 TESTING MORE OFTEN IMPROVES ACCURACY Studies show that repeated rapid antigen tests increase accuracy drastically One study showed RAT accuracy increased from 38% to 92% with repeat testing. A single negative RAT test cannot rule out infection. Current guidance suggests to repeat the test 48 hours after the first negative test and potentially a third time 48 hours after the second test if you still have symptoms.
Including an oral sample along with a nasal sample on the same swab can increase test sensitivity.
5/7 ORAL AND NASAL TOGETHER CAN IMPROVE SENSITIVITY Including an oral sample along with a nasal sample on the same swab can increase test sensitivity. To do this: 1- Do not eat or drink for at least 30 minutes before collecting the oral sample. 2- Insert the swab between both inner mouth cheeks and lower gums and turn the swab around a few times. 3- Then rub the swab on your tongue as far back in your throat. You can also swab the back of your throat and tonsils. 4- Then using the same swab, insert it straight back into your nose and rotate the swab for a few seconds. Repeat in the second nostr...
If you are elderly, at higher risk, eligible for anti-virals such as Paxlovid, PCR tests are recommended.
If your RAT is positive, you continue to be infectious.
To know when to stop isolating or masking, two consecutive -ve RATs 24 hours apart (after a +ve RAT). 6/7 GENERAL CONSIDERATIONS If you are elderly, immunocompromised or at higher risk for severe disease, or eligible for anti-virals such as Paxlovid: PCR tests are recommended for you so that it doesn't delay you obtaining appropriate care and treatment. However, PCRs tests are getting harder to find and more inaccessible, which is frustrating. If your RAT is positive, you continue to be infectious. PCR tests can remain positive for up to 3 months after an infection, since they pick up all viral remnants, including dead and inactive virus and also involves an amplification step to make it more s...
A post on key concepts and considerations 7/7 Key concepts on COVID-19 Rapid Antigen Tests (RATs) RATs are an important tool; however, PCR tests are the gold-standard RATs offer a snapshot of at a specific time and place Think of it like a polaroid picture. It only offers a glimpse of what the situation is at that current time. Do a RAT just before attending an event If you're attending a family gathering in the evening, consider doing a RAT in the morning, and then another one just before you leave the house to attend the gathering. If your RAT is positive, does it mean you are infectious? YES! RATs only test for active viral nuc...

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More from @SabiVM

Sabina Vohra-Miller Profile picture
May 9
So much disinformation on AstraZeneca's announcement re: withdrawing their COVID-19 vaccine, so I thought I should go back and review the timelines of what occurred in Canada.

Hang on, because this is going to be a wild ride. Thread, and a long one. /1
theguardian.com/business/artic…
Image
AstraZeneca's COVID-19 vaccine was first approved in Canada on Feb. 26, 2021. /2
cbc.ca/news/politics/…
Image
In Canada, it was first only recommended to be used in adults 64 and younger. This is because the initial study results were too limited to allow a reliable estimate of vaccine efficacy in individuals 65+. /3
ctvnews.ca/health/coronav…
Image
Read 24 tweets
Sabina Vohra-Miller Profile picture
Apr 25
Avian Flu:
Current situation, context and what you need to know 1/8 Image
AVIAN FLU - A BRIEF HISTORY:
Highly Pathogenic Avian Influenza (HPAI) is caused by Influenza A H5 and H7 viruses. The current highly infectious strain of Avian Influenza that is spreading is the H5N1.
H5N1 is not new. 2/8 AVIAN FLU - A BRIEF HISTORY: Highly Pathogenic Avian Influenza (HPAI) is caused by Influenza A H5 and H7 viruses. The current highly infectious strain of Avian Influenza that is spreading is the H5N1. H5N1 is not new. It was first detected in chickens in Scotland in 1959; however that strain was very different from the current version of H5N1 which underwent a significant evolution around 1997. Sporadic cases and outbreaks have resulted in hundreds of human cases of the H5 Avian influenza virus, particularly the H5N1 subtype and predominantly from direct contact with infected birds in comme...
Currently we have an outbreak of the subtype H5N1 clade 2.3.4.4b.
There are 33 outbreaks across 8 states in cattle reported in USA. None in dairy cattle in Canada, CFIA monitoring closely.
This degree of spread outside of birds & poultry is unprecedented & concerning.
3/8 Currently we have an outbreak of the subtype H5N1 clade 2.3.4.4b. There is some data to show that this strain requires a lot more direct contact for spread to humans than H7N9. Avian flu has been spreading amongst wild birds, poultry and as of recently, dairy cattle. It is now estimated that it has been spreading in dairy cattle since late 2023. As of April 21st, there are 33 outbreaks across 8 states in cattle reported in the USA alone. Avian flu has not yet been discovered in dairy cattle or other livestock in Canada; however, CFIA is currently on high-alert and monitoring closely. In add...
Read 10 tweets
Sabina Vohra-Miller Profile picture
Apr 2
In science & esp medicine, risk is a tricky thing to contend with - besides of course being a mathematical one - and involves many considerations in order to have a more fulsome understanding.

In this post @LizMarnik and I attempt to explain these concepts. 1/9 Let’s talk risk What is relative vs absolute risk? What is cumulative risk? Why do these terms matter? And how do these impact our lives?
In simple terms, risk is the probability of an event occurring. In statistical terms, the risk of an event occurring is simply defined as its probability.
2/9 WHAT IS RISK? In simple terms, risk is the probability of an event occurring. In statistical terms, the risk of an event occurring is simply defined as its probability. Absolute risk of a disease is your risk of developing the disease over a time period. Relative risk is used to compare the risk in two different groups of people. What does this mean?
Take a fictitious disease - AhCrap. Risk of dying due to this is 2/million & using GoodStuff tx can reduce risk to 1/million.
While relative risk reduction is 50%, only one less person out of 1M w AhCrap are saved by GoodStuff, making absolute risk reduction fairly small.
3/9 ABSOLUTE VS RELATIVE RISK Take a fictitious disease, say Disease AhCrap. The risk of dying due to AhCrap is two in a million - ie, for every one million people who suffer from AhCrap and are not treated, two out of these one million people will die. Let's say we have a way to treat this AhCrap disease, using GoodStuff treatment. This treatment can reduce the risk of dying from two in a million to one in a million. Because the risk of dying decreased from two in a million to one in a million, the relative risk decreased by 50%. However, the absolute risk only changed from 2/1,000,000 to 1/1,...
Read 9 tweets
Sabina Vohra-Miller Profile picture
Feb 26
A week ago, a new paper was published evaluating the safety of Pfizer, Moderna & AstraZeneca vaccines. Unfortunately, the media’s response with sensational headlines has been both irresponsible & misleading.

Here is a deep dive I did with @LizMarnik & @niniandthebrain

🧵 1/10 COVID VACCINE SAFETY Benefits outweigh risks
Study in question:

2/10 sciencedirect.com/science/articl…
Article https://www.sciencedirect.com/science/article/pii/S0264410X24001270
This study evaluated the rate of several rare events in the 42 days post vaccination compared to pre-COVID rates

The study looked at 99,068,901 individuals that represented over 242 million doses of Pfizer, Moderna or AstraZeneca.
3/10 RARE ADVERSE EVENTS EVALUATED This study evaluated the rate of the following events in the 42 days post vaccination compared to pre-COVID rates: : Guille dissemisated ence/caloyelitis (ADEM) • Transverse myelitis (T™) • Bell's Palsy. • Febrile and generalized seizures • Cerebral venous sinus thrombosis (CVST) • Thrombocytopenia • Pulmonary embolism (PE) • Splanchnic vein thrombosis (sVT) • Myocarditis • Pericarditis The study looked at 99,068,901 individuals that represented over 242 million doses of Pfizer, Moderna or AstraZeneca. @Niniandthebrain x @UnambiguousScience x @ScienceWhizLiz
Read 10 tweets
Sabina Vohra-Miller Profile picture
Jan 21
Does Long Covid alter the immune system?

New evidence suggests this may indeed be the case.

Study summary in collaboration with @LizMarnik
1/7 Image
This is the study we attempt to summarize:


2/7 nature.com/articles/s4159…
Research is slowly starting to find out what processes may be behind some of the symptoms those with long COVID experience. Image shows screenshot of actual article
Samples were collected via a prospective observational study that enrolled individuals with prior SARS-CoV-2 infection with and without long COVID symptoms
3/7 Participants were enrolled in a prospective observational study that enrolled individuals with prior SARS-CoV-2 infection with and without long COVID symptoms. Samples were collected from participants at 8 months post infection before any participants were vaccinated or reinfected. Results were compared between those with long COVID symptoms to those without.
Read 7 tweets
Sabina Vohra-Miller Profile picture
Aug 23, 2023
A few months ago this year I was lucky to be included in the taping of a fairly big TV show as an extra.

The number of Covid-related safety precautions they took throughout the entire taping was incredible:
🧵
First, I needed to get a same day PCR test done.

An entire dedicated testing team that was completely outdoors was set up just for the acting crew.

The results were sent directly to the manager handling extras. You were not allowed inside until they received the results.
Then I was asked to wear a mask when we were not actively shooting a scene.

This meant wearing the mask back on sometimes just for 30s in between shots. Management crew would come up to actors to ask them to mask if they forgot. The main actors didn’t have to mask (makeup etc)!
Read 5 tweets

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