Childhood
Nostalgia is a small stamp
Grow up
Nostalgia is a nucleic acid test report that says "negative."
(Image source: Internet)
Our lives are once again shrouded in the shadow of the epidemic
When going out, it is as important as the ID card -
There was also a negative nucleic acid test report
Are you curious:
From the time you arrive at the site of the nucleic acid test
And then --
Look up
Let a cotton swab poke into your throat & nostrils
(Image source: Internet)
What happened in the ten hours between getting the nucleic acid test report?
What happened to your throat/nasal swab specimen that was taken? How exactly did your nucleic acid report come about?
Today, we have a full disclosure.
Everything starts long before you go downstairs to test.
First of all, in the selection of temporary sampling rooms, the following series of work has been done to ensure safety and accuracy, so as not to "set up a stall" on the side of the road.
Next, there's sampling.
For you, you just have to
"Open your mouth—"
"Head up a little—"
Why does a cotton swab either poke the nostrils or the throat?
The nasal cavity and throat area are the only way for respiratory secretions to be discharged, so the presence of the new crown virus can be most detected here.
The new crown pneumonia virus is transmitted through droplets or aerosols, mainly infecting the respiratory system of the host, the virus colonizes the respiratory tract and multiplies rapidly, and the virus population increases sharply and is detoxified outward through respiratory secretions.
The nose poke detects the nasopharynx, and the poke throat detects the oropharynx, and their positions are relatively deep, and there is no difference in nature.
In order to ensure accurate sampling, laboratory personnel need to ensure the standardization of specimen collection.
Whether it is a nasopharyngeal swab or an oropharyngeal swab, there are certain requirements for the depth of collection.
So, when you spit on being poked in the throat so crazy that your throat grows a cocoon —
(Image source: Internet)
It's not that the staff has a vendetta against you.
If it is a nasopharyngeal swab sampling, the key point of sampling is: "To be deep, to turn, to take the cells." ”[2]
"To be deep" is to go deep from half the length of the earlobe to the tip of the nose
"To turn" is to turn 10 to 15 seconds, about 4 to 5 turns
"To take cells" is to take cells from the nasopharynx
(Image source: References[2])
If it is an oropharyngeal swab, it is also necessary to wipe the bilateral pharyngeal tonsils and the posterior pharyngeal wall 3 to 5 times with a swab.
After lisodil sampling, the swab head is immersed in a tube containing 3 ml of viral preservation solution (also using isotonic salt solution, tissue culture solution, cell preservation solution, or phosphate buffer), the tail is discarded, and the lid of the tube is tightened [2].
In this way, your throat/nasal swab sample will be stored in an airtight container.
Image source: Stand Cool Helo
The new crown virus is highly contagious, so the nucleic acid testing staff should also be fully armed to ensure safety.
When the sample is collected and before entering the laboratory, it is necessary to use secondary protection before entering, that is, wearing disposable protective clothing, wearing goggles or face shields, wearing double gloves, wearing N95 and above masks, hats and protective boot covers, etc., so most of the staff you see doing nucleic acid testing are fully armed.
Heavy protection isolates the virus, but it is also thick and heavy. Even "cool in winter and hot in summer". Therefore, in the cold and hot weather of the test, the staff will need a strong will even more. (The "Great Whites" are hard!) Thank you! ）
(Image source: Chinese government website.) On August 4, 2021, at the community sampling point of Shuanghe Road, Shuangfu Street, Jiangjin District, Chongqing, Zhao Qingyong, a medical staff of the Third People's Hospital of Jiangjin District, completed two rounds of sampling work and took off his protective clothing and went upstairs [3]. ）
The staff wearing secondary protective equipment will also spray the outside of the sealed bag with 75% alcohol or effective chlorine disinfectant to prevent the surface of the test tube from carrying the virus, and then store it in a special sample transfer box, and after layers of packaging, it will be transported to the testing laboratory by a special vehicle.
Samples are not tested immediately after being escorted to the laboratory. The staff will open the package one by one and enter the information of each specimen into the system, as if to account for each sample.
After entry, each sample has its own exclusive identity on the network, after which its test results will be firmly bound to your health code situation.
Finally, the critical stage of sample processing and testing has arrived.
Image source: Stand Cool Helo
You may have wondered how scientists know if you have a virus in your body?
To answer this question, we must first understand a professional detection technology, nucleic acid amplification technology, which can detect the presence of specific gene fragments in a sample. At present, the kits approved for marketing in mainland China are also mainly based on nucleic acid amplification technology.
You who have not returned all your high school knowledge to the teacher may remember.
Each sample must be tested for the nucleic acid of the new crown virus, and the nucleic acid needs to be extracted first, which is commonly referred to as a template. After the template and the assay reagent are mixed in a certain proportion, it is ready for on-board testing.
In the reaction tube, the primers contained in the reagent bind to a specific gene sequence of the new crown nucleic acid and continuously replicate new nucleic acid fragments under the action of enzymes. Each round of the reaction causes a specific nucleic acid fragment to be copied once, and the number increases exponentially. Each time a particular gene is copied, a fluorescent signal is released.
If a specific gene fragment does exist in a sample, a specific fluorescent signal is emitted.
At present, the site targeted by the nucleic acid detection of the new crown virus mainly contains three conserved gene sequences in the virus genome, that is, the open reading frame 1ab (ORF1ab), the nuclear shell protein (N) gene and the envelope protein (E) gene as the detection target.
If there is no significant change in the fluorescence signal, then congratulations – there is a high probability that it is safe [4].
(Image source: References[4])
Not necessarily, though.
This is because there is a possibility of false negative nucleic acid tests for the new crown virus. A negative result cannot exclude covid-19 infection, and the causes of false negatives in each link should be considered.
The nasopharyngeal swab or throat swab specimen currently used is mainly detected using the qPCR kit, which has only a positive detection rate of 30% to 50%. In order to ensure the rapid screening of large-scale personnel, under the current technology, this false negative result cannot be avoided, so in the epidemic area, the quarantined person often needs to undergo nucleic acid testing multiple times [2].
That is, being poked in the throat/nose seven or eight times a day. (You guys worked hard)
A negative test is not necessarily true that there is no infection, and if the test result is positive, it is tense.
When the mixed test is carried out, it can only be judged that there may be positive specimens in this batch of samples, and then the people who are mixed with the test will be subjected to another nasal/throat swab-nucleic acid test to determine who the positive infected person is.
In order to prevent possible contamination, the tested samples are also placed in designated medical garbage cans for high-pressure destruction.
Congratulations, yin.
Finally, we came to the closing stage.
The staff will check the information one by one and upload the test results to the system. It is this step that allows you to easily find the results on the Internet.
"Negative" – will be the two most pleasing words.
(Image source: Internet)
However, it should be noted that the new crown virus will continue to replace the state in the human body, and if it is sampled during the suppression period, it cannot be detected.
If you drink water, smoke, drink alcohol, etc. before sampling, it may also interfere with the test results.
Therefore, even if it is a negative result, everyone must wear a mask at all times when going out, which is responsible for both themselves and others!
(Image source: Internet)
Recently, many people are sighing, but they did not expect that it has been more than 2 years, and the epidemic is still affecting our lives.
Always do a good job of self-protection, actively vaccinate (remember to do it if you have not yet received a booster injection), and constantly improve our anti-virus ability is the right solution.
bibliography
[1] Su Zhenjiao, He Jinwen, et al. Evaluation of Nursing Quality Control in the Whole Process of Novel Coronavirus Specimen Collection[J], Journal of Gannan Medical College, 2021,41(11):1101-1105.
Tong Yongqing, Wang Ming, Xu Wanzhou, et al. Recommendations on Clinical Laboratory Practices for Nucleic Acid Detection of Novel Coronavirus [J] . Chinese Journal of Laboratory Medicine, 2020, 43(3): 209-212.
[3]http://www.gov.cn/xinwen/2021-08/04/content_5629435.htm#8
[4] An article to understand the nucleic acid detection of the new coronavirus [EB/OL].http://yjj.beijing.gov.cn/yjj/xxcx/kpxc/ylqx6/1714959/index.html
Author: Zhang Xiaoyi, Jiang Yongyuan
*The content of this article is a popularization of health knowledge and cannot be used as a specific diagnosis and treatment recommendation, nor is it a substitute for face-to-face consultation by a practicing physician, for reference only.
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