Recently, the comprehensive group of the joint prevention and control mechanism of the State Council decided to add antigen detection on the basis of nucleic acid detection as a supplement, and community residents who have self-testing needs can purchase antigen detection reagents for self-testing through retail pharmacies, online sales platforms and other channels.
On March 18, Liu Min, director of the Department of Medical Laboratory of the First Affiliated Hospital of Sun Yat-sen University, and Chen Peisong, MD, were interviewed by yangcheng Evening News reporters, explaining the steps of antigen self-testing and answering common questions.
【Operation steps】
Irregularities can affect accuracy
1. Wash your hands first or disinfect your hands quickly.
2. Unpacking: The antigen self-testing agent box generally contains instructions, detection cards, swabs, sample extraction solution, and sample extraction tubes. Read the instruction manual before use, there may be slight differences in different brand operations.
3. Open the sample extract first and pour it all into the sample extraction tube.
4. Open the test card package and remove the test card. Before the test results come out, it is best not to touch the test card again, so as not to pollute and affect the test results.
5. If there is more nasal endocrine, you can blow your nose before the test.
6. Take out the swab, be careful not to touch the swab head.
7, the head is raised backwards, the swab is slowly pushed along the inner wall of the nose 1-1.5 cm, until the swab head is not visible, turn 4 times, stay for 15 seconds, mainly to increase the contact surface and the amount of sampling when sampling. The same swab is then sampled in another nostril, also turned 4 times and left for 15 seconds.
8. Put the swab into the sample extraction tube, immerse the swab head into the extract, and rotate the swab for 15 seconds while squeezing.
9. Then put the swab into the original packaging bag to avoid polluting the surrounding environment.
10. Close the lid of the sample extraction tube.
11. Flip the extraction tube over and drop 3 drops of extract from the lid to the detection card. To strictly follow the instructions of the instructions of the instructions to drip, the number of drops is not enough, the number of drops is too much, may cause "false negative".
12, generally in 10 to 15 minutes can judge the result (different brands have differences).
Red bands (i.e., "two bars") are positive at both C and T.
The red band displayed at C is negative (i.e. "a bar").
If the red band does not appear at C, it indicates that the detection is invalid and needs to be retested.
After 13 or 30 minutes, the result will be invalid (different brands vary).
【Frequently Asked Questions】
1. Suspect that you have been to a "dangerous" place, and you should be tested within a few days to be more accurate?
A: If you suspect you've been exposed to COVID-19, it's best to get tested within 5 days. At present, the new crown virus is characterized by a relatively fast onset, a relatively short incubation period, in the 5 days of infection of the virus copy number will be relatively high, and then the copy number will begin to decline, more than 5 days later with antigen self-test box may appear missed diagnosis, it is recommended to directly carry out nucleic acid testing.
2. Allergic rhinitis is often washed with sea salt water, can the nose be washed before testing?
A: No, you can't. Because the virus is attached to the nasal mucosa, washing the nasal cavity with normal saline will reduce the concentration of the virus and affect the sensitivity of the test.
3. If you can't get your hands on it, can you ask your friends and relatives to help "pick it up"?
A: Children under the age of 14 should be sampled by their parents. Adults recommend taking their own samples, compared with others, they are more aware of their feelings, easier to grasp the strength, and the sense of comfort is stronger.
4. What should I do if the test result is positive?
A: If the self-test result is positive, it should be reported to the community (village or town) immediately, and the community (village) should contact the emergency center and transfer the residents to the medical institution set up by the fever clinic for nucleic acid testing in accordance with the guidelines for the transfer of personnel related to the new crown pneumonia epidemic.
5. Why is the test result "invalid"?
A: It may be that there is a problem with the preservation of the kit, or the temperature of the detection environment does not reach the specified range, or the amount of liquid added by drops is insufficient, or the design process itself may cause the test result to be "invalid", that is, the red band is not displayed at C.
6. What are the circumstances and who will test for "false positives"?
A: Taking the kit we just used as an example, its sensitivity, that is, the specificity of the test is about 95% to 97%, which means that there will be a false positive of 5% to 3%, and if 100 people use it for testing, 3 people may have false positives.
There are many cases that cause false positives, because antigen detection is essentially to detect antigen antibody responses, and some components of our human body may cross-react with the detected antibodies and lead to false positives. According to our usual experience of antigen testing, patients with autoimmune diseases are prone to false positive results. In addition, if the human body is infected with a virus similar to the new crown virus, it may also have a cross-reaction, resulting in false positives.
7. How to deal with the swab and test box after the test?
A: If the result is negative, it can be put into a sealed bag and treated as ordinary household garbage. However, if it is a specimen of an isolated observer, even if the negative result is negative, it must be handed over to a special person for disposal as infectious medical waste. If the result is positive, the subject can be taken away when they are transported or handed over to environmental killers for handling.
8. The test results have failed after tens of minutes, so how to retain the test results?
A: You can take a photo to retain the results as soon as the test results come out.
9, online shopping a box has 20 copies, how to save the unused, do you need to put it in the refrigerator for refrigeration?
A: The preservation temperature of the antigen self-testing agent box is 14-30 ° C, which can be stored at room temperature in the current season.
10. Is the test card "safe" if it is "a bar"?
A: Not necessarily, to use the antigen detection kit to detect the new crown virus also need to have several conditions: one is to obtain a good material; the second is that the viral load should reach a certain threshold, if it is below the detection limit, there will be a missed inspection; third, in the operation process, it is necessary to strictly follow the instructions.
【Journalist Experience】
Acceptance is high, but people with a sensitive nose will feel sour
The reporter brought 4 antigen detection kits back to Yangcheng Evening News, one for self-testing, and invited three colleagues to experience. The experience of the reporter himself is that when the swab is placed in the nasal cavity, it is best to put a mirror in front of it, otherwise it may not reach out. When the swab is extended into the nasal cavity and rotated in a circle, it feels much better than the previous nucleic acid nasopharyngeal swab examination of "directly poking from the nose to the brain plasma", but it is still more "sour".
The feedback from one colleague was that it was easy to operate, without any discomfort, and completely acceptable. The other two colleagues have different degrees of nasal sensitivity, when the swab into the nasal cavity will feel uncomfortable, and there will be nose itching, want to sneeze feeling, one of the colleagues with severe allergic rhinitis, the discomfort is also the greatest. But they all said that compared with nucleic acids, the comfort is still much higher, completely within the acceptable range, and from the economic cost and time cost considerations, the antigen self-test is much more cost-effective.
【Purchase Guide】
How to choose an antigen test box? Preference is given to nasal swabs with high sensitivity and sampling
The reporter noted that Taobao, Jingdong and other e-commerce platforms have been listed on the new crown antigen self-test kit, and the sales of some products have grown rapidly.
According to the official website of the State Food and Drug Administration, as of March 17, the State Food and Drug Administration has approved 14 new coronavirus antigen detection reagent products. Manufacturers include Guangzhou Wanfu Biological, Beijing Jinwolf, Shenzhen Huada Inyuan, Beijing Heatscape Biology, Beijing Lepu Diagnostics, Beijing Wantai Biological, etc.
It is understood that the new crown antigen self-testing agent box mainly uses colloidal gold method, latex method, fluorescent immunochromatography method and magnetic particle chemiluminescence method, etc., and the sampling methods include nasal swab, throat swab and nasopharyngeal swab.
Liu Min introduced that the sensitivity of the common antigen self-test kit on the market is 75%-98%, and the kit with higher accuracy is selected as much as possible under the condition. As for the sampling method, Chen Peisong recommends the use of nasal swabs, this sampling method generally extends into the nasal cavity more than 1.5 cm, but still in the nasal vestibular, ordinary people can operate, if the nasopharyngeal swab needs to reach the depths of the nose, at least four or five centimeters, will reach the back wall of the pharynx, their own operation may "not go down to the hand" resulting in sampling is not in place, generally operated by professionals to operate better.
Source | Yangcheng Evening News, Yangcheng Pie, Golden Sheep Network
Textu | Yangcheng Evening News all-media reporter Chen Hui Intern Zheng Minshan Correspondent Peng Fuxiang Liang Jiayun
Video | Provided by the First Affiliated Hospital of Sun Yat-sen University
Edit | Shushu
Proofreading | Li Hongyu
Review and sign | Zhou Lerui