Reduces the risk of “false positives” and the possibility of rapid antigen tests “killing good people by mistake”.
Writing | Johnny and
Source | “Medical Community” Public Account
Editor’s note:
The epidemic situation in Shanghai is generally stable and improving, and social clearance work has entered a critical period.
In order to prevent rebound, from May 1st to 7th, Shanghai adopted a combination of “nucleic acid + antigen” screening by division and classification. At the same time, on May 3, a press conference on the prevention and control of the new coronary pneumonia epidemic in Shanghai came out that, for the epidemic prevention management of the staff in the delivery industry, “three daily inspections” were carried out, that is, in addition to one nucleic acid test per day, it was also necessary to complete Antigen test 2 times a day. Express riders must upload a 24-hour nucleic acid negative report and verify it before issuing and running orders.
Hokkaido University Master of Neuroscience, Weibo Medical V “Zhuang Shilihe” wrote an article, analyzing the significance of antigens twice a day. The full text is as follows.
A lot has been said about the principle of rapid antigen detection before, so I won’t repeat it here. Compared with nucleic acid detection, the false positive rate of rapid antigen is relatively high, so two days ago, it was said that orange juice, lemon juice and cola may be detected with two bars. The reason may be related to acidity, or it may be different. s reason. Detecting two bars with orange juice is of course a false positive.
On how to reduce the possibility of false positives of rapid antigen, some related researches have been done abroad. For example, in March this year, Weill Cornell Medical College in New York released a study on JAMA Network Open.
The study included rapid antigen test data from nearly 180,000 subjects. None of them had any major symptoms of the new crown, and the sampling samples were nasal swabs. If the subject is positive for the first rapid antigen test, a second rapid antigen test is required 1 hour later. All nasal swab samples will be tested for nucleic acid (RT-qPCR) for confirmation. This is equivalent to setting nucleic acid detection as the gold standard.
First step, 623 people (0.35%) tested positive for the first rapid antigen test. The nucleic acid test found that 238 (38%) of the 623 people were true positives.
Second step, Of those who were first antigen positive, 569 (91%) followed up with a second rapid antigen test:
1. 224 of them were also positive for the second rapid antigen. The nucleic acid test found that 207 (92%) of the 224 were true positives;
2. 345 of them (569-224) were negative for the second rapid antigen. The nucleic acid test found that 328 (95%) of the 345 people were true negative.
Combining true positive and true negative results, the overall estimated accuracy of the second rapid antigen test was 94%.
The researchers believe that using nucleic acid testing as a standard, in asymptomatic people, two independent and consecutive rapid antigen tests can significantly improve the accuracy of positive results.
Therefore, in order to solve the problem of false positives in the rapid antigen test, it is an effective method to use nucleic acid test for verification, or to conduct a second independent rapid antigen test in a short period of time.
But note that this is to reduce the risk of “false positives”. In other words, it is to reduce the possibility of “killing a good person by mistake” by rapid antigen testing.
There is currently insufficient research evidence to show that multiple rapid antigen tests within one day can reduce the possibility of “false negatives”, or can accurately screen more infected people.
It is beyond my knowledge to do two antigen tests in addition to nucleic acid tests in one day. I personally think that the rapid antigen test once a day is completely sufficient, and there is no need to waste anti-epidemic materials.
References:
[1]Comparative Effectiveness of Single vs Repeated Rapid SARS-CoV-2 Antigen Testing Among Asymptomatic Individuals in a Workplace Setting.JAMA Netw Open.2022;5(3):e223073.doi: 10.1001/jamanetworkopen.2022.3073
Source: Medicine
Editor in charge: Xu Liyan
Proofreading: Zang Hengjia