With the development of normalized nucleic acid work in the society, it is particularly important to ensure the accuracy of nucleic acid detection . Since a large number of nucleic acid samples are tested in the laboratory every day, the probability of positive results will also increase. The current social screening has undergone great changes compared with early community screening. Once a positive test is found, close contacts from different communities and units may be involved, not limited to a certain place of residence. The confirmation of positive tests should be more cautious.
Unreviewed isolation has caused controversy
According to First Financial , the review work of people with positive initial screening in some places is carried out after they are sent to quarantine. After some people were sent to quarantine, the nucleic acid review turned negative, and there is indeed a possibility of "unfair and false cases".
Relevant persons from Shenzhen disease control department said: "For those who have had positive screening, they have been sent to quarantine, but the diagnosis must be confirmed after the disease control review." That is to say, "isolate first, then diagnose." Before the review, the persons who have positive screening have been quarantined.
In fact, it is common for people who have positive initial screening to be sent to quarantine without review. A reporter from the First Financial Daily learned from the Hangzhou disease control field that people with positive screening need to be isolated as soon as possible. But at present, most places do not have clear regulations on quarantine locations.
"According to the epidemic prevention requirements, people who have initial positive screening but do not have single-person living conditions are required to be sent to the isolation point, but the problem is that the facilities at the isolation point must at least be able to ensure single rooms and avoid cross-infection." A disease control expert told the First Financial Daily reporter, "In this way, if someone is isolated because of false positive , it will not become 'really positive' during the quarantine period."
In the recent round of epidemics in China, there are quite a few who are sent to the isolation for "false positive". Some netizens reported that they were isolated after being diagnosed as positive for nucleic acid. After entering the cabin, they both reviewed negative again and were "returned". Some people were "returned" and were quarantined at home. They tested positive during the home quarantine and infected the people they lived with.
In response to this situation, an infectious disease expert explained to the First Financial reporter: "It is very likely that they were 'false positive' for the first time. They were infected after entering the temporary cabin, but the nucleic acid during the incubation period was negative. After returning to their residence, the symptoms appeared. This situation is easily mistakenly considered that 'refalse positive' has infected the family, but it is actually the first infection."
A relevant person told the First Financial reporter: "These people who are isolated because of false positive are actually not only affected. His family, and even the neighbors who are sitting in the hospital will be implicated, which also causes a huge waste of social resources."
The above-mentioned person told the First Financial reporter that in principle, all positive samples in the initial screening should be reviewed, but due to the limitations of resources and manpower, the actual situation is not the case. "Even with the current sharp decline in the number of cases in China, not all the people sent to quarantine have undergone re-examination," he told the First Financial reporter.
Strengthen review to avoid isolation and decoupling from diagnosis
How to avoid the adverse impact of the above situation on epidemic prevention and the waste of resources caused? Experts said that there is only review, review, and review again!
In fact, although nucleic acid testing is the "gold standard" of COVID-19 testing, 100% accuracy is still not guaranteed.
Recently, Li Jinming, deputy director of the Clinical Testing Center of the National Health Commission, explained two aspects of the problem of "false positive" in nucleic acid test, one is the remaining pollution of the amplified product. Due to the large-scale population screening, the workload of nucleic acid testing institutions is very high, and the time to clean the laboratory is reduced, causing laboratory contamination; secondly, some laboratories will report suspicious positive samples as initial positives, resulting in a certain probability of false positives during review.
Li Jinming said that during the nucleic acid testing process, some problems are difficult to avoid. Experts believe that this requires strengthening the review process, and one review can reduce the error rate by a hundred times or even a thousand times.
"Even if the accuracy of the nucleic acid detection reagent reaches 99.9%, there is still 0.1% error, which means that for every 1,000 people tested, there will be one test result that may be inaccurate, and review can greatly improve the accuracy of nucleic acid detection." An expert in the field of testing told the First Financial reporter, "For example, the error rate of one in a thousand will be reduced to one in a million through one review." The First Financial reporter learned that the laboratory has a formal processing process after a positive result occurs. According to experts from relevant testing institutions, the first thing to do is to use the testing reagents from different manufacturers for re-examination. If the second review is still positive, the results will be uploaded and reported to the regional disease control department. The disease control department will then review the sample. When the review is still positive, it will be reported to the previous level disease control department for re-examination. If it is still positive, it will be reported to the Health Commission for prevention and control measures.
"In this way, from the collection of samples to the final determination of positive, there have been many screenings, that is, when positive occurs, most of the results are reliable." The above-mentioned expert in the field of testing told the First Financial Daily reporter, "The reason why false positives still occur is often because there is no review in accordance with the standard procedures, and the possibility of errors after multiple reviews is slim."
However, the process for reporting positive results is mainly for review of confirmed cases and not for isolation. Experts recommend establishing an isolation process for those who are positive for the initial screening as soon as possible, and try to avoid the phenomenon of decoupling of the isolation and diagnosis links. One of the most important methods is to speed up the process of nucleic acid re-examination.
"Now, the nucleic acid re-examination of positive initial screening is specified by the disease control department, but if the disease control department is not strong enough, it is recommended that some large medical institutions can also provide review services, and it is not necessary for disease control to do it, because our purpose is mainly to issue results provided by multiple different laboratories to enhance the accuracy of testing." A public health expert told the First Financial reporter.
