Finishing: In Vitro Diagnostic Network
Source: Gene Valley, Impression of Sydney, the official website of the Chinese Embassy in Canada, released by Yichun, IVD practitioners
At the press conference held by the Joint Prevention and Control Mechanism of the State Council on the afternoon of November 12, Deputy Foreign Minister Luo Zhaohui stated that nucleic acid testing is a common practice and the accuracy rate is relatively high. Even so, since the implementation of remote nucleic acid testing in July, 40 30,000 nucleic acid test reports of 10,000 Chinese and foreign travelers have problems! There are still more than 3,600 cases that have become confirmed cases after entering China. This shows that any method is not 100% accurate. Therefore, the Ministry of Foreign Affairs, the National Health Commission and experts after repeated studies decided to implement "double insurance", in addition to nucleic acid testing, plus serum antibody testing, that is, IgM testing.
Luo Zhaohui emphasized that the requirement of “dual testing” is not to ignore the actual situation of each country and not to implement “one size fits all”. In the case that serum antibody testing is temporarily impossible, an additional nucleic acid test is used to replace serum antibody testing to strengthen the "double insurance".
In addition, in response to passengers traveling around in transit and facing a high risk of cross-infection, increased implementation of "dual testing" at transit locations. "Dual testing" is also not "one size fits all", and testing will be implemented at transit locations that meet the conditions of "dual testing"; at transit locations that do not meet the conditions of "dual testing", the Ministry of Foreign Affairs "12308" hotline and embassies and consulates abroad The consular insurance hotline is open 24 hours a day, and the staff of the Ministry of Foreign Affairs is on duty around the clock to deal with emergency situations.
Earlier, the Chinese Embassy in Australia has officially declared that it requires double-negative testing to return to China! Officially implemented on November 8th! This means that the new crown antibody supplementary nucleic acid combined screening has become an important barrier to "guard the country."
The original notice of the Chinese Embassy in Australia (partial):
In order to reduce the cross-border spread of the new crown epidemic, starting from November 8, 2020, Chinese and foreign passengers departing from Australia and taking flights to China must present a negative certificate of the new crown virus nucleic acid test and serum sampled in Australia within 2 days before boarding Specific IgM antibody (hereinafter referred to as serum IgM antibody) test negative certificate (double-negative certificate), apply for the green health code or health status statement with the "HS" logo.
In addition to the requirement to board the plane with a double-negative certificate, the embassy notice also reminds those who depart from the country where the embassy is located and transit to China via a third country must undergo a second nucleic acid test and serum IgM antibody test in the transit country, and set a test time limit.
Nucleic acid + serum antibody double negative test is required when returning home
Recently, the epidemic situation in many countries in Europe and South America has become urgent again. On October 28, local time, the three major regions of France, Spain, and the two regions of Greece announced that they would blockade again, while Peru extended the state of emergency that had been implemented for more than seven months.
In response to the rebound of the global epidemic, the Chinese embassies in the United States, France, the United Kingdom, Ireland, Italy and other embassies have successively issued the "Notice on the need to board the plane with double-negative certificates for new crown virus nucleic acid testing and serum antibody testing for passengers travelling to China. ", the notice clearly stated that in order to control the cross-border spread of the epidemic and protect the health and safety of passengers, passengers travelling to China must board the plane with a double-negative certificate of nucleic acid test for the new coronavirus and serum antibody test.
Compared with before the implementation of the new regulations, the main updates are as follows:
1. Before the implementation of the new notice, only a nucleic acid negative certificate is required, and it can be issued within 3 days before boarding; now it is required to provide a nucleic acid and serum IgM double negative certificate 48 hours before boarding.
2. Before the implementation of the new notice, the place of nucleic acid testing will be the country of residence of passengers; after the implementation of the new notice, the place of nucleic acid + serum IgM testing will be the country of departure for direct flights to China.
What is the difference between the new coronavirus nucleic acid test, antibody test, and antigen test?
Nucleic acid testing and antibody/antigen testing are important means to confirm the new coronavirus, and one of the important processes for patients to confirm the diagnosis, but do you know what their testing principles are? What are the sample types? What kind of process is inspection and what are the problems? Today, the editor will give you some popular science~~
Novel coronavirus nucleic acid detection
Nucleic acid testing has the characteristics of early diagnosis, high sensitivity and specificity, and is the "gold standard" for diagnosing new coronary pneumonia. Currently, the most widely used real-time fluorescent quantitative RT-PCR technology. Generally, the two targets located on the ORF1ab and N genes of the virus are detected. The same sample must meet the double target positive or the repeated test as single target positive, or the two samples must meet the single target at the same time to confirm the positive of SARS-CoV-2 virus nucleic acid.
1. Principle of nucleic acid detection kit?
The unique gene sequence of the virus is used as the detection target. Through PCR amplification, the target DNA sequence we choose increases exponentially. Each amplified DNA sequence can be combined with a fluorescent-labeled probe that we added in advance. , Produce fluorescent signal, the more target genes amplified, the stronger the accumulated fluorescent signal.
In samples without virus, since there is no target gene amplification, no increase in fluorescence signal can be detected. Therefore, nucleic acid detection is actually to determine whether there is viral nucleic acid in the sample by detecting the accumulation of fluorescent signals.
2. What are the types of nucleic acid testing samples?
Generally nasal swabs, throat swabs, nasopharyngeal swabs, sputum, bronchial lavage fluid, alveolar lavage fluid, etc.
3. Five steps to detect the new coronavirus
The detection procedure needs to go through five steps: sampling, sample retention, preservation, nucleic acid extraction, and computer testing, which require rigorous scientific experiments to complete.
(1) Wipe the posterior pharyngeal wall and bilateral pharyngeal tonsils with a throat swab 5-10 times each, and rotate the swab continuously;
(2) Medical personnel are required to retain the sample, immerse the swab head in the cell preservation solution, and immediately tighten the tube cap after breaking the tail;
(3) Preservation, put the sample tube in a sealed bag and send it for inspection in time, and the inspection process requires a strict transportation environment, stored at 2-8 degrees Celsius.
(4) Operate nucleic acid extraction, and extract nucleic acid from the sample after inactivated virus for subsequent detection. Automatic equipment, such as nucleic acid extractor, can be used.
(5) Fluorescence PCR nucleic acid detection, that is, machine detection, it takes 70-80 minutes for the extract to undergo fluorescent PCR amplification reaction.
4. What are the problems with nucleic acid detection?
False negative, due to improper sampling, improper specimen storage, the use of different types of specimens, and the use of reagents from different manufacturers may cause the nucleic acid test results to be "false negative" and missed diagnosis; high requirements for detection equipment or platforms, high sensitivity RT-PCR The instrument is expensive, and requires high laboratory cleanliness and operators. Nucleic acid detection takes a long time. It usually takes 4-6 hours to complete an RT-PCR test. However, considering sample transportation and a large number of sample backlogs In this case, the results can usually be reported within 24 hours at the earliest.
Therefore, when the nucleic acid test is negative, adding IgM and IgG antibody detection can make up for the shortcomings of the nucleic acid test that is likely to cause missed diagnosis.
5. What is the serum IgM antibody test?
Serum antibody testing and viral nucleic acid testing can be used as double insurance for diagnosis. When the nucleic acid test is false-negative, the serum antibody test can help determine the presence or absence of virus in the tester and the virus infection.
★ After the virus invades the human body, the human body will produce IgM or IgG antibodies for defense. Serological testing is to detect the presence and content of IgM and IgG in the blood sample to indirectly determine the presence or absence of the virus and virus infection in the body.
★ It takes a certain incubation period for antigens to enter the body before IgM and IgG are produced. During this period, IgM and IgG could not be detected. At this time, the advantage of nucleic acid testing is reflected. It can detect whether patients in the window period are infected and find the infected as early as possible.
★ Compared with nucleic acid testing, serological testing is convenient for sampling, simple to operate, and easy to interpret. Therefore, the combined use of nucleic acid testing + serum antibody testing can help improve the disease detection rate.
The English name of serum IgM antibody tests is COVID-19 rapid antibody tests. The detection process is very simple, collect blood, drip the blood into the test strip, and the result will be available after 15 minutes.
The result is visible to the naked eye, there are two situations that meet the requirements:
1. If it is negative, only the quality control line (C) appears, and the test lines G and M are not visible, it means that no new coronavirus antibody has been detected and the result is negative.
2. Positive result, G only: If the quality control line (C) and the test line G appear at the same time, it means that the new coronavirus IgG antibody has been detected, and the result is IgG antibody positive. It means that once had the new crown, now he has recovered and has antibodies.
Can the two tests of serum IgM and IgG antibodies of the new coronavirus replace the two tests of nucleic acid and serum IgM antibodies?
In this regard, the Chinese Embassy in Canada has a clear explanation: According to the notification requirements of the Chinese Embassy and Consulate in Canada, passengers taking flights from Canada to China must complete the sampling and testing of new coronavirus nucleic acid and serum IgM antibodies within 48 hours before boarding. Only do serum IgM antibody and IgG detection or other types of detection, and cannot replace nucleic acid and serum IgM antibody detection. You must complete the new coronavirus nucleic acid and serum IgM antibody tests within 48 hours before boarding as required.
6. How to understand IgM and IgG in serum antibody testing?
The detection of new coronavirus nucleic acid/antibody/antigen has its own focus and cannot be substituted for each other. Multiple detection methods are combined and used to complement each other. They combine molecular biology and immune level detection to give full play to their respective advantages and improve sensitivity and specificity. Effectively shorten the detection window, increase the positive detection rate, and provide double protection for all possible risk groups.