Global COVID-19 response still faces serious challenges
In the course of the recent global fight against the epidemic, due to the economic downturn, while the Omicron strain is less pathogenic than previous strains, and the weak anti-epidemic mentality and other complex factors, some countries and regions have canceled the wearing of masks, isolation of infections and strict Control measures such as contact tracing. Apart from strengthening vaccination, basically no other prevention and control measures are taken.
In response, the WHO issued a new warning to the world: "While in many countries all restrictions have been lifted and life looks much like before the pandemic, reported cases are increasing in nearly 70 countries in all regions." Experts It is believed that due to this spreading variant, which has a stronger transmission ability, quarantine measures in some countries have been relaxed prematurely, and the future trend of the epidemic is still unclear.
To help end the emergency phase of the novel coronavirus pneumonia epidemic, WHO calls on countries to continue to strengthen virus surveillance capabilities to detect early warning signs of major virus evolution. Current nucleic acid testing is an important part of virus surveillance. Nucleic acid testing is a mature and internationally used laboratory diagnostic method. The editor is here to do some simple science popularization.
Part 01
Nucleic acid detection principle
Nucleic acid testing is a test for the presence of nucleic acid (RNA) in the human body. Each virus contains ribonucleotides within its nucleic acid, and different viruses contain different numbers and sequences of ribonucleotides, making each virus specific.
Nucleic acid detection is a specific detection of nucleic acids. Before nucleic acid testing, sputum, throat swabs, alveolar lavage fluid, blood and other samples can be tested to find the subject's respiratory tract infection bacteria. Nucleic acid detection is usually performed on throat swab samples and will be purified by lysis to extract possible nucleic acids.
Nucleic acid detection is mainly performed through fluorescence quantitative rt-PCR. In the detection process, RT-PCR is first used to reverse-transcribe nucleic acid (RNA) into its corresponding deoxyribonucleic acid (DNA). The obtained DNA is then replicated in large quantities using fluorescence quantitative PCR technology. At the same time, the cloned DNA is detected and labeled with specific probes. The instrument detects a fluorescent signal if nucleic acid is present, and indirectly detects it as the fluorescent signal increases as the DNA replicates.
Part 02
Nucleic acid testing is the “gold standard” for diagnosis
Regarding nucleic acid testing, it is a mature and internationally recognized laboratory diagnostic method. In the past, we mainly detected viral pathogens through culture and identified them through staining, morphological observation, biochemical tests, immunological tests and other methods. Viruses take a long time to grow, and some pathogens are difficult to grow in the laboratory before we perform nucleic acid testing. The nucleic acid detection method has high sensitivity and methodological specificity of up to 100%. In other words, a positive result of a nucleic acid test is the gold standard for diagnosis, the same as the result of pathogen culture. Not only that, common pathogens such as hepatitis B virus and HIV can also be diagnosed through nucleic acid testing and treatment monitoring can be performed.
Part 03
A positive nucleic acid test in an environmental sample does not mean the presence of live virus
A positive nucleic acid test does not necessarily mean the presence of live virus in the environmental sample. In order to identify the presence of viable virus, it is necessary to perform viral isolation in cells or in sensitive mice to determine whether viable virus is present. Because dead viruses and live viruses in environmental samples and the inactivated new coronavirus pneumonia vaccine we are currently using all contain nucleic acids, nucleic acid tests can be positive, so a positive nucleic acid test does not mean that it contains live viruses and requires comprehensive evaluation.
Part 04
Nucleic acid testing sampling swabs are medical devices, not cotton swabs, and are non-toxic and harmless
Q-tips look like Q-tips, but they are not. It is made of polyester or nylon fiber. During the process of making a swab, millions of tiny fibers are vertically and evenly covered at the tip of the swab handle. When you take a sample, an oropharyngeal swab, like a toothbrush when brushing your teeth, you brush the back wall of the pharynx in your mouth to get the cells, then you put the swab into a test tube and then you take the sample out into a preserving solution , and then you test it in the lab.
Sampling swabs are a kind of medical device. Their production environment and requirements are very strict, and there are relevant quality supervision standards. The most basic standard is that they are non-toxic and harmless, and no harmful substances are produced during the production process.
Part 05
Large population screening is usually performed with oropharyngeal swabs
Depending on the sampling location, samples are divided into upper respiratory tract samples (such as nasopharyngeal swabs, oropharyngeal swabs) and lower respiratory tract samples (such as sputum). The sputum virus content and positivity rate were the highest in swabs, followed by nasopharyngeal swabs and oropharyngeal swabs. In the infection, the main symptoms are dry cough, phlegm without saliva, and it is difficult to obtain. Nasopharyngeal swab collection requires high operation of the sampler and the sampling process is slow. Although the positivity rate is high, it is not usually used to screen the majority of the population but can be used to sample isolated populations. Swab sampling is relatively simple and fast, so we usually use it.
Part 06
Is a positive nucleic acid test a diagnosis?
A positive nucleic acid test can confirm that viral nucleic acid is in the person's body but does not directly confirm it. If the nucleic acid test is positive, participants. Participants can be diagnosed as confirmed cases if they have the following symptoms: and a history of contact with confirmed infected persons.
If the participant does not have any symptoms, the participant may be diagnosed as an asymptomatic carrier. Asymptomatic carriers are also contagious, and some asymptomatic carriers later develop symptoms and become confirmed patients.
Part 07
Why do false negatives happen?
A false negative means that the person being tested has been infected with COVID-19, but no viral nucleic acid has been detected, that is, the nucleic acid test is negative. If a person is asymptomatic and the nucleic acid test is negative, it is easy to relax his vigilance, which may lead to wider spread of the virus.
There are three main reasons for false negatives:
First, the nucleic acid content in the original test specimen was too low, below the detection limit. This is related to the type of sample collected and the time of collection.
Secondly, if the nucleic acid binding to the probe changes, it may affect the binding efficiency of the probe in the detection, and the fluorescent signal cannot be detected.
Third, false negatives are also related to the acuity of the testing technique. In the early stages of the epidemic, clinical kits were not mature and sensitive enough, and false negative reports often occurred. Later, as technology improved, the accuracy of the test rapidly increased and the false negative rate continued to decrease.
Part 08
Positive nucleic acid test
There are three types of positive nucleic acid tests followed by repeated negative tests.
In the first scenario, an initially uninfected person becomes infected at a later point in time and then tests positive.
In the second case, during the incubation period, the nucleic acid test was not detected and the test was positive after the start.
In the third case, although the virus was present at the beginning, the payload did not reach the detection limit. Currently, the test is negative, but after a high load, the test is positive.
Hecin's Fast PCR Solution
As of 1st 2022, the infection has resulted in more than 540 million infections and more than 6 million deaths. In human hosts, in order to adapt to the internal environment, viruses will accelerate mutation and evolution. The mutated virus may change in infectivity, incubation period, infectivity, pathogenicity, duration in the body, antigenicity, etc. Variants occur frequently, spread rapidly around the world and have high infection rates, making the epidemic more complex and severe. Therefore, professional monitoring and judgment methods are very important.
Hecin actively responds to the needs of novel coronavirus pneumonia prevention and control with a new set of rapid PCR solutions, including specimen release agent, 2019-nCoV nucleic acid detection kit (PCR-fluorescent probe method) and ultra-fast QPCR instrument. This protocol can save 70% time and produce results compared to traditional protocols. In terms of performance, sensitivity and specificity were greater than or equal to 98%. It can detect a variety of mutant strains, such as Delta and Omicron, and provides high-quality, stable, and convenient nucleic acid testing services to support the global response to COVID-19. The products have passed through the European Union, Brazil, Indonesia, Thailand, the United Kingdom, Bolivia and other countries and regions, and can be exported smoothly.
Long-distance cold chain logistics transportation is one of the biggest obstacles to overseas exports of nucleic acid testing kits. For conventional liquid detection reagents, the temperature control link during transportation greatly affects the performance of the reagents, and the transportation cost increases exponentially. Hecin's 2019 ncov nucleic acid detection kit (PCR-fluorescent probe method) uses freeze-dried powder technology, does not require a cold chain, and can be stably transported and stored at room temperature, greatly reducing transportation costs.
At the same time, the Hexin Restaurant 2019 ncov nucleic acid detection kit (PCR-fluorescent probe method) has passed the system and can be adapted to a variety of PCR instruments (ABI7500, HC 1600, etc.) to ensure the 2019ncov nucleic acid detection kit.
So far, he has successfully developed a variety of breath detection reagents, including:
2019 ncov nucleic acid detection kit (PCR-fluorescent probe method),
2019 ncov/IAV/IBV nucleic acid detection kit (PCR-fluorescent probe method),
2019 ncov antigen detection kit (colloidal gold method),
2019 ncov neutralizing antibody detection kit (fluorescence immunochromatography),
2019 ncov IgM/IgG Antibody Detection Kit (Colloidal Gold Method),
2019 ncov and delta strain nucleic acid detection kit (PCR-fluorescent probe method),
2019-nCoV and Omicron variant nucleic acid detection kits (PCR-fluorescent probe method), etc.
Hecin is committed to creating a complete set of respiratory detection solutions suitable for a variety of scenarios. Hecin will continue to track the changes in the global epidemic, strictly control product quality, and continue to contribute to the epidemic prevention and control work in various countries around the world.
