Here comes the guide| Here is what you want to know about antigen testing under the COVID-19 epidemic

 Here comes the guide| Here is what you want to know about antigen testing under the COVID-19 epidemic

Under the influence of the current epidemic situation, our life has been limited to a certain extent. Making nucleic acid every day has become a necessary thing in our life. However, with China’s defense measures against the epidemic, China has introduced two methods of nucleic acid detection:

First, self-examination.

Second, the medical staff will carry out nucleic acid testing.

For the two kinds of nucleic acid detection, we hope we can pay attention to the following points:

1、 Self nucleic acid detection

（1） Preparation before antigen self-test

1. Wash hands. Wash hands with flowing water or hand disinfectant.

2. Understand the testing process. Carefully read the supporting instructions of antigen self-test reagent and relevant precautions for antigen self-test.

3. Reagent preparation. Check whether the antigen self-test reagent is within the warranty period, and check whether the nasal swab, sampling tube, test card and other contents are missing or damaged. If the reagent is expired or the contents of the reagent are missing or damaged, the test reagent shall be replaced in time.

4. Confirm the requirements for ambient temperature and humidity. The colloidal gold test strip is generally required to be tested under the normal temperature of 14 ℃ – 30 ℃, so as to avoid abnormal test results caused by supercooling, overheating or excessive humidity. The antigen detection card shall be placed in a flat and clean place after unpacking.

（2） Sample collection

The self inspector first blows his nose with toilet paper. Carefully unpack the nasal swab to avoid contact with the swab head. Then, tilt the head slightly, hold the tail of the swab in one hand and stick it to the nostril of one side, and slowly penetrate 1-1.5cm backward along the bottom of the lower nasal tract. After that, rotate the swab to the nasal cavity for at least 4 circles (the dwell time is not less than 15 seconds), and then repeat the same operation for the other nasal cavity with the same swab.

（3） Antigen detection

1. According to the reagent instructions, put the nasal swab after collecting the sample into the sampling tube immediately. The swab head should be rotated and mixed in the storage solution for at least 30 seconds, and at the same time, squeeze the swab head by hand across the outer wall of the sampling tube for at least 5 times.

2. Squeeze the liquid of the swab head through the outer wall of the sampling tube and discard the swab. After the sampling tube is covered, drop the liquid vertically into the sample hole of the detection card.

3. According to the reagent instructions, wait for a certain time before reading the results.

4. The results are interpreted as follows:

Positive results: red or purple bands are shown at “C” and “t”, and the bands at “t” can be dark or light, which are all positive results.

Negative results: red or purple bands are shown at “C” and no bands are shown at “t”.

Invalid result: no red or purple band is displayed at “C”, no matter whether the band is displayed at “t”. The result is invalid, and the test strip shall be taken again for retest.

（4） Waste disposal.

1. Isolate the observer. No matter whether the test results are negative or positive, all used sampling swabs, sampling tubes, test cards, etc. shall be put into sealed bags, and the management personnel shall refer to the medical wastes or dispose according to the procedures.

2. Community residents. If the test result is negative, all nasal swabs, sampling tubes and test cards after use shall be put into sealed bags and treated as general garbage; If the test result is positive, the personnel shall be transferred to the medical institution for treatment as medical waste.

The novel coronavirus antigen detection kit is coming, and science popularization keeps up!

 The novel coronavirus antigen detection kit is coming, and science popularization keeps up!

What are the precautions in the use of novel coronavirus antigen detection kit?

1、 Characteristics of antigen detection of novel coronavirus

2、 Precautions for use

1.    Before testing,      the manual shall be carefully read.    Sample sampling and processing shall be carried out in strict accordance with the manual. Attention shall be paid to the depth of the swab, the part in contact with the human tissue, the contact time, the contact strength, the operation method, the dripping amount of sample extract, and the waiting time for sample testing.

2. Do not open the inner package before it is ready. Use it as soon as possible after opening the inner package.

3. Do not suck the sample with your mouth.

4. When handling these items, do not smoke, eat, drink, make-up or wear contact lenses.

5. Disinfect the spilled sample or reagent with disinfectant.

6. After the test, no matter whether the test result is negative or positive, the used swabs, sampling tubes, test cards and other wastes shall be put into sealed bags and shall not be discarded at will.

7. Do not use expired kits.

3、 How to report adverse events?

      Adverse events of medical devices refer to all kinds of harmful events that occur under the normal use of the medical devices that have been listed and cause or may cause human injury. Common adverse events of testing reagents include non display of results, inaccurate measurement, etc. If the public finds any adverse event when using novel coronavirus antigen detection reagent, they can report it to the registrant (recorder), business enterprise or treated medical institution, or to the local adverse event monitoring institutions,

What is the antigen in the novel coronavirus antigen detection kit?

 What is the antigen in the novel coronavirus antigen detection kit?

               The interaction between antigen and antibody is the basis of immunochemistry. As an effective research tool, it is necessary to know how the antibody binds to the corresponding antigen. The characteristics of the interaction between antigen and antibody mainly include the following three points:

1. Specificity of antigen antibody binding

        Antigenic determinants interact with the antigen binding sites of antibodies in a non covalent manner,        and they must be in close contact at the empty space to generate sufficient binding force. The complementary structure between molecules determines the specificity of antigen antibody binding. Among them, there are four kinds of interactions or affinities between antigen and antibody molecules: hydrogen bond, ionic bond, hydrophobic interaction and van der Waals interaction.

         Minor changes in antigen structure will affect the strength of antibody antigen interaction. The loss of a hydrogen bond at the interface reduces the strength of the interaction. The interaction is the balance between the attractive force and the repulsive force of the contact surface. The change of amino acid residues at the binding site can also change the intensity of antigen antibody interaction.

2. Reversibility of antigen antibody binding

       Affinity was used to measure the binding strength of epitope and antibody. The noncovalent binding of antigen and antibody is reversible (Fig. 3), and the intensity of the interaction can be described as an equilibrium reaction. If [AB] is the mass concentration of the free antibody binding site, [Ag] is the mass concentration of the free antigen binding site, and [abag] is the mass concentration of the antigen antibody complex, the affinity calculation formula is [abag] / [AB] [Ag].

        The time to reach equilibrium depends on the diffusion rate, and the antibody with high affinity can bind the antigen in a shorter time than the antibody with low affinity. The application of high affinity antibody in immunochemistry is effective, which is related to its high activity and the stability of the complex. For example, the dissociation half-life of a high affinity antibody binding to a small molecule protein antigen is 30 minutes or more, while the dissociation time of a low affinity antibody is only a few minutes or less.

        The affinity of antibody antigen interaction is different, and the affinity constant of antibody antigen interaction is affected by temperature, pH and solvent. When these conditions are changed, it can be found that when the reaction equilibrium is reached, the number of antigen antibody complexes increases or decreases, which promotes the reaction to fully bind or dissociate the bound antigen. According to this characteristic, the antigen or antibody can be separated and purified by affinity chromatography.

3. Relationship between antigen amount and antibody reaction

         Affinity refers to the overall stability of antigen antibody complexes. The overall intensity of antibody antigen interaction is controlled by three factors: the intrinsic affinity of antibody to epitope, the valence of antibody and antigen, and the three-dimensional structure of reaction components. The antibody has multivalent binding ability, in which IgG and most IgA are bivalent and IgM is decavalent. The antigen may be multivalent or monovalent. Multivalent interactions can stabilize immune complexes

             If a multivalent antigen is mixed with a specific antibody in a test tube,   an immune complex can be formed. When the concentration of antigen and antibody is appropriate, that is, in the equivalent region,   antigen and antibody molecules are widely cross-linked through non covalent bonds to form large immune complexes. If the antigen is excessive,      due to the reversibility of the binding of antigen and antibody,    the free antigen will replace the bound antigen, dissociate the antibody that has bound the antigen, and cannot form a large immune complex. Similarly, if the antibody is excessive, the free antibody will replace the bound antibody, and the antigen bound to the antibody will be dissociated and will not form a large immune complex

         The three characteristics of antigen antibody interaction, i.e. the relationship between specificity, reversibility and antigen antibody reaction amount, are briefly described above. Antigen antibody reaction is the basis of immunochemistry.   For example,     humoral immunity is based on the binding of antigen and antibody molecules,       which can bind on the cell surface or in free form. Through the combination of antigen and antibody, the physiological effects such as regulation, precipitation, agglutination, phagocytosis and cell lysis are triggered to form a complete set of humoral immune functions of the body.

What are the types of antigens in the novel coronavirus antigen detection kit?

 What are the types of antigens in the novel coronavirus antigen detection kit?

Definition of antigen：

It is a substance that can combine with TCR of T and BCR (lymphocyte antigen receptor) of B, promote their proliferation and differentiation, produce antibodies or sensitized cells, and combine with them to exert immune effects.

Two characteristics of antigen：

Immunogenicity

The ability of antigen to stimulate the body to produce immune response, induce antibodies or sensitize lymphocytes.

Able to stimulate response

antigenicity：

Antigen has specific binding ability with the its induced antibody or sensitized lymphocyte

The product (antibody, etc.) after the stimulation reaction can specifically bind to itself

The classification guided by this: immunogen = complete antigen, incomplete antigen (only antigenicity) = hapten

Factors influencing immunogenicity

A.Contribution of the antigen

The following are all positively related

1.Size

2.Chemical complexity

3.Chemical composition

4.Conformation and accessibility

5.Physical form

B.Contribution of the interaction between host and antigen

Specificity:

Specificity refers to the specificity that the antigen stimulates the body to produce an immune response and the reaction of its response products = a specific antigen can only stimulate the body to produce specific antibodies or sensitized lymphocytes, and can only specifically bind to the antibody or lymphocytes that respond to the antibody.

the types of epitope

conformational epitope& sequential epitope

TCR & BCR

Type of antigen:

TD Ag (thymus dependent antigen): this kind of antigen stimulates B to produce antibodies that depend on t help, also known as T cell dependent antigen. [most human proteins are]

Ti Ag (thymus independent antigen): this kind of antigen stimulates B to produce antibodies independent of t help, also known as T cell dependent antigen.

Compared with the two, TD AG is more versatile:

Nonspecific immunostimulators:

Not typical but awesome

Superantigens are generally:

Extracellular toxin, retroviral protein

TCR binding site V β \ beta β

Direct stimulation of T cells

The reactive cells were CD4 + T cells

MHC binding site: non polypeptide region

Mitogen

Also known as mitogen, it can cause cells to undergo mitosis and then proliferate.

It is an important mitogen that acts on T and B cells of human and mouse.

Experimental study on inactivation of disposable virus sampling tube

Experimental study on inactivation of disposable virus sampling tube

Virus sampling tube:

Disposable virus sampling tube (inactivated type)

Experimental materials:

Lentivirus (gkai gene, gcnl0319432), HEK293T cells

Nucleic acid extraction kit and extractor:

（BNP027-2B, M32)

Xinguan sampling tube：

Experimental method:

Refer to the detection method described in the virus inactivation test in the technical specification for disinfection (2002 Edition) to determine the inactivation capacity of the virus preservation tube.

Step 1: cell culture

HEK293T cells in good growth state were digested and counted, and diluted with 1 × 104 / ml, according to 100 μ L / well volume, make three multiple wells for each gradient of virus, calculate the required number of inoculation wells, and slowly and evenly inoculate the cells into 96 well plates. Put it into a 5% CO2 incubator at 37 ° C and incubate overnight

Step 2: lentivirus dilution

The lentivirus with a titer of 107-108tu / ml was diluted by 10 fold gradient, and three gradients were continuously diluted.

Step 3: virus inactivation

Place the diluted virus at room temperature, mix it with the inactivated virus preservation solution (batch number: 220201 / 220207 / 220211) in a volume ratio of 1:1, and place it at room temperature for 1min, 5min and 10min respectively for inactivation.

Step 4: stop inactivation

The virus isolation medium (which can be replaced by DMEM complete medium) was diluted 1000 times to neutralize the inactivation preservation solution and terminate the inactivation.

Negative control: the mixture of virus isolation medium and inactivated virus preservation solution diluted 1000 times;

Positive control: the mixed solution of virus isolation medium diluted 1000 times of virus original solution.

Step 5: virus incubation

The cell culture medium was aspirated from the previously cultured HEK293T cells, and 100 μ L of the prepared virus mixture, and the corresponding positive control and negative control. The virus was incubated for 3 hours, and was removed from the incubator and shaken every 30 minutes.

Step 6: cell culture

After the incubation, the virus solution was aspirated, and 100 μ L DMEM complete medium, place 96 well plates in a 5% CO2 incubator at 37 ° C, and observe the cell state.

Step 7: observation and counting of fluorescent cells

Continue to culture for 48-72h, and observe the cell state during the period. If the cell culture solution turns yellow, change the solution, count the wells with the appropriate number of fluorescent cells, and calculate the virus titer.

experimental result：

Experimental conclusion:

It can be seen from the data in Fig. 1 and table 1 that after lentivirus was inactivated for 1min, 5min and 10min, HEK293T cells grew normally under the microscope bright field; Three batches of inactivated virus storage tubes can effectively inactivate the virus after interacting with the virus for 5min.

Rapid detection of novel coronavirus infection pneumonia

 Rapid detection of novel coronavirus infection pneumonia

 In early 2020, coronavirus disease (covid-19) spread worldwide,      causing the world to face a crisis of survival and health. The automatic detection of lung infection through computed tomography     ( C T )    images provides great potential for strengthening the traditional health care strategy to cope with covid-19.   However, segmentation of infected areas from CT sections faces several challenges, including high variability in infection characteristics and low-intensity contrast of infection with normal tissue. In addition, it is unrealistic to collect a large amount of data in a short time,    which hinders the training of the depth model.    In order  to  meet  these challenges, this paper proposes a new covid-19 lung infection segmentation depth network, which can automatically identify the infected areas from chest CT slices. In the network, a parallel partial decoder is used to aggregate high-level features and generate global graphs. Then, implicit inverse attention and explicit edge attention are used to model and enhance the boundary representation. In addition, in order to alleviate the shortage of labeled data,   a semi supervised sequence configuration framework based on random selection propagation strategy is proposed.    This framework only needs a small number of labeled images and mainly uses unlabeled data. Semi supervised framework can improve learning ability and achieve higher performance.       Extensive experiments on covid semiseg and CT show that the proposed inf net is superior to most tip segmentation models and improves the latest performance.

1. The texture, size and position of the infection in CT sections vary greatly, which is challenging to detect. For example, the combined area of the whole piece is too small, which may easily lead to false negative of the whole piece of CT.

2. The variance between classes is small. For example, GGO boundaries are often low in contrast, fuzzy in appearance, and difficult to identify.

3. Due to the emergency of covid-19, it is difficult to collect enough marker data for the training of depth model in a short time.

1. By using the parallel partial decoder (PPD) to aggregate the features from the high level, the combined features obtain the context information and generate a global map as the initial guidance area for the subsequent steps. In order to further explore the boundary clues, we use a set of implicitly repeated reverse attention (RA) modules and explicit edge attention guidance to establish the relationship between regions and boundaries.

2. A semi supervised segmentation system based on the propagation of random selection is introduced to alleviate the short time of labeled data.

3. A covid-19 semi supervised infection segmentation (covid semiseg) dataset was constructed, including 100 labeled CT slices from the covid-19 CT segmentation dataset and 1600 unlabeled images from the covid-19 CT acquisition dataset

Edge map predicted with standard binary cross entropy constraint and edge map of ground truth value (GT):

Parallel partial decoder (PPD)

Reverse Focus module (RA)

    A random sampling strategy is used to gradually expand the training data set using unlabeled data. False labels were generated for unlabeled CT images using the procedure described in the following figure. Then the model is trained using the obtained CT images with false labels.

     The semi information network was extended to a multi class pulmonary infection detection framework to provide more abundant information for the further diagnosis and treatment of covid-19. The extension of the semi information network is based on the multi class marker framework guided by the infected area, as shown in the figure.

Well-aerated Lung on Admitting Chest CT to Predict Adverse Outcome in COVID-19

 Well-aerated Lung on Admitting Chest CT to Predict Adverse Outcome in COVID-19

Objective:    to determine the prognostic value of quantification of well ventilated lungs obtained on baseline chest CT in patients with covid-19 pneumonia。

Methods:    open source software (% s-wall and absolute volume, vol-wall) and CT were used for visual quantification (% v-wall) and quantitative analysis (% s-wall and absolute volume, vol-wall) of well ventilated lungs. Clinical parameters included demographics, comorbidity, symptoms and duration of symptoms, oxygen saturation, and laboratory values. Logistic regression analysis was used to evaluate the relationship between clinical parameters, CT indicators and patient prognosis (ICU admission / death and no ICU admission / death). The model performance is determined by calculating the area under the receiver operating characteristic curve (AUC).

Results: 236 patients (59 / 123, 25%; median age, 68 years) were included in this study. Compared with the clinical model containing only clinical parameters (AUC, 0.83), all three quantitative models showed higher diagnostic performance (AUC of 0.86 for all models).

Conclusion: in patients with confirmed covid-19 pneumonia, visualization or software quantification of CT lung abnormalities is a predictor of ICU admission or death

Background:

CT quantitative display of well ventilated lungs is helpful to evaluate the filling of alveoli during ventilation or predict the prognosis of patients with acute respiratory distress syndrome

Method:

Open source 3D slicer software (version 4.10.2, https://www.slicer.org )。 B40f kernel is used to realize automatic segmentation and analysis of lung parenchymal histogram. When the lung segmentation effect is not ideal, the user uses manual tools to correct the lung contour

Filtering of data:

Patients were divided into two groups:Patients admitted to ICU or died (ICU / death) and patients discharged without admission to ICU. The time between CT and ICU admission or death was recorded

result:

The results of this study suggest that the proportion of well ventilated lungs assessed by chest CT obtained in the emergency department is associated with a better prognosis in patients with covid-19 pneumonia, but not with other clinical parameters

Discussion:

Obesity has been described as a common comorbidity in hospitalized patients with H1N1 influenza infection. Previous observations suggest that covid-19 may have a more severe course in obese patients. Therefore, CT evaluation of adipose tissue may be an objective marker of obesity and has prognostic significance.

Novel coronavirus vaccine: more than 100 kinds are under development and 8 kinds are in clinical trials

 Novel coronavirus vaccine: more than 100 kinds are under development and 8 kinds are in clinical trials

     The clearest way to get rid of the novel coronavirus crisis is to develop a safe and effective vaccine. Scientists have not wasted any time and have been working hard. At least 102 candidate vaccines are under development worldwide, and eight of them have been tested in humans. At least two monkeys have been protected from novel coronavirus (sars-cov-2), which causes novel coronavirus.
Some optimistic vaccine developers said that if everything goes well, we may see large-scale production and limited vaccine deployment as early as this autumn. If true, it would be an extraordinary achievement. Less than four months ago, sars-cov-2, an unnamed and never seen virus, suddenly appeared in Wuhan, a city in Central China. Researchers there quickly discovered it and deciphered and shared its genetic code in late January, enabling researchers around the world to work hard to defeat it. By late February, many researchers were conducting clinical trials for candidate vaccines. By the middle of March, two of them started to take action, and the volunteers began to receive the first batch of candidate vaccines against novel coronavirus.

This is a record setting feat. But it is not clear whether researchers can maintain this breakthrough.

      Generally, vaccines must undergo three more rigorous human trial phases before they are considered safe and effective. These phases assess the safety of candidates, the intensity of the immune response they trigger, and their ability to actually protect people from infection and disease.

     Most candidate vaccines have failed to do so. It is estimated that more than 90% of the candidates failed. Although it is conceivable that the schedule of the novel coronavirus pandemic may deliver vaccines in a short period of 18 months, most vaccines take several years (in fact, usually more than 10 years) to get from the preclinical review to the syringes in the doctor’s office.

     Cancelling this schedule may increase the risk of failure. For example, candidate vaccines usually enter the three stages of clinical trials only after they have been fully tested in laboratory animals that can simulate human diseases. However, no animal model of novel coronavirus has been established for this new virus. In a catastrophic pandemic, there is not enough time to fully develop vaccines. Now, some researchers are working on ground animals at the same time as human experiments.

      Researchers have reason to worry about the safety of any novel coronavirus vaccine. When they tried to make vaccines against some coronavirus relatives of sars-cov-2 in the past, they found that candidate vaccines seemed to worsen the infection in a few cases. That is, these candidate vaccines seem to promote the immune response of rabies, causing lung damage in monkeys and liver damage in ferrets. Researchers still do not fully understand this problem, nor do they know whether it may occur in humans, let alone whether it will appear with a new candidate vaccine against sars-cov-2.

      RNA and DNA vaccines: These are the latest types of vaccines and the most unstable. There are currently no licensed vaccines using this method. But researchers are optimistic about its potential.

        Moderna cooperated with the National Institutes of health to conduct a clinical trial in February, and the first dose of treatment was given to humans on March 16. If everything goes according to plan, the company suggests preparing vaccines for front-line medical personnel by the fall of this year.

      At the same time, cansino biologics, a Chinese biotechnology company, began testing its candidate vaccine based on viral vectors on March 17. This strategy packages the genetic material of sars-cov-2 into a weakened adenovirus strain, and the company has started phase II trials.

    Sinovac biotech, headquartered in Beijing, made headlines this month after its whole virus inactivated sars-cov-2 vaccine candidate was proved to protect a few monkeys from novel coronavirus in early laboratory tests. Its first phase of human clinical trial began on April 16. The results are positive, but some researchers are eager to see more testing and safety data.

    Researchers at the University of Oxford have also started a good start in developing vaccine candidates based on viral vectors. They packaged sars-cov-2 spike protein in weakened adenovirus, similar to cansino’s method. Like Sinovac, their vaccine also protected a small number of monkeys in early laboratory experiments. Researchers at the University of Oxford began dosing the participants last week. The researchers told the New York Times that if these trials were carried out as planned, they could produce millions of doses by September.

Novel coronavirus (sars-cov-2) antigen detection kit

 Novel coronavirus (sars-cov-2) antigen detection kit

https://youtu.be/ZCVWNVV

1. Nasopharyngeal swab sample collection

1. Tilt the patient’s head slightly back approximately 70°.

2. Gently insert the sampling swab into the nostril, straight back (not up), along the base of the nasal passage, until it reaches the back wall of the nasopharynx—usually half the distance from the corner of the nose to the front of the ear (approximately 4 to 6 cm) or 1.6-2.5 inches). Note: Do not rub too hard – if you experience a blockage, try the other nostril.

3. Gently rub and roll the swab 5 times.

4. Slowly pull the swab out while rotating the swab. 

2. Swab Specimen Preparation

1. Peel off the aluminum foil seal from the sample extraction tube;

2. Put the swab into the sample extraction tube and stir the swab in the solution at least 5 times;

3. Squeeze the sample extraction tube and move the swab up and down at least 3 times to drain any sample solution in the swab. Discard swabs correctly;

4. Firmly insert the cap on the sample extraction tube. The tubes were left for 1 minute to release viral antigens.

3. Instructions for use

1. Flick the bottom of the tube to mix the sample solution.

2. Remove the test cartridge from the foil bag. Put the test box on the table. Squeeze the sample extraction tube vertically upside down to discharge 3 drops of sample solution into the “S” shaped hole on the test box.

3. Read the results after 15 minutes. Positive results are visible in as little as 1 minute. Negative results must only be confirmed at the end of 15 minutes. Any results interpreted outside the 15-minute window should be considered invalid and must be repeated.

4. Interpretation of results

Positive: * Two colored lines appear. A colored line should always appear in the control line area (C) and another prominent colored line should be adjacent in the test area (T).

*Note: The color intensity of the test line area may vary depending on the concentration of SARS-CoV-2 antigen present in the sample. Therefore, any shade of color in the test line area should be considered a positive.

 Negative: A colored line appears in the control line area (C). No lines appear in the test area (T).

Invalid: The control line failed to appear. Insufficient sample size or incorrect procedure technique are the most likely causes of control line failure. Review the program and repeat the test with the new test. If the problem persists, stop using the test kit immediately and contact your local dealer.

Novel coronavirus (sars-cov-2) antigen detection kit CE

Novel coronavirus (sars-cov-2) antigen detection kit CE

一、 Product features:

1.High-quality monoclonal paired antibodies with high affinity, using double antibody sandwich method.

2.High total coincidence rate, not affected by virus mutation,no cross-reaction with common respiratory viruses.

3.Non-invasive sampling, sample type: oropharyngeal swab, sputum (saliva), testing anytime, anywhere. 

4.Storage temperature: 4℃-30℃, convenient for transportation at room temperature. 

5.Detection time 15-20 minutes.

6.Convenient operation, no equipment, no cold chain transportation.

7.Can be used for home testing, testing at designated institutions (such as hospitals), screening before the resumption of work or school.  

二、 Product usage:

三、 Interpretation of results

四、 What is the difference between nucleic acid detection, antibody detection and antigen detection of novel coronavirus?

1. Nucleic acid detection of novel coronavirus

Nucleic acid detection has the characteristics of early diagnosis, high sensitivity and specificity. It is the “gold standard” for the diagnosis of covid-19. At present, the most widely used is real-time fluorescent quantitative RT-PCR. Generally, two targets located on orf1ab and N genes are detected. The same sample must meet the requirements of double target positive or repeated detection as single target positive or both samples meet the requirements of single target at the same time to confirm sars-cov-2 virus nucleic acid positive

 2，Detection of serum antibody to novel coronavirus

  Seven days after the onset of novel coronavirus pneumonia, serum specific antibodies were gradually produced, first immunoglobulin IgM antibody, and then IgG antibody. Therefore, the increase of IgM antibody indicates recent acute infection, and the increase of IgG antibody indicates previous infection.

   The biggest advantage of serological testing is that it is convenient and fast, and the testing time is short. It can effectively break through the restrictions of existing testing technology on personnel and places, and shorten the testing time. It has been written into the diagnosis and treatment plan for novel coronavirus pneumonia (trial version     7). If the serum specific IgM and IgG antibodies of suspected cases are positive,   the     IgG antibody changes from negative to positive, or the recovery period is 4 times or more higher than that in the acute phase, they can be diagnosed as infected withnovel coronavirus. 

Interpretation of the results of combined detection of nucleic acid, IgG and IgM antibodies

3. Detection of antigen of novel coronavirus

Covid-19 antigen detection can directly detect whether human samples contain novel coronavirus. The diagnosis is fast, accurate and requires low equipment and personnel. Using double antibody sandwich method and using two antigen-specific antibodies to recognize and combine different epitopes of a target antigen can greatly reduce the probability of cross reaction and effectively improve its specificity.

4. Joint detection

The nucleic acid / antibody / antigen detection of novel coronavirus has its own emphasis and cannot be replaced each other. A variety of detection methods are applied together to complement each other. By combining molecular biology and immune level detection, we can give full play to their respective advantages, improve sensitivity and specificity, effectively shorten the detection window, improve the positive detection rate, and provide double protection for all possible risk groups