There are generally two ways to detect the virus of Covid-19, nucleic acid detection and antibody detection. But we generally make nucleic acid testing, and naturally ignore antibody testing. This is because antibody detection is generally used as a supplementary detection indicator for suspected cases with negative nucleic acid detection for the Covid-19 or in conjunction with nucleic acid detection in the diagnosis of suspected cases. It cannot be used as a basis for diagnosis and exclusion, and is more suitable for retrospective examination. So what is the difference between the two tests? Which test is the VTM more suitable for?

VTM (Virus Transportation Media)

It is a liquid used for virus sample testing. There are mainly two types of inactivated and non-inactivated. The inactivated type can quickly inactivate the virus and release the virus’ nucleic acid for rapid nucleic acid detection.The non-inactivated type can protect the activity of virus’ RNA and protein at the same time, which can be used for virus nucleic acid detection and  antibody detection.

The differences between nucleic acid detection and antibody detection

1.Different samples

Nucleic acid detection requires respiratory samples, including pharynx, nasopharyngeal secretions, sputum, bronchi, lavage fluid, lung biopsy, etc. The collection process is very complicated.

Antibody detection is a blood test, which can be collected by peripheral blood or venous blood collection. The sample collection method is more convenient and safe, and the sample can be stored for 72 hours.

2.Different detection methods

Nucleic acid testing is a direct detection of viruses. It takes the specific DNA sequence of the virus as the detection target.Through PCR amplification, the target DNA sequence we chosen increases exponentially. Each amplified DNA sequence can be combined with a pre-added fluorescent marker. The probes bind, producing a fluorescent signal. The more target DNA amplified, the stronger the accumulated fluorescent signal. In samples without virus, no increase in fluorescence signal was detected because there was no amplification of the target DNA. Moreover, the nucleic acid sample has harsh storage conditions, RNA is easily lysed, and can only be stored for 24 hours at 4°C.

Antibody testing is an indirect test. It is not directed against the virus itself, but a specific antibody produced by the immune response of the human body after infection with the virus . The human body gradually produces antibodies about a week after being infected with the virus and then rises rapidly. The human body generally produces antibodies called IgM first. A positive IgM antibody indicates a recent infection, and a positive IgG antibody indicates a long period of infection or previous infection.

3.Different detection conditions

Nucleic acid testing requires specialized instruments and standard molecular testing laboratories. PCR certification personnel required to operate. The steps are cumbersome and the whole process takes 5 to 8 hours. The risk of contamination during the process is high.

Antibody detection breaks through the limitations of existing nucleic acid detection methods on personnel and places. It can be detected in large quantities quickly, and can be completed in primary laboratories with low risk of contamination.

It can be seen from above there are advantages and disadvantages for no matter what kind of Covid-19 virus detection method is used. Antibody detection is a supplement to the false negative of nucleic acid detection. The combination of the two can effectively improve the diagnostic efficiency of the Covid-19, and has extraordinary value for epidemic prevention and control.

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