COVID-19 diagnosis


October 23, 2021

Coronavirus Infectious Disease-19 Diagnosis (-診斷) diagnoses whether SARS-CoV-2 is detected by taking a sample and analyzing it. Two main ones detect the presence of antibodies produced in response to a virus or infection. Diagnosis of whether the virus is present in the body is used to enable health authorities to track and contain outbreaks. Antibody tests show whether or not the person being tested has COVID-19, but antibodies are not produced for several weeks after infection, so it is not useful at this point in diagnosing whether the person is infected. Diagnosis is used to assess the prevalence of disease and allows to estimate the number of people who have died from infection. Analysis of diagnostic samples and determination of infection is performed in a medical laboratory by a medical laboratory scientist using an automated analyzer. Alternatively, an infection can be detected immediately on the spot or at the doctor's office.

Specimens collection/preservation/transport


Specimens of the upper respiratory tract (nose, mouth, airways, etc.) and lower respiratory tract (lungs) are collected. The medical staff puts the sample of the lower respiratory tract (sputum) in a separate container while wearing personal protective equipment, and inserts a long, flexible cotton swab into the nasal passage for the upper respiratory tract and collects secretions such as runny nose from the back wall of the nose. If there is an agreement between the client and the laboratory in advance, the serum is collected. According to the 「Coronavirus Infectious Disease-19 Confirmation Test Guide」 of the Central Quarantine Countermeasures Headquarters, the types, doses, and containers of each specimen are as follows.

Preservation and Transport

It is best to store all samples in a refrigerated state (2-8℃) immediately after collection and transport them to the laboratory as soon as possible. However, if the sample cannot be transported or cultured immediately, it is stored or transported in a preservative solution (eg buffered glycerol saline), Cary & Blair, or transport medium. Viruses are stored and transported in Virus Trasport Media (VTM). According to the 『2019 Novel Coronavirus Laboratory Diagnostic Guidelines』, sample containers, transport conditions, and storage institutions are as follows.


Virus diagnostic tests include cell culture, antigen-antibody test, and molecular test.

Cell Culture Assay

It takes a long time for inspection and has disadvantages in that it is not suitable for large-scale inspection. It's good for isolating the virus and using it for other tasks. Conventional diagnostic tests are evaluated as inappropriate and dangerous.

Antigen/Antibody Test Method

It is a method of testing antigen (virus) or checking antibodies that are formed after the new corona 19 virus enters the body. It usually takes about 2 to 4 weeks for the body to develop antibodies to a specific infectious disease, so it is difficult to determine whether or not 'COVID-19' is confirmed at the initial stage of infection. However, it has the advantage of being able to check whether asymptomatic (unaware) confirmed cases or antibody formation after 'negative' conversion is made. In China, it is known that the antibody test method is being used as an auxiliary means to the existing test method.

Molecular Testing

In molecular diagnostics, a test target is synthesized and tested using a gene sequence (sequence).

Pancorona PCR test and sequencing

First, DNA amplification technology using PCR test is a technology that replicates a very small amount of DNA and amplifies it as much as desired for the purpose of obtaining a sufficient sample of a specific DNA sequence that can be used for analysis. Since the DNA of a specific part is doubled with each process, for example, more than 1 billion DNA can be obtained from one DNA molecule just 30 times.

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