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  • The SARS-CoV-2 is an emerging virus responsible for the respiratory illness Coronavirus Disease 2019

  • When a person is exposed to a new virus

  • and after an incubation period

  • the immune system creates proteins called antibodies

  • as part of the body’s natural response to fight the infection and to neutralize the pathogen

  • Antibodies can come in different varieties known as isotypes or classes

  • IgM antibodies are produced against the viral antigen in the early stages of infection

  • and are detectable after four to seven days after symptoms develop

  • Following that, IgG antibodies are produced seven to 14 days after the onset of symptoms

  • and are detectable for months and even years

  • depending upon the antigen and the individual

  • These antibodies can also be detected if a person has an infection without any symptoms

  • The COVID-19 antibody test is used to detect the presence of the anti-SARS-CoV-2 IgM and IgG antibodies

  • in human whole blood, serum, or plasma samples

  • by using a cassette-based systems

  • To perform a test, the cassette is placed on a level surface at room temperature

  • then one of the fingers is punctured with a lancet

  • and a plastic dropper is used to take several drops of blood

  • then one drop is added into the cassette sample well

  • Finally, drops of a buffer are added into the sample well to facilitate the test

  • and the cassette is incubated for 10 minutes

  • The test Kit is a qualitative lateral flow immunochromatographic assay

  • and the test device contains

  • a sample pad, where the combined sample flows down

  • A conjugation pad, which contains Gold - Covid-19 antigen conjugate

  • the antigen will bind to the anti-SARS-CoV-2 antibodies in the sample

  • and two different antigens can be used

  • one with affinity to IgM and a second with affinity to IgG antibodies

  • The virus antigen is labelled with gold nanoparticles

  • which can be used as visual indicator

  • because of the nanoparticle’s interactions with visible light

  • So that, the Gold nanoparticles absorb and scatter light

  • resulting in a red color

  • In addition, rabbit IgG antibodies labeled with gold nanoparticles exist in the conjugation pad

  • and they are used for quality control to assess test validity

  • the test strip also contains a nitrocellulose membrane with three lines

  • first line coated with anti-human IgM antibodies

  • second line coated with anti-human IgG antibodies

  • and third line coated with Anti-Rabbit IgG Antibodies

  • In addition, an absorption pad is used in the test strip to move the sample across the test

  • The sample migrates laterally across the membrane by capillary action.

  • During testing, the antibodies in the sample

  • react with the SARS-CoV-2 antigen, and its conjugate gold nanoparticles

  • in the conjugation pad

  • The mixture then migrates laterally across the membrane by capillary action

  • and the IgM and IgG antibodies are bound

  • to the anti-human IgM and anti-human IgG antibodies, respectively

  • While, the rabbit IgG antibodies are bound to the Anti-Rabbit IgG Antibodies

  • Only those conjugated with COVID-19 antigen-gold nanoparticle complexes

  • will produce a visible colored line

  • The test result is positive

  • if both IgM and IgG antibodies are detected

  • if only IgM antibodies are present

  • and if only IgG antibodies are detected

  • When IgM is Positive and IgG is Negative

  • the subject’s immune system is actively producing antibodies

  • to a recent infection with the target virus

  • When Both IgM and IgG are Positive

  • the subject’s immune system is actively producing antibodies

  • to an ongoing infection that likely began more than 14 days ago

  • When IgG is Positive and IgM is Negative

  • the subject’s immune system has produced antibodies to the target viral antigen

  • A negative test result means that the person is not infected with the virus

  • or perhaps the person has a recent infection but the antibodies are not yet produced

  • Also, since the accuracy of the test depends on the amount of the antibodies

  • some people may not develop detectable antibodies after an infection

  • Because COVID-19 is a new disease

  • we don’t know exactly how long antibodies last

  • so a negative test could mean that the person has been infected in the past

  • and the antibodies are no longer detectable

  • The test result is invalid

  • if the quality control line C does not show a red color

  • therefore the sample must be retested

The SARS-CoV-2 is an emerging virus responsible for the respiratory illness Coronavirus Disease 2019

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冠狀病毒抗體測試-動畫視頻(Coronavirus Antibody Test - Animated Video)

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    1 23 發佈於 2022 年 11 月 22 日
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