The COVID-19 Antigen Rapid Test Kit is a medical testing tool used for quickly detecting the antigens of the novel coronavirus (SARS-CoV-2).

1. Structural Components

• Test Strip:
  This is the core part of the test kit. The test strip is usually a small plastic card that contains a test line and a control line inside. The test line is used to bind to the COVID-19 antigens in the sample. If antigens are present in the sample, the test line will develop color through the antigen-antibody reaction. The control line is used to verify whether the testing process is valid. Regardless of whether there are antigens in the sample or not, the control line should develop color. For example, during use, if the control line does not develop color, the test result is invalid and the test needs to be repeated.
• Sampling Swab:
  It is used to collect samples from the nasal or throat areas. The swab is generally made of materials such as polyester fiber or cotton, with a soft tip that can reduce irritation to the sampling site. Its design allows it to go deep into the nasal cavity or throat to effectively obtain mucosal cells containing viral antigens. For example, when taking a nasal sample, the swab needs to go about 1 – 2 centimeters deep into the nasal cavity and rotate several times along the nasal wall to collect a sufficient sample.
• Sample Extraction Buffer:
  The main component is a buffer solution, and its role is to extract viral antigens from the collected samples and provide a suitable reaction environment for the subsequent antigen-antibody reaction. The sample extraction buffer can lyse the virus to release the antigens while maintaining the stability of the antigens. Generally speaking, the amount of the extraction buffer is precisely designed, usually several milliliters, to ensure that the collected samples can be fully processed.

2. Detection Principle

It is based on the specific binding reaction between antigens and antibodies. The detection reagents in the test kit contain antibodies specific to the specific antigens of the novel coronavirus. When the collected samples (such as nasal or throat swab samples) are processed, the viral antigens in them will bind to the antibodies in the detection reagents. If there is a sufficient amount of antigens in the sample, this binding will trigger a series of signal amplification reactions, which will eventually lead to the color development of the test line. The test results are judged by visually observing the color development of the test line and the control line. For example, if both the test line and the control line develop color, the result is positive; if only the control line develops color, the result is negative; if the control line does not develop color, the test result is invalid.

3. Application Scenarios

• Home Self-testing:
  It is convenient for individuals to quickly conduct tests at home when they have suspected COVID-19 symptoms (such as fever, cough, sore throat, etc.). This self-testing method can timely detect possible infection situations and provide a reference for individuals to take subsequent actions such as isolation measures and seeking medical treatment. For example, if a person feels that he or she has mild fever and cough symptoms and uses the antigen rapid test kit to conduct a test at home, if the result is positive, he or she can immediately isolate himself or herself to avoid infecting family members and contact medical institutions in time for further confirmation and treatment.
• Rapid Screening in Medical Institutions:
  In the entrances of hospitals, clinics and other medical institutions or in fever clinics, the antigen rapid test kits can be used to conduct preliminary screening on a large number of patients. This rapid testing can distinguish possible positive patients within a short time and provide a basis for medical institutions to reasonably arrange testing resources (such as nucleic acid testing) and 分流 patients. For example, during the peak of the epidemic, patients with symptoms were first subjected to antigen rapid testing. Positive patients were given priority for nucleic acid testing and isolation treatment, while negative patients could be diagnosed and treated according to the routine process, which improved medical efficiency.
• Testing in Collective Places such as Schools and Enterprises:
  It can be used for regular or irregular large-scale testing in crowded places such as schools, enterprises, and large event venues. This helps to timely detect potential sources of infection and prevent the spread of the virus in the collective environment. For example, schools can conduct antigen testing on all teachers and students at the beginning of the school term or test close contacts after the appearance of suspected cases to ensure the safety of the campus environment.