COVID-19 Rapid Antigen Tests

Products

Rapid antigen tests for the detection of SARS-CoV-2 are available as medical devices from various suppliers (e.g., Roche, Abbott) for use by health care professionals. They are not approved for self-testing by patients in many countries. The rapid tests can be performed, for example, in doctors’ offices, hospitals, test centers, laboratories and pharmacies with suitable infrastructure and an appropriate safety concept. In many countries, the tests will be released from November 2, 2020.

Mode of action

The rapid test is based on the detection of antigens of SARS-CoV-2 using specific antibodies against viral proteins and a color reaction (immunochromatography, immunoassay). In contrast to the PCR test, proteins such as the nucleocapsid protein (N) and not nucleic acids are detected. The principle is comparable to a pregnancy test.

Areas of application

For the qualitative detection of SARS-CoV-2 antigens. The test can be performed in symptomatic and asymptomatic individuals.

Implementation

The professional must wear appropriate protective equipment and the premises must be suitable. A swab from the nasopharyngeal cavity (nasopharyngeal swab) serves as the sample material. For this purpose, the sterile swab provided is inserted into the nasal opening until the surface of the posterior nasopharynx is reached. The swab is rubbed against the wall several times while being rotated and then pulled out again. The sample is mixed with a buffer solution and placed in the appropriate opening of the rapid test. The result is available quickly, within 15 to 30 minutes, depending on the test. A colored control band (C) visually indicates whether the test has worked correctly. If this is missing, the test is invalid. If coronaviruses are present in the sample material, a colored test line (T) will form and be optically detectable. Even if the line is pale, the test is considered positive. Full details can be found in the product information of the tests.

Advantages

  • The result is available very quickly.
  • No expensive laboratory equipment is required.
  • The test is relatively inexpensive and can be performed at the point of care.
  • The threshold for test performance is lower.
  • Those who test positive can go into isolation and receive treatment.

Disadvantages

Despite the high accuracy, false results can occur. Therefore, a negative result does not rule out infection. Hygiene measures must continue to be followed. The antigen test is less reliable than the PCR test, especially in terms of sensitivity. In the case of a negative result, a PCR test can also be used in case of doubt. False positive results, on the other hand, are very unlikely because of the high specificity.