Public Education on Rapid Antigen Tests for COVID-19

Rapid antigen tests cannot replace the nucleic acid test which is at present the gold standard for diagnosis of COVID-19. Notwithstanding its limitations, rapid antigen tests may play a role in facilitating access to testing and earlier detection in some people.

However, rapid antigen tests are known to have below limitations:

• Rapid antigen tests have lower sensitivity as compared with nucleic acid tests. Users should interpret the clinical sensitivity of a rapid antigen test carefully^*.
• People infected with COVID-19 may test negative during the early or late stage of infection as the viral load in these periods may be below the testing limit of the rapid antigen test.
• A false negative result may be obtained when the level of antigen in the sample is below the detection limit of the test, when sample type / collection is improper, or when the test is incorrectly performed.
• Like many other viruses, SARS-CoV-2 may mutate over time. The ability of rapid antigen test for detecting variants may vary. The performance of rapid antigen test may have to be evaluated from time to time to face the challenge of emergence of new variant.
• A false positive result may be obtained when other similar viruses co-exist in the sample, or when cross-contamination among samples occurs.
• The chance of having false positive result will be higher when the COVID-19 prevalence rate is low.

Users should pay attention to and follow the instructions from the manufacturer to perform the test and read the test result properly. Not following the instructions may generate invalid result. If in doubt, please seek advice from healthcare professionals.

Rapid antigen tests are safe if handled and used according to the instruction from manufacturer. However, chemicals contained in the solutions used in the test kits may be harmful if swallowed or absorbed inadvertently. Users should follow the instructions for use, including methods of use and disposal. Do not swallow the solutions and avoid eyes and skins contact. For accidental spillage, rinse with water. Wash hands thoroughly after using the rapid antigen tests. Tests on children should be performed with adult assistance. Test kits should be kept away from children and pets.

For those undergoing self-use rapid antigen tests:

• Positive results: Due to relatively high infection risk in the community, rapid antigen tests' positive results are relatively certain. Users tested positive by rapid antigen tests should be considered positive cases and they should take all necessary steps to avoid further spreading of the virus.
• Negative results: Users with negative result should remain vigilant, maintain all personal protection measures. Persons with symptoms or high exposure risk should continue to be tested repeatedly within a short period of time and closely monitor their health conditions.

Please refer to the following websites for more information:

• Centre for Health Protection – Q&As on Rapid Antigen Test for COVID-19
• Infographic – Learn more about COVID-19 Rapid Antigen Test
• Pamphlet – Performance of Rapid Antigen Test for COVID-19