The Singapore government has recently announced that COVID-19 self-test kits are now available to the general public for purchase at retail pharmacies. This mode of testing complements the current testing methods and safe management measures put in place, including wearing of the appropriate masks.
Read on to find out more about the current COVID-19 testing methods and what these self-testing kits are.
Current Testing Methods for COVID-19
Molecular Tests (PCR Tests)
Polymerase chain reaction (PCR) tests detect genetic material of the coronavirus. This mode of testing remains the gold standard for COVID-19 testing. These tests take up to 48 hours for results to be complete as samples must be tested at laboratories.
Antigen tests are immunoassay tests used to detect specific proteins on the surface of a virus and are commonly used to diagnose respiratory pathogens. They are performed on nasal swab specimens placed in the assay’s extraction buffer or reagent.
Antibody tests detect antibodies produced by the body’s immune system in response to a previous COVID-19 infection. A blood sample is taken to detect the body’s immune response to the virus after an infection.
Since antibodies take days or up to weeks to develop after an infection and can remain in the blood after recovery, antibody tests are not used for the diagnosis of an active COVID-19 infection. Results should also not be used as an indication of a specific level of immunity or protection from SARS-COV-2, even after vaccination.
Nucleic acid amplification tests (NAATs)
NAATs detect the presence of viral nucleic acids. NAATs can remain positive up to months after the first infection and can detect viral nucleic acid when virus is unable to be cultured, meaning that the presence of viral nucleic acids does not indicate contagiousness.
What are Antigen Rapid Test (ART) self-test kits?
Antigen Rapid Test Kits (ARTs) are single-use, visually read rapid antigen tests (immunoassays) that use human nasal swab specimens for qualitative detection of the coronavirus viral protein, namely, the SARS-COV-2 antigen. They enable self-testing to aid in diagnosis of an active infection.
The different kits typically contain:
- A test device/ test strip
- Tube and buffer solution
- Nasal swab
These tests can produce results in 15-20 minutes and work best in the early stages of infection where viral load is high. The current test kits available on the market include:
- Abbott PanBio COVID-19 Antigen Self-test kit
- QuickVue At-home OTC Covid-19 Test
- SD Biosensor SARS-COV-2 Antigen Self-test Nasal
- SD Biosensor Standard Q Covid-19 Antigen Home Test
How to use ART self-test kits?
Instructions on how to use each kit differ across brands, and those who intend to use the kits are strongly advised to follow the specific instruction leaflet that comes with the purchased kit. The following provides a general guide to using the kits:
- Conduct test in a well-ventilated room away from others.
- Disinfect and dry hands before starting.
- Remove swab from the wrapper without touching the head of the swab.
- Swab both nostrils with the same swab. Insert the swab about 2cm into the back of each nostril until resistance is met and swab 4-5 times in a circular motion.
- Immediately place the swab into the liquid inside the tube and remove it after the stipulated time indicated on the leaflet.
- Perform the rest of the test according to the leaflet (testing devices are different according to kit purchased). Pay special attention to timings stated.
- Compare results with test examples in the leaflet.
- If you have a positive result, take a photo of your result together with your identification document (NRIC/passport). Then proceed to a clinic for confirmatory PCR testing and self-isolate until a negative PCR test result is received.
- If you have an invalid test result, perform a 2nd test immediately. If you have 2 invalid test results, follow the instructions for positive test result above.
- Dispose the test kit. Bag all used items in the test kit in a sealable bag and place this sealed bag into another plastic bag, then secure this with rubber band or cable tie before discarding.
Benefits of self-test kits
Rapid turnaround time enables quick detection of infected cases
ARTs can produce results in less than 20 minutes. This can help to identify those infected quickly so that medical attention can be sought faster, and isolation initiated sooner, limiting spread to the community.
This may be especially useful for pre-event testing, to reduce chances of an infected person entering the venue. By enabling rapid pre-event screening, it may potentially allow for more mass activities (e.g. weddings and religious gatherings) to be gradually resumed.
Greater accessibility to testing
For those who are asymptomatic but are concerned about infection because they may have been exposed to COVID-19 cases, ART kits offer a flexible alternative to a visit to the clinic. Furthermore, some people may wish to avoid going to the doctor’s unnecessarily for fear of coming into contact with people who have COVID-19.
For the elderly or those who are not as mobile, ART kits also offer convenience as they can just take the test at home instead of making a trip to the clinic.
Pitfalls of self-test kits
Lower sensitivity can result in false negatives
Sensitivity refers to a test’s ability to identify those infected as positive. In general, ARTs can achieve a sensitivity of about 80% for cases with higher viral loads.
With a lower sensitivity than “gold standard” PCR tests which detect the genetic material of the virus, there is a higher chance of false negative results with ART.
False negatives are negative test results even though a person is infected. It may result from:
- Poor sample preparation
- Insufficient nasal sample on swab
- Low viral protein loads in samples where the body has just been exposed to the virus.
This could lead to some cases slipping through the cracks.
ARTs can achieve high specificity of ~97 to 100% (i.e. only ≤3% of healthy subjects are false positives). False positives are positive test results even though a person is not infected.
It is important to follow instructions closely when utilising these kits to obtain accurate results.
Delay in seeking medical attention
DIY test kits are purposed for those who do not have acute respiratory infection symptoms but are concerned that they may have been exposed to Covid-19. Individuals with acute respiratory infection symptoms should visit a doctor for a full diagnosis and polymerase chain reaction (PCR) test instead.
With the easy access to ART kits however, patients with actual symptoms may choose to perform these DIY tests rather than seek immediate and appropriate medical attention. This is especially so for those who may have apprehensions about the potentially disruptive repercussions of being quarantined or losing their jobs, should they test positive officially.
Concluding thoughts on ART self-test kits
Despite its drawbacks, ART self-test kits complement the overall surveillance and safe management strategies in reducing COVID-19 transmission. As COVID-19 evolves from pandemic to endemic, quick, accessible and cheap testing looks to be the way forward in coping with the new normal of living with the virus in our midst.