SINGAPORE – Demand for antigen rapid test (ART) kits has surged in recent weeks as the number of Covid-19 cases in Singapore hit a record high for 2023.
Checks by The Straits Times on Dec 6 found several pharmacies and stores had run out of ART kits, and shelves remained bare the day after.
On Dec 11, the Ministry of Health (MOH) said retailers and pharmacies have sufficient supply and have placed fresh orders to meet the spike in demand.
The Straits Times spoke to experts to find out whether people can continue to safely use ART kits and masks even if they are expired, and whether the kits will still be effective when testing for the latest Covid-19 variants.
Q: What is the shelf life of ART kits and masks?
A: The United States Food and Drug Administration (FDA), which approves ART kits, has said the shelf life of these kits are between four and six months from the date of manufacture.
However, shelf life can be longer than the given expiry date found on the packaging if the manufacturer finds that test results are more stable. In that case, manufacturers can ask FDA to give test kits a longer shelf life.
To check if the expiry date of an ART kit has been extended, go to this website.
Unlike ART kits, the shelf life of masks, and likelihood of extending their expiry dates, is unclear, said Professor Paul Tambyah, an expert in infectious diseases at the National University of Singapore (NUS) Yong Loo Lin School of Medicine.
He said: “Unfortunately, there are so many mask manufacturers that there is no equivalent of the FDA website listing on extended expiry dates for masks.”
Prof Tambyah said people can refer to the expiry dates found on the mask packaging as well as the instructions on how best to store them.
Q: Can I still use expired ART kits and masks?
A: No, expired ART kits can give inaccurate results while expired masks provide less protection against Covid-19, said health experts.
Prof Tambyah said misleading results like false positives and false negatives can arise from the degradation of the chemicals in the test solutions.
ART tests work by identifying the viral antigen – usually the nucleocapsid (N) protein of Sars-CoV-2, which is the virus that causes Covid-19. The antigens bind to antibodies, resulting in a line on a test strip.
If the antibodies have degraded, the test kit may not be able to detect the viral proteins, even indicate if the protein is not there, added Prof Tambyah.
As for expired masks, the fabric is likely to degrade over time, forming micro tears invisible to the eye, said Associate Professor Richard Sugrue, who specialises in molecular and cellular virology at the Nanyang Technological University School of Biological Sciences.
He said: “If someone with Covid-19 coughs out droplets of saliva towards you, the droplets would land on the surface of your mask and it is unlikely you will inhale it.
“But, if there are tears in your mask, the droplets can get in and infect you.”