How to tell if your ART test kit has expired and if you can still use it

f your household has received the latest batch of six antigen rapid test (ART) kits from the government recently, you might be wondering: What do I do with them when you have a stockpile of test kits in your drawer – and no one at home has come down with COVID-19 lately?

Or you might have other queries such as, “can I still use the test kits from two years ago?”, “how do I tell if the test kits have gone bad?” and “can I donate them?”. We find out from the experts:

CAN I STILL USE THE ART TEST KIT FROM TWO YEARS AGO?

To be certain, check the expiration date stamped on the box. Make sure you’re looking at the “expiration date” because the “shelf life” is something else altogether.

The shelf life is how long the test kit should perform as expected and is measured from the date of manufacture, according to the US Food and Drug Administration (FDA). On the other hand, the expiration date is set at the end of the shelf life and is the date through which the test is expected to perform as accurately as when manufactured.

The majority of ART kits sold in Singapore expire between two and three years from the date of manufacture, according to the Pharmaceutical Society of Singapore (PSS).

As for the shelf life of most kits marketed in Singapore, they are usually between 15 and 24 months, said Professor Paul Tambyah, a senior consultant with Division of Infectious Diseases, Department of Medicine, National University Hospital.

WHAT IF THE TEST KIT IS JUST ONE OR TWO DAYS PAST ITS EXPIRATION DATE? CAN I STILL USE IT?

You could check the updated expiration dates of your test kit on the FDA website, said Prof Tambyah, as “some of the manufacturers and regulatory authorities have extended the expiry dates of some kits”. However, “this applies to some but not all test kits”, he said.

The expiration dates provided by manufacturers tend to be conservative, said Dr Jaichandar KS from the Biomedical Engineering Technical Committee with The Institution of Engineers, Singapore, but the dates aren’t to be taken lightly as they are “based on stability testing conducted during product development”.

“It is important to exercise caution and follow established guidelines when considering the use of test kits beyond their printed expiration date,” he said.

ARE THERE CERTAIN STORAGE CONDITIONS I SHOULD KEEP THE TEST KITS IN?

To maintain the effectiveness of the ART kits, appropriate storage conditions should be observed, said Dr Jaichandar. First, you’ll want to keep your test kits in a cool place with a temperature between 15 degrees Celsius and 30 degrees Celsius, he said. You’ll need a “dry environment with moderate humidity levels” and “avoid direct sunlight and excessive exposure to light”.

The ART kits are also not things you want to tamper with, like opening and transferring them into more aesthetically pleasing containers. “The individual packaging and pouches of each of the test components must not be tampered with, broken or opened until immediately before the test is to be conducted,” said Kng Li Lin, Grace, a community pharmacist and member of the PSS.

“Exposing the test components to light, moisture and oxygen for a prolonged period may affect the accuracy of test results,” she said.

As for ART kits kept in the fridge, “all kit components must be brought to room temperature for a minimum of 30 minutes prior to use”, said Law Hwa Lin, a senior principal pharmacist (specialist) and member of the PSS.

If you’re wondering, should you keep all your test kits in the fridge, Prof Tambyah said that “it depends on the test kit and the respective manufacturers’ instructions”.

“Appropriate storage generally refers primarily to room temperature and the FDA has suggested 15 degrees Celsius and 30 degrees Celsius, which is around the room temperature in Singapore in both air-conditioned and non-air-conditioned settings.”

DO EXPIRED TEST KITS SHOW PHYSICAL CHANGES IN THE SOLUTION OR TEST STRIP?

“Expired ART kits may exhibit various physical changes, which can serve as indicators of potential degradation or loss of effectiveness,” said Dr Jaichandar.

Some of the common signs can include colour changes in the liquid reagent or buffer solution. “For example, it might become discoloured, turn cloudy or show signs of contamination. Any noticeable change in colour can be a warning sign that the kit has expired,” he said.

Dr Jaichandar added: “This is a specific antibody or antigen used to detect the target pathogen, such as a virus or bacterium. Over time, the reactivity of these reagents can decrease, resulting in reduced sensitivity.”

Also, look out for changes in the test strip’s appearance as they may indicate expiration. “The test strip or membrane within the test cassette may change colour or become discoloured,” said Dr Jaichandar.

“The test strip contains the membrane where the test and control lines are located. It is coated with capture antibodies or antigens that react with the target pathogen. Any changes in the integrity or functionality of this strip can impact the test results,” he said.

WHAT ABOUT THE RESULTS OF EXPIRED TEST KITS? WHAT ARE THEY LIKELY TO SHOW?

“It is hard to say but I think false negatives are theoretically more likely,” said Prof Tambyah. “That is because a working buffer is essential to make sure the sample travels up the test strip to get the results. If the sample cannot travel up the strip, it might appear negative when there actually is virus in the swab.”

Kng added that “there is no guarantee how the deterioration may affect the test results”. It is always better to err on the side of caution and “always follow the expiry date stated by the manufacturer of the ART test kits”, said Law, because there is no guarantee that “using an expired ART test kit would produce accurate results”.

How many ART kits to keep depends on your “anxiety level and the number of immunocompromised people at home”, said Prof Tambyah. “For those who are vulnerable or at risk of severe infections, more test kits are needed so they can seek medical attention early. For the rest of us, I think one kit per person is more than enough.”

For a family of four, Dr Jaichandar suggested as a general guideline to have a minimum of four to eight test kits. But ultimately, “the number can depend on various factors, including the prevalence of COVID-19 in your area, the frequency of potential exposure and your individual circumstances”, he said.

As for donating your surplus test kits, you can check with the free clinics that serve the needy in Singapore and donate your kits to them, said Prof Tambyah.

Alternatively, approach local charities, non-profit organisations or community groups, said Dr Jaichandar, which “may be actively seeking donations of test kits for distribution to vulnerable populations or individuals who cannot afford them”.

“Consider posting your intent to donate test kits on social media platforms or community groups. There may be individuals or families in your local area who would appreciate your generosity,” said Dr Jaichandar.

Before you do that, “it’s essential to ensure that the test kits you are donating are unexpired, in good condition and have not been tampered with to guarantee their effectiveness”, he reminded.