Scientists fear people will be forced to use outdated Covid tests to save on living costs this Christmas.
However, they warn that this may be false economics, since one cannot be sure that “negative means negative.”
It’s been almost two years since the government ended free testing in April 2022, meaning even the latest tests released will soon expire, which usually happens in 24 months or less.
And as the new JN.1 subvariant continues to spread rapidly across the UK, scientists are urging people to stop using expired Covid tests in the coming days and weeks as the government’s latest free tests come to an end.
“I suspect that many people had lateral flow kits available when they were freely available. Most of them are already outdated.
“Given the cost of lateral flow kits and the current cost of living crisis, it is very likely that people are using these old and inaccurate tests,” Professor Lawrence Young, a virologist at the University of Warwick, told me. I.
“It is important that people check the expiration date of their lateral flow kits as outdated tests are unreliable. This means you can’t be sure that a negative test result means you really don’t have Covid.
“The test materials in the kit deteriorate over time and this can affect performance and results. This is especially problematic with a buffer solution, which typically lasts a maximum of two years. The buffer liquid evaporates over time and this affects the effectiveness of the test.
“So if the lateral flow kit was purchased some time ago, when you try to spray the test strip, there may not be enough liquid remaining on the test strip, and the strip itself may also be damaged. “It is much better to buy a new lateral flow kit so you can be confident in the outcome and be more confident that you are not spreading the infection to more vulnerable family members and friends,” Professor Young said.
The end of free testing, as well as the overall decline in Covid cases and severity, means fewer and fewer people have been tested for the virus this year.
However, according to the UK’s Health Security Agency, cases are starting to rise again after weeks of relatively low levels, with “Covid-19 activity increasing in most regions, ethnicities and age groups”.
Most worryingly, hospital admissions for Covid-19 rose to 3.80 per 100,000, up from 2.96 per 100,000 the week before.
Meanwhile, the World Health Organization on Tuesday classified the JN.1 Omicron subvariant circulating in the UK and around the world as a “variant of concern”, meaning it should be a priority for close monitoring and research around the world.
The WHO said there has been a rapid rise in infections, which is likely to lead to an overall rise in Covid cases.
However, it said that “the limited data available do not suggest that the severity of comorbidity is greater compared with other circulating variants.”
In the UK, JN.1 accounted for 28 percent of Covid cases on December 11, up from 7.5 percent just a month earlier, four times the proportion of new infections during that period.
And with more indoor socializing over the Christmas period expected to lead to an even higher rise in Covid cases, people are more likely to reach into the cupboard for an old test left over from the start of the pandemic, which may well have expired and may not be effective , scientists warn.
In some cases, they may not realize that the test has expired, and in other cases, they may be tempted to assume that the test is still effective even if they see that it is, the scientists say.
Professor Nam Tran of the University of California, Davis compares the tests to food and asks, “Would you drink milk that was past its expiration date months ago?”
While home testing kits don’t deteriorate in the same way as milk, the chemicals, ingredients and packaging can “degrade,” meaning they actually deteriorate, he notes.
“The risk is that you get a false negative result and then spread the disease. Alternatively, a false positive result could prevent you from going to work or other activities,” Professor Tran said.
He explained that most home Covid test kits are “lateral flow” tests.
“They often use antibodies produced by manufacturers to capture proteins of interest, such as SARS-CoV-2 proteins, and detect the virus.”
The kits also include a liquid solution that can destroy the virus.
“In some tests, this helps kill the virus and release viral proteins needed for detection. This solution also helps move the protein along the test strip so the tests can detect unique antibodies,” he said.
He explained that the test could produce unreliable results if any one of these components fails as the kit ages.
“The chemicals can go bad. Antibodies used to detect the virus can be destroyed by time, heat and air. Moisture entering the test kit can, among other things, damage the paper strip,” said Professor Tran.
But Professor Steve Griffin, a virologist at the University of Leeds, said that while using outdated kits is “not ideal”, there may be cases where expired tests will still work as effectively as before after their expiration date.
“Of course, many of the tests provided by the government expire in January 2024, many of which I have myself,” he said.
According to him, shelf life depends primarily on the life of the liquid in the sample processing tubes.
“So if you notice that the liquid has evaporated, become cloudy or changed color, there is a good chance the test will not work. If the liquid remains clear and has the same volume as when you purchased the kit, there should be no problems with the test in the near future.
“This is because other important ingredients are not only stable in nature, but are also preserved through freeze-drying (drying into powder) in the device.
“If you suspect they have been damaged or exposed to high/cold temperatures, chemicals or even water, then there certainly may be good reason to doubt the integrity of the sealant,” he warned.
Source: I News
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