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Lateral flow tests: Do LFTs detect the omicron coronavirus variant?

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Positive and negative rapid lateral flow tests

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With the omicron variant of the coronavirus on the rise, regular testing has become even more important, particularly as people decide whether to socialise during the Christmas period. Here’s everything you need to know about testing.

What is the difference between a lateral flow test and a PCR test? 

Polymerase chain reaction (PCR) tests were the first available for spotting the coronavirus. They work by detecting the virus’s genetic material, and are very accurate. Then came rapid tests, also called lateral flow tests (LFTs). Unlike PCR tests, these detect proteins from the virus, which are present when someone is infectious. Although both begin with someone taking a swab from their nose or throat, most PCR tests have to be sent to a laboratory, while rapid LFTs can be completed by the user at home and give results in minutes.

Are LFTs less good than PCRs?

Rapid tests aren’t as good as PCR tests at detecting the coronavirus because PCR tests involve a step where the genetic material is multiplied over and over again, so they can detect tiny starting amounts. LFTs have no multiplying stage, so may miss infections where virus levels are low.

Can we quantify the difference?

Various studies have put the sensitivity of LFTs – in other words, their ability to detect the virus if it is there – at about 40 to 60 per cent. That sounds unhelpfully low, but it is an unfair measure as it compares LFTs to PCR tests, which are arguably too sensitive, says Irene Petersen at University College London. In the weeks following an infection, the cells of the nose and throat can retain fragments of virus genetic material that aren’t infectious, but that can be amplified by the PCR process, leading to a positive result.

Taking this into account, modelling work by Petersen’s team suggests that a study in Liverpool that gave a sensitivity of 40 per cent for LFTs actually indicates that their accuracy is more than 80 per cent.

If rapid LFTs are unreliable, what is the point of taking one?

“Many people seem to view things as either ‘these tests work’, so if I get a negative result then I’m fine, or ‘they don’t work’, so they’re useless and I won’t bother using them, whereas the reality is something in between,” says Hayley Jones at the University of Bristol, UK.

People should use a positive result as a “red light” for stopping a social activity, but they shouldn’t use a negative result as a “green light” to go ahead with an activity that is potentially risky, as they might have some mild covid-19 symptoms, she says. “If your ‘pre-test’ decision is not to do the activity, then I would not generally recommend letting a negative result change your mind,” says Jones.

How about if there is only a faint line on an LFT?

That shows virus protein is present. “Positive lateral flow test results can show an extremely faint band, which some people might incorrectly read as a negative test result,” says Jones. “I think [that] has not been well communicated.”

Why are rapid LFTs not recommended if someone has symptoms? 

The UK government recommends that people use LFTs only if they don’t have symptoms, for regular screening or on days when they are likely to mix with other people. If anyone has symptoms, they should use the more accurate PCR tests. But in practice, many people do use LFTs if they have symptoms, especially if they are very mild or are not the “official” covid-19 symptoms.

“You can have the [virus] proteins whether you have symptoms or not,” says Petersen. “The test doesn’t know if you have symptoms.” In fact, most studies of LFTs suggest they are somewhat more accurate at detecting positive cases in people who have symptoms than in those who are symptom free.

So is it OK to use an LFT if I have symptoms?

The crucial thing to remember is that if you have covid-19 symptoms, a negative LFT doesn’t give you the all-clear: you still need to use a PCR test. But LFTs for people with symptoms can be helpful while they are waiting for a PCR result, especially if PCR tests are hard to access, as they are at the moment, says Petersen.

I’ve heard LFTs don’t detect the omicron variant, is that right?

This isn’t true. Although the omicron variant has more than 30 mutations, the antibodies used in LFTs can still bind to the viral proteins. “Initial laboratory validation… has determined similar sensitivity to detect omicron compared to delta,” the UK Health Security Agency said last week. Nevertheless, some people will get false negative results because the test’s sensitivity is relatively low.

In some reported cases of people spreading the virus after a negative LFT, they may have been genuinely negative at the time of testing and turned infectious a few hours later. “It is always possible to test negative and then go to positive,” says Al Edwards at the University of Reading, UK. Because of this, it is better to test just before mixing with other people, rather than relying on a negative test from the day before.

Will we get better rapid tests in future?

Several other kinds of rapid tests are either in development or already available. For instance, a product from a UK firm called Intelligent Fingerprinting involves taking a swab from inside the cheek, which is easier than swabbing the nose or throat. Another UK firm called Aureum Diagnostics is developing a system where people can put a saliva sample on a test strip. The strips are impregnated with the ACE-2 receptor, which the coronavirus normally binds to when entering human cells. But to be useful, any new test would have to be as cheap and easy to mass produce as LFTs, says Edwards. “Where LFTs really succeed is their scalability and [ease of] mass manufacturing.”

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Solar storms may cause up to 5500 heart-related deaths in a given year

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In an approximate 11-year cycle, the sun blasts out charged particles and magnetised plasma that can distort Earth’s magnetic field, which may disrupt our body clock and ultimately affect our heart



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17 June 2022

A solar storm

Jurik Peter/Shutterstock

Solar storms that disrupt Earth’s magnetic field may cause up to 5500 heart-related deaths in the US in a given year.

The sun goes through cycles of high and low activity that repeat approximately every 11 years. During periods of high activity, it blasts out charged particles and magnetised plasma that can distort Earth’s magnetic field.

These so-called solar storms can cause glitches in our power grids and bring down Earth-orbiting satellites. A handful of studies have also hinted that they increase the risk of …

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UK Covid infection rate rising, with more than a million cases in England | Coronavirus

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Coronavirus infections are rising in the UK, figures have revealed, with experts noting the increase is probably down to the more transmissible BA.4 and BA.5 Omicron variants.

The figures from the Office for National Statistics (ONS), based on swabs collected from randomly selected households, reveal that in the week ending 11 June an estimated one in 50 people in the community in England are thought to have had Covid – around 1.13 million people.

The figure is even higher, at one in 45, in both Wales and Northern Ireland, while it was highest in Scotland where, in the week ending 10 June, one in 30 people are thought to have been infected.

While the figures remain below the peak levels of infection seen earlier this year, when around one in 13 people in England had Covid, the findings are a rise on the previous week where one in 70 people in England were thought to be infected. Furthermore, the data reveals increases in all regions of England, except the north-east, and across all age groups.

Experts say that a key factor in the increase is probably the rise of the Covid variants of concern BA.4 and BA.5.

“Infections have increased across all four UK nations, driven by rising numbers of people infected with the BA.4 and BA.5 Omicron variants,” said Kara Steel, senior statistician for the Covid-19 Infection Survey.

While Steel said it remained too early to say if this was the start of another wave, others have warned it may already have begun, with increased mixing and travelling among other factors fuelling a rise in cases.

Among concerns scientists have raised are that BA.4, BA.5 and another variant on the rise, BA.2.12.1, replicate more efficiently in human lung cells than BA.2.

Prof Azra Ghani, an epidemiologist at Imperial College London, said the latest figures were not surprising, and might rise further.

“This increase in infection prevalence is likely due to the growth of the BA.4 and BA.5 Omicron subvariants, which as we have seen elsewhere in Europe, appear to be able to escape immunity generated from previous Omicron subvariants,” she said.

“It is therefore possible that we will continue to see some growth in infection prevalence in the coming weeks and consequently an increase in hospitalisations, although these subvariants do not currently appear to result in any significantly changed severity profile. This does however serve as a reminder that the Covid-19 pandemic is not over.”

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NHS to offer women in England drug that cuts recurrence of breast cancer | Breast cancer

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Thousands of women in England with breast cancer are to benefit from a new pill on the NHS which reduces the risk of the disease coming back.

The National Institute for Health and Care Excellence (Nice) has given the green light to abemaciclib, which cuts the chance of breast cancer returning after a patient has had surgery to remove a tumour.

Trials showed that patients who had the drug with hormone therapy had a more than 30% improved chance of their cancer not coming back after surgery, compared with hormone therapy alone.

“It’s fantastic thousands of women with this type of primary breast cancer will now have an additional treatment option available on the NHS to help further reduce the risk of the disease coming back,” said Delyth Morgan, the chief executive of charity Breast Cancer Now.

“The fear of breast cancer returning or spreading to other parts of their body and becoming incurable can cause considerable anxiety for so many women and their loved ones.

“New effective treatments such as abemaciclib, which can offer more women the chance to further reduce the risk of the disease recurring, are therefore extremely welcome and this is an important step change in the drug options available for this group of patients.”

The twice-a-day pill is suitable for women with hormone receptor-positive, HER2-negative, node-positive early breast cancer at high risk of recurrence who have had surgery. About 4,000 women will benefit initially, Nice said.

Helen Knight, the interim director of medicines evaluation at Nice, said the draft recommendation came less than a month after abemaciclib received its licence.

“The fact that we have been able to produce draft recommendations so quickly is testament to the success of our ambition to support patient access to clinically and cost effective treatments as early as possible,” said Knight. “Until now there have been no targeted treatments for people with this type of breast cancer.

“Abemaciclib with hormone therapy represents a significant improvement in how it is treated because being able to have a targeted treatment earlier after surgery will increase the chance of curing the disease and reduce the likelihood of developing incurable advanced disease.”

Abemaciclib works by targeting and inhibiting proteins in cancer cells which allow the cancer to divide and grow. It normally costs £2,950 for a packet of 56 150mg-tablets, but the manufacturer, Eli Lilly, has agreed an undisclosed discounted price for NHS England.

“Thanks in part to this latest deal struck by NHS England, NHS patients will be able to access another new targeted drug for a common and aggressive form of breast cancer,” said Prof Peter Johnson, the cancer director of NHS England.

“Abemaciclib, when used alongside a hormone therapy, offers a new, doubly targeted, treatment option, helping to increase the chances of beating the cancer for good, as well as meeting the NHS’s commitment to delivering improved cancer care under our long-term plan.”

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