Saturday , October 16 2021

Lateral flow tests detect people at higher risk of Covid spread, the study says



Lateral flow tests detect people at higher risk of Covid spread and are more accurate than previously thought, according to the study

  • The research found that lateral flow tests detect about 80% of Covid-positive cases
  • Swabs are 90% effective in detecting Covid when people are most infectious
  • Previous research underestimated its effectiveness, the researchers say










One study has stated that lateral flow tests are better at detecting people at higher risk of Covid spread and are more accurate than previously thought.

British and American researchers found that rapid tests are 90% effective in detecting the virus in people who are more infectious.

And the study found that swabs, which have been criticized for both lost cases and for producing false positives, especially when administered on their own, are up to 80% effective in finding Covid in all people.

Lateral flows are the standard tests used in UK schools and are free at the NHS for asymptomatic people.

Previous research has suggested that tests, which can yield results in as little as 15 minutes, lose up to 42% of asymptomatic people and 22% of symptomatic cases.

But most other studies compare the results of lateral flow with infections confirmed by a lab-based PCR test, which is “like comparing apples and oranges,” according to the researchers.

Instead, they used a mathematical formula to recalibrate previous data to reflect the fact that lateral flows are designed to detect people who are actively infectious and not diagnose any infection, as is the case with PCRs.

One study has stated that lateral flow tests are better at detecting people at higher risk of Covid spread and are more accurate than previously thought.

One study has stated that lateral flow tests are better at detecting people at higher risk of Covid spread and are more accurate than previously thought.

WHAT HAS THE PREVIOUS INVESTIGATION SAID ABOUT THE ACCURACY OF COVID SIDE FLOW TESTS?

Rapid coronavirus testing can lose four out of ten asymptomatic people, a major review concluded earlier in the pandemic.

Researchers who analyzed 64 studies on the effectiveness of lateral flow kits found that they could not detect 42% of cases that showed no signs of disease.

The Cochrane gold standard review found that tests, which yield results in as little as 30 minutes, were better for detecting symptomatic cases (78%).

The findings have caused concern among some scientists because at least half of Covid’s transmission is believed to come from patients who look good.

Children are even less likely to get sick with coronavirus, but they can act as spreaders of the disease.

Hundreds of thousands of side flow tests on teachers and students are used every day in order to keep Covid schools open and free. They are also deployed in nursing homes, hospitals and everywhere companies.

Professor Jon Deeks, a biostatistician at the University of Birmingham and co-author of the report, said ministers could have launched lateral flow tests in schools “without any real-world evidence”.

The review also found that lateral flow tests were prone to give false positives, when a test says someone is infected but is not.

Senior Professor Irene Petersen, an epidemiologist at University College London, said it doesn’t make much sense to use PCR tests as a “gold standard” when compared to lateral flows.

He said: “Previous studies comparing the reliability of lateral flow tests and PCR tests could be potentially misleading because a PCR test is a marker of having been infected at some point within a given period of time. and does not necessarily mean that someone is infectious when taking the tests.

“In most validation studies, individuals were tested simultaneously with LFT and PCR tests, and PCR was used as a gold standard to say someone is ‘positive or negative.’

Therefore, the sensitivity of LFTs was assessed for their ability to identify the same cases collected by PCRs.

“Still, it’s like comparing apples and oranges.”

The researchers reviewed data on how long people are infectious and used them to get the formula to recalibrate test efficacy data.

They estimated that of the group that tested positive for PCR, but that was asymptomatic and was lost to lateral flows, only half would have been infectious.

Therefore, previous studies estimating that lateral flows were less than 50% effective in detecting Covid probably underestimated its effectiveness significantly, the researchers said.

Professor Michael Mina, an epidemiologist at Harvard University, said: “There is a spectrum of infectious amounts of the Covid virus and we show that LFTs are likely to detect cases 90 to 95% of the time people are most infectious. “.

“Tests could achieve even 100% sensitivity when viral loads are at their peak and therefore capture almost everyone who currently poses a serious risk to public health.

“Most likely, if someone’s LFT is negative, but their PCR is positive, it’s because they’re not in the maximum transmissible phase.”

Professor Petersen added: “As LFTs are being widely used in schools, workplaces and for admission to places such as those used for large events, it is important that professionals of health and the public have clear information about the operating characteristics of the tests.

“We have shown that the absolute sensitivity to detect SARS-CoV-2 antigens is likely to be elevated with LFTs.

“To improve our understanding of its characteristics, longitudinal studies where individuals, and ideally case contacts, are tested daily using LFT and PCR tests would help to further understand false negatives (and false positives). ) and, above all, the time differences between turning positive PCR, positive LFT and onset of symptoms. ‘


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