CT scans could be better way to diagnose coronavirus than swab tests, experts argue – The Sun
The technology was widely used to diagnose cases in China where scientists say they were able to detect "tell-tale" signs of Covid-19.
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It comes amid reports that the current nasal and throat swab tests for coronavirus are missing up to 30 per cent of infected people – known as "false negatives".
To reduce the risk of a second wave and ensure an exit strategy can go ahead, some doctors are calling for CT scans to become a more routine method of testing.
CT scans are able to identify hazy, patchy, “ground glass” white spots in the lung – a telltale sign of the killer illness, according to Stat.
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A recent study, published in the journal Radiology, found that scientists in China were able to detect 97 per cent of Covid-19 infections from chest CTs.
In comparison, the research found that 48 per cent of patients who had negative results on the swab test actually had the disease.
Doctors from The Mount Sinai Health System in New York, who analysed the lung scans, said they were able to identify specific patterns in the lungs as markers of the virus as they developed over two weeks.
They said that it could help to quickly diagnose Covid-19 cases – perhaps before symptoms even appear.
Dr Adam Bernheim, who led the research, told DailyMail.com: "CT scans are an extremely powerful diagnostic tool because you can see the inner organs in a three-dimensional way.
"And you can see the manifestation of many diseases."
However, the American College of Radiology has urged doctors to only use CT machines in very specific circumstances when assessing coronavirus patients.
It also said that CT “should not be used” to screen for – or as a first-line test to diagnose – the virus.
Part of the concerns is that infected patients could contaminate the machines and put them out of action while they are deep-cleaned.
In a statement, the professional body said: “To date, most of the radiologic data comes from China. Some studies suggest that chest CT in particular may be positive in the setting of a negative test.
“We want to emphasise that knowledge of this new condition is rapidly evolving, and not all of the published and publicly available information is complete or up-to-date.”
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It added: “Depending on the air exchange rates, rooms may need to be unavailable for approximately one hour after imaging infected patients.
“These measures to eliminate contamination for subsequent patients may reduce access to imaging suites, leading potentially to substantial problems for patient care."
There are also concerns that CT scans could expose people to a low dose of radiation.
Dr Sarah Jarvis, GP and clinical director of Patientaccess.com, said: "There has been a lot of interest in whether CT scans are a more accurate way of diagnosing Covid-19 than current swabs.
"If you have a positive result from a swab test, it’s highly unlikely to be wrong.
"But quite a lot of people have negative tests if the swab isn’t taken correctly.
"However, there are down sides to CT scans as well.
"Apart from availability of machines for mass testing, CT scans do expose people to radiation, albeit at a low dose.
"And while they’re extremely accurate for people with more severe disease (they show a classic ‘ground glass’ appearance in the lungs), less is known about how accurate they are for people with mild or very early infection."
Another problem is that CT scans cannot easily distinguish between Covid-19, SARS, MERS, and other viral pneumonia, including from influenza.
Sanjat Kanjilal, an infectious disease physician at Brigham and Women’s Hospital in Boston, told Stat: “They’re not specific enough.
“That makes me sceptical that it can have a big role to play."
It comes after evidence from China suggests that up to 30 out of every 100 people with coronavirus might test negative.
Experts say the main reason is that the sample collected isn't good enough to show any signs of the virus.
The swab is supposed to be pushed into the back of the nose and then curve down into the throat.
It is an uncomfortable, and sometimes painful, method – and sometimes the swab doesn't reach far enough or remain in place long enough to get a good enough sample.
For now, the government advice remains that for those that show symptoms – a fever or a new and persistent cough – should self-isolate.
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