Why do some people get two coronavirus tests?

The Government was today accused of ‘fiddling’ its data to make it look like it had hit its target of testing 100,000 people in a day.

Health Secretary Matt Hancock today announced that 122,347 tests were carried out yesterday, April 30.

The tests done yesterday, however, were done on 73,191 people because many have to be tested more than once – and almost 40,000 of them were posted out to people and counted on the day.

In total, 762,279 people have been tested for the coronavirus in the UK in a total of 1,023,824 tests, meaning 13 tests are used on every 10 people tested.

This suggests one in every three people is tested twice.

People may be tested twice if something goes wrong during analysis, to confirm the result, or if a doctor receives a negative result for their patient and doesn’t believe it. 

While in other cases someone may be tested again after developing symptoms for a second time but testing negative in an earlier swab, meaning their most recent test is counted but they aren’t added again in the head count.

Others may have two swabs taken to be tested at once, one from the nose and one from the mouth, for example, meaning two tests are attributed to one person from the same occasion.

Swab testing is now being offered to anyone working or staying in a hospital or care home,  all essential workers, anyone who has to leave home for work, and anyone with symptoms who lives with someone over the age of 65 (Pictured: An NHS worker at a drive-through testing centre in Chessington, London)

The Government today claimed that it yesterday carried out more than 120,000 coronavirus tests, but faced criticism for counting ones that had simply been posted out to people

The Government today claimed that it yesterday carried out more than 120,000 coronavirus tests, but faced criticism for counting ones that had simply been posted out to people

Dr Paul Hunter, a former NHS doctor and now medicine lecturer at the University of East Anglia, told MailOnline it was ‘valid’ to retest people.

‘Because the test isn’t 100 per cent sensitive, it can fail for a number of reasons,’ he said.

‘Some of these reasons are in the labs themselves, where there are all sorts of controls that may go wrong. Sometimes the sample comes in damaged and you have to ask if the patient can send another.

‘The other issue is taking a swab. The person who does this might not do it right – for example, they might not manage to scrape against the back of the throat. ‘

One of the main reasons for multiple tests is likely to be because doctors don’t want to misdiagnose someone as having – or not having – the virus.

If someone is hospitalised with coronavirus symptoms and lives with someone else who has tested positive, for example, they would be retested if their first swab comes back negative. 

Dr Hunter said: ‘It may be that someone has symptoms synonymous with coronavirus – they have a sore throat and fever which has come on suddenly.

‘If this patient’s test comes back negative, the clinician might think something went wrong or “I better test them again just in case”.

‘I personally wouldn’t criticise the Government for including repeat swabs in their daily count. 

‘But it should only include swabs that have been examined in the laboratory – not swabs that are posted to people.’ 

The Government today faced backlash over a decision to include at-home tests in its count on the day they were posted and not the day they were processed in the lab, in a bid to push up its daily testing figure.

The Labour Party’s shadow health secretary, Jonathan Ashworth said: ‘Labour has repeatedly called for more testing, and increasing testing is an important milestone.

‘But many would have expected the 100,000 promise to have been met by actually carrying out testing, not simply because 39,000 kits had been mailed out.’        

Professor Keith Neal, an epidemiologist at the University of Nottingham, told MailOnline: ‘We know that tests don’t always work’. 

He added that sometimes people might be tested twice in one go.   

‘If you do a mouth swab and a nose swab they are separate samples, they would go through the assay separately and would be counted as two tests,’ he told MailOnline.

‘If you used the same swab for both it would be one test, but it’s not often normal to use the same swab.

‘For in-hospital cases it might be highly appropriate to make sure you don’t miss a diagnosis, particularly if you want to rule out COVID-19. If you do two tests the risk of a false negative is lower.’ 

Paediatric nurse practitioner Jessica Peck shared a diagram of how the coronavirus test is carried out on Twitter and said: 'This is how far back we have to put the swab to test you for #COVID19z. You might want to follow medical recommendations and #StayAtHome'

Paediatric nurse practitioner Jessica Peck shared a diagram of how the coronavirus test is carried out on Twitter and said: ‘This is how far back we have to put the swab to test you for #COVID19z. You might want to follow medical recommendations and #StayAtHome’

WHAT IS THE SWAB TEST FOR CORONAVIRUS? 

Nasopharyngeal swabs are used to detect respiratory viruses, such as the flu and the new coronavirus.

It is the preferred choice for SARS-CoV-2 testing, according to the Centers for Disease Control and Prevention (CDC).

It involves inserting a long, flexible cotton bud into the nostril and along the nose ‘floor’. This is supposed to be done slowly so that it is comfortable.

The aim is to reach the posterior nasopharynx, a cavity made up of muscle and connective tissue, covered in cells and mucous that are similar to the nose. It continues down into the throat.

The swab is rotated several times in order to get enough cells.

The sample is then sent to a lab, where it will be tested to determine if the patient’s cells are infected with the virus.

The coronavirus is a RNA virus, which means it uses ribonucleic acid as its genetic material. A process called reverse transcription is needed to transcribe the RNA into readable DNA.

A swab sample doesn’t collect much RNA in one go, therefore a polymerase chain reaction (PCR) is used to rapidly make billions of copies so it can be analysed.

The DNA is dyed a fluorescent colour, which glows if the coronavirus is present, confirming a diagnosis.

Swab testing is usually carried out by a medical worker pushing a long cotton bud through someone’s nostril into the top of their throat.

It can be an uncomfortable procedure and it can be tricky to get the right types of cells on the end of the swab.

The coronavirus is most present in the epithelial cells in the airways, which can be found in the airways at the back of the nasal cavity, therefore the swab must be inserted deep into the nose and moved around. 

The sample is then sent to a lab, where it will be tested to determine if the patient’s cells are infected with the virus. 

Access to swab tests has now been extended to allow some people to take their own samples at home and return them to the Department of Health by post.

Some of these may need to be redone because people aren’t qualified to do the tests properly and may not carry out a thorough enough swab. 

The introduction of self-testing at home today caused furore today as Matt Hancock’s department was accused of fiddling with statistics to make it look like the Government had hit its 100,000-in-a-day target. 

The Health Secretary bullishly claimed success at the Downing Street briefing this evening, saying there were 122,347 tests done in the 24 hours to 9am.  

But it emerged that the Department of Health is counting tests kits that have been sent out to homes and hospitals – even though they have yet to be returned and processed.

The head of the testing programme, Professor John Newton, confirmed tonight that around 40,000 of the total were kits that have been mailed out – suggesting 100,000 tests have not in fact been completed.

Mr Hancock dodged questions about whether the figures had been cooked this evening, saying the allegation was ‘not something I recognise’.

But Boris Johnson told the Downing Street briefing last night that the figures covered tests ‘carried out’, rather than merely posted. Labour accused ministers of ‘moving the goalposts to hit their own arbitrary target’.

A tweet sent from the No 10 account earlier this month stated: ‘We’ll test 100,000 people a day by the end of this month.’

But the details showed that in fact just 73,191 people were tested, some more than once. 

When Mr Hancock set the target he said he wanted 100,000 tests per day – but the number of people checked has always been significantly lower, as many need to be screened multiple times, often to avoid false negatives.

A jubilant Mr Hancock said tonight: ‘I can announce that we have met our goal… Setting stretching, ambitious goals in a crisis has a galvanising effect on everybody involved. It is a mission.’

HOW THE GOVERNMENT IS RAMPING UP TESTING 

As it steps up surveillance of COVID-19 the Government is now moving into four major population testing schemes:

100,000 RANDOM TESTS

Imperial College London will oversee the two-part REACT programme (Real-time Assessment of Community Transmission).

The first part of this will be the 100,000 tests of random people in 315 different areas of the UK, to see how many of them are currently infected.

RANDOM ANTIBODY HOME TESTS 

Part two will be a rollout of at-home antibody tests, which can tell whether people have already had the disease and recovered. These will be given to 300 people for an initial trial and then rolled out to 10,000 people and then to 100,000 if it is successful.

The antibody tests will create a picture of how many people have had the virus already and may have immunity to it, meaning they won’t catch it again, at least in the short-term.

REGULAR SWAB TESTS FOR 25,000 

These two testing phases will run alongside two other long-term programmes announced last week as part of the Government’s ‘test, track, trace’ plan.

At least 25,000 people will be enrolled into a scheme in which they will have regular swab tests taken at monthly intervals to see if they are infected at the time. This will continue for the next year and will be scaled up to include 300,000 people if it is found to be useful.

REGULAR ANTIBODY TESTING 

And further antibody testing will be rolled out to 1,000 households across the country in which people will give blood samples for analysis to test whether they have developed immunity to the virus.

Sir Patrick Vallance, Britain’s chief scientific adviser, yesterday confirmed officials are using population testing and data on official cases of coronavirus to work out how fast the virus is spreading, signified by its R, or R0, value.

He said: ‘At the moment we’re using a calculated R looking at all sorts of things including contacts, looking at genomics, looking at data from ambulances, hospital admissions, and so on, to calculate the R.’ 

Lord Ara Darzi, director of the Institute of Global Health Innovation at Imperial College London, explained on BBC Radio 4 this morning: ‘[This] will be a snapshot of the R value across the country. We’ll be testing 100,000 people in 315 local authorities, randomly selected, and the snapshot will give us not just the R value on a national level, but also a local community level, which is also critical.

‘We are up and running, we’ve sent nearly 2,000 and it will take about a couple of weeks to get them all out and back, and obviously we need to analyse these and inform policymakers, because this will have a significant impact in terms of easing the lockdown.

‘There’s another study going on at Oxford in 20,000 households which will be repeat tests… so the combination of these two studies will be very informative in terms of moving into the next phase.’ 

CONTACT TRACING 

As well as stepping up testing the Government will also employ an army of 18,000 contact tracers – likely to be repurposed civil servants – by mid-May.

These will be tasked with contacting people who have tested positive for the coronavirus and gathering details about the social networks around them, enabling them to isolate people who might have it and stop them spreading it further.