Coronavirus: Testing and why it matters
The UK government wants to do 100,000 coronavirus tests a day by the end of April, but has faced criticism for not increasing the number more quickly.
So, what tests are available and who are they for?
What coronavirus tests are there?
The tests currently being used in UK hospitals are to see if somebody currently has Covid-19.
These are done by taking a swab of the nose or throat, which is sent off to a lab to look for signs of the virus's genetic material.
The other type of test the government wants to use is an antibody test. These are done to see if someone has already had the virus.
They work by looking for signs of immunity, by using a drop of blood on a device, a bit like a pregnancy test.
The government bought three-and-a-half million antibody tests, but has not yet found one that is reliable enough to use.
How accurate are the tests?
The diagnostic tests used in hospitals are very reliable.
However, that doesn't mean they will pick up every case of coronavirus. A patient at the very start of their infection or with relatively low levels of the virus may show up as a negative.
And a swab may come back negative if it has not picked up enough of the virus from the back of the throat.
So far, antibody tests have not proved to be as reliable.
Health Secretary Matt Hancock said last week that 15 of the most promising antibody tests had been tested, but none was good enough.
Prof John Newton, who is overseeing testing, told The Times that tests bought from China had been able to identify antibodies in patients who had been seriously ill with coronavirus, but didn't pick up the milder cases.
Why is testing important?
There are two main reasons for testing people - to diagnose them individually, and to work out how far the virus has spread.
Having this second piece of information could help the health service plan for extra demand, including on intensive care units.
Testing could also inform decisions around social distancing measures. For example, if large numbers of people were found to have already been infected, then a lockdown might become less necessary.
And not testing more widely means many people might be self-isolating for no reason, including NHS workers.
Can I get tested?
Testing is not yet available for most people.
At the moment, most tests are reserved for seriously ill patients in hospital.
It means the majority of people who have symptoms can't find out if they are currently infected with coronavirus.
Tests are now being made available to doctors and nurses who have symptoms, or who live in a household with someone who does. Tests for other health and care workers will follow.
About 7,500 NHS workers and their family members have been tested, according to the Department of Health and Social Care.
Overall, 218,577 people in the UK had been tested by 7 April.
Why isn't the UK doing more tests?
The UK has not had the resources to do mass testing.
Health Secretary Matt Hancock said: "We have the best scientific labs in the world but we did not have the scale. My German counterpart for instance could call upon 100 testing labs ready and waiting when the crisis struck."
The government is aiming to carry out 100,000 tests a day in England by the end of April.
Scientists working in labs have reported challenges in getting hold of swabs, testing kits and reagents.
A reagent is the substance used to extract the virus's genetic material so it can be studied more easily. At the moment there is high global demand for reagents, which is why they are hard to obtain.
At first, Public Health England was only using its own eight laboratories. This has been expanded to 40 NHS labs - so, 48 labs in total.
The government says it is now working to recruit more laboratories at universities and research institutes. These will be used to test NHS workers.
Plans have also been announced to work with commercial partners such as Boots and Amazon, as well as with big pharmaceutical companies to build up the UK's diagnostic capacity.
How about the rest of the world?
South Korea, which has been able to test far more widely than the UK has, acted very quickly to approve the production of testing kits, allowing it to build up a stockpile.
Despite having a slightly smaller population than the UK, it has twice as many labs and about two-and-a-half times the weekly testing capacity.
Germany has carried out more than three times as many tests as the UK.
By 27 March, it had tested 1,096 per 100,000 citizens, while as of 1 April, the UK had tested 348 per 100,000 of the population.
That compares with 895 per 100,000 for Italy, 842 per 100,000 for South Korea, 348 per 100,000 for USA and 27 per 100,000 for Japan.
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