Also Known As
Coronavirus 2019 Test
SARS CoV-2 Test
COVID-19 PCR
COVID-19 IgG, IgM antibody test
Formal Name
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) RNA Detection by PCR
This article was last reviewed on
This article waslast modified on 27 May 2020.
At a Glance
Why Get Tested

Coronavirus disease is a global pandemic and public health emergency due to rapid human-to-human transmission. It was first described in China in late December 2019 and the first UK case was seen a month later. It is from a family of viruses called coronaviruses, and the disease it causes is called COVID-19. The exact name for the virus is severe acute respiratory syndrome ‘SARS-Cov-2’.

There are two main types of test for COVID-19:

  • A swab test – this is the ‘have I got it?’ test (to test current infection).
  • An antibody test – this is the ‘have I had it?’ test (to test for past infection.)

Testing is very important. It gives information about how many people in the country have, or have had, coronavirus. This means that it is possible to work out what restrictions in lockdown are useful, and what is not safe. It means that coronavirus in care homes or hospitals can be monitored.

When To Get Tested

Swab tests (for current infection) are most reliable if done 3-5 days after symptoms start, or around 8 days after being exposed to someone with the infection. The government has now said that anyone with symptoms can be tested.

Antibody tests (for past infection) are most likely to be helpful a few weeks after the symptoms have started. Research is trying to identify the best time for testing.

Sample Required?

Swab tests for current infection are tested with a swab to the mouth and/or nose. This is usually done by a healthcare professional, but home test kits are also available. This video gives further information on how to take a self-test swab.

Antibody tests need a blood sample.

Test Preparation Needed?

None

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

The nose and throat swab are tested for the presence of viral RNA (the genetic code) which signals current infection.

The blood is tested for antibodies which have been made because the body has been exposed to COVID-19 in the past.

Accordion Title
Common Questions
  • How is the test used?

    The tests are currently used to diagnose current infection (swab test) and work out past infection (antibody test).

    The swab test is most useful for people who are in hospital or care homes and need to have their infection confirmed.

    The antibody test is most useful for researchers who are trying to track how many people have been exposed to COVID-19, for example, in order to ensure that lockdown measures are released at the right time and plan for future healthcare.

  • When it is requested?

    The swab test has to be performed when there are high enough levels of the virus in the nose and throat. If the person is tested too early, then there may not be enough virus present to be picked up on the test. If the person is tested too late, there may be too little virus present in the nose and throat to be found on the swab. It is done using a technique called RT-PCR which looks for genetic traces of the virus.

    Antibody tests are more complicated. There are two main types of antibodies which the body makes in response to infection. IgM antibodies develop first (taking at least a week), and IgG antibodies later (about 2-4 weeks).

    There are several different ways to look for these antibodies. The most reliable is ELISA testing. A fingerprick test is being developed which may be able to give a quick result (a bit like a pregnancy test).

  • What does the test result mean?

    Swab tests for current infection

    • A test showing infection (positive result) is very reliable, and means it is very likely that you have COVID-19 infection currently.
    • A test not showing infection (negative result) means you are much less likely to have COVID-19 at the time. However it is important to know that sometimes people with coronavirus can be missed by swab tests. The test could be done too early or too late to give a positive result. The technique of taking the swab might not be good enough to get sufficient virus on it to show up on the test.

    When people who have COVID-19 are missed by the test it is called a ‘false negative’. It is not known exactly how many of these false negative results are expected.

    When researchers are studying large groups, to see how much virus is in the population, the false negatives do not matter so much. The results can be adjusted to take account of the numbers of false negatives expected.

    But they are much more important for individual people, especially health and social care workers. Most areas of the country are offering tests for these workers if they, or a member of their family has symptoms which could suggest COVID-19. But they may not be reliable enough to rule out COVID-19 infection. This means a health or social care worker could be falsely reassured by a negative test and return to work where they could pass on infection.

    This is why it is very important to thoughtfully consider whether we should trust a negative test result more than how much the ill persons symptoms suggest COVID-19.

    If you have strongly suggestive symptoms of COVID-19, it is safest to follow stay at home guidelines even if your swab test is negative.

    Antibody tests (blood tests for past infection)

    • A positive antibody test means that you are likely to have been infected with COVID-19 at some time. It does not necessarily mean that you are immune.
    • A negative antibody test means that means that your immune system has not produced antibodies, which means it is likely that you have not been infected with COVID-19 previously.

    These tests can be done too early or too late. This means that you could think you haven’t had covid, when you have, or that you have had covid, when you haven’t.

    These are new tests and we expect better information about how reliable they are in the coming months.

    These are useful because it allows researchers to track how much COVID-19 is circulating. Some people have very mild or no symptoms which means that the amount of COVID-19 in the country may be higher than the amount of people who have had symptoms from it.

     

  • Is there anything else I should know?

    Many private companies are now offering testing. Before purchasing a private company test it would be useful to determine what is the benefit of knowing the result; if there is no benefit then perhaps the test is not required.

    It is crucially important to know how reliable they are.

    ‘Accuracy’ is often given as a percentage, like ’this test is 98% accurate’.

    But this doesn’t mean that 98 out of 100 tests will be correct.

    This is because a test that shows an infection with COVID-19 (positive result) is more reliable when it is done in people at a high risk of disease, and it is less reliable when it is done in people with a lower risk of disease. You can read more information about this here.

    It is also important to know that a test showing that you have had COVID-19 does not mean that you are immune to it.

    It is a new disease and we do not have this information. Many coronavirus infections lead to some immunity, but there is not yet enough information to know whether this is useful immunity that will protect people from getting COVID-19 again.

    This is why people who have had COVID-19 infection are told still to observe all the restrictions to protect against COVID-19, such as travel restrictions and social distancing.

  • What are the symptoms of covid-19 infection?

    For information about the symptoms of COVID-19 see NHS website.