Covid-19 (CoronaVirus) by PCR Qualitative

Specimen Required

(eNAT Tube) Nasal Swab/Throat Swab

Fasting Required

Purpose of the Test

Why Get Tested Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2), which causes Coronavirus Infection Disease 2019 (COVID-19) has caused a 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. There are other coronaviruses known to cause human disease: NL63, 229E, HKU1, OC43, Severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS).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, COVID-19 infection. This means that it is possible to work out who needs to be treated for COVID-19, as well as to separate those with COVID-19 infection from other patients (to prevent onward infection). It can also be used to monitor the trend and spread of cases in a population, to determine what public health and societal interventions might be needed, and to assess the effectiveness of interventions, such as vaccines.

When this test is required

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). Furthermore, some tests detect antibodies to the viral spike protein (anti-spike antibodies), while others detect anti-nucleocapsid antibodies.There are several different ways to look for these antibodies with varying reliability. Fingerprick tests are commercially available and may be able to give a quick result (a bit like a pregnancy test), but these are of varying quality and are not recommended yet.

What the Test Detects

The nose and throat swab are tested for the presence of viral RNA (the genetic code) which signals current infection.Nose and throat swabs can also be used to directly detect the virus (antigen detection) by using a lateral flow test (LFT), lateral flow device (LFD), or rapid diagnostic test (RDT).The blood is tested for antibodies which have been made because the body has been exposed to COVID-19 in the past.See MoreSee Less

Preparation for the Test

None

Sample Requirements

Swab tests for current infection are tested with a swab to the throat 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.Other samples, such as sputum, may be tested if a patient is in hospital. Saliva testing may be used in some settings.Antibody tests need a blood sample.

Additional Notes

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.

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