Coronavirus tests: Methods, availability, and accuracy

Most tests for the new strain of coronavirus involve taking a swab sample for analysis.

The virus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 19 (COVID-19).

Developing reliable tests for the virus is essential to slow its spread.

Currently, these tests are for people at risk of developing severe COVID-19. For example, healthcare professionals will likely prioritize testing for older adults who may have the infection.

This article will discuss how COVID-19 tests work and who is receiving them.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

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There are several ways to test for the new strain of coronavirus. Most are either molecular or serological tests.

Molecular tests

Molecular tests look for signs of an active infection.

They usually involve taking a sample from the back of the throat with a cotton swab. The doctor then sends the sample off for testing.

The sample will undergo a polymerase chain reaction (PCR) test. This type of test detects signs of the virus’s genetic material.

A PCR test can confirm a diagnosis of COVID-19 if it identifies two specific SARS-CoV-2 genes. If it identifies only one of these genes, it will produce an inconclusive result.

Molecular tests can only help diagnose current cases of COVID-19. They cannot tell whether someone has had the infection and since recovered.

Serological tests

These tests detect antibodies that the body produces to fight the virus. These antibodies are present in anyone who has recovered from COVID-19.

The antibodies exist in blood and tissues throughout the body. A serological test usually requires a blood sample.

Serological tests are particularly useful for detecting cases of infection with mild or no symptoms.

The Centers for Disease Control and Prevention (CDC) are currently developing a serological test for SARS-CoV-2, and they are looking for blood samples from anyone who has had COVID-19. The samples would be taken at least 21 days after symptoms first developed.

There are different options for testing.

Public tests

In the United States, 91 public health laboratories have completed verification to test for COVID-19.

Testing is available in all 50 states, plus the District of Colombia, Guam, and Puerto Rico. To get a test, the CDC recommend contacting the state health department.

For people with Medicare, most of whom are 65 or older, the prices of these tests vary from $35–52, depending on the state.

It is important to note that these tests are currently limited to people in danger of serious illness. Those at risk include:

• people with severe symptoms
• people with underlying health conditions
• pregnant women
• older adults

Home tests

Home tests for COVID-19 are currently in development.

The U.S. government is working with the Gates Foundation and others to develop home tests. These tests involve taking a sample at home and sending it off to a laboratory to check for signs of the virus.

There are different ways to collect swab samples. First, it is important to determine the most effective and safe method of home testing.

Some companies are already offering home testing kits. However, it is currently not possible to guarantee the safety or reliability of these kits.

COVID-19 tests are new, and assessing their accuracy is challenging.

PCR tests may produce false negatives, failing to identify evidence of SARS-CoV-2.

Sometimes false negatives result from human error or problems with the procedure. Giving the test too early or late, for example, can lead to a false negative.

The accuracy of similar tests for influenza is generally 50–70%.

As of March 23, 2020, there have been 4,649 tests by CDC laboratories and 75,263 tests by public health laboratories in the U.S.

These figures refer to the number of specimens tested, rather than the number of people. Some people give multiple samples for testing.

The true figure is higher, due to a delay in official reporting.

The U.S. has been slower than other countries to take up COVID-19 testing. Accounting for population size, the U.S. is administering far fewer tests than many European and some Asian countries.

For example, the U.S. has administered around 314 tests per 1 million people. The same figure for the United Kingdom is 960, while for Germany it is around 2,023 and for South Korea it is 6,148.

The U.S. is also administering almost ten times fewer tests than Canada.

The low rates of testing in the U.S. mean that more people are likely to have COVID-19 than national figures suggest.

Anyone with the following symptoms should contact a healthcare provider:

• a cough
• shortness of breath
• a fever

Tests are in short supply and are only available for people at risk of severe illness. A doctor will determine whether a person’s symptoms necessitate a test.

Anyone with a chronic health condition and anyone over the age of 60 should receive a test.

Most people who develop COVID-19 have a relatively mild form of the disease, which does not require specialist treatment in a hospital.

Mild symptoms may include a fever, a cough, a sore throat, tiredness, and shortness of breath, which may last 1–2 weeks.

Other people who have the infection may experience no symptoms.

For some people, COVID-19 is a severe illness. The risk is higher for people who are older or who have chronic health conditions, such as diabetes.