COVID-19 Testing FAQs - Articles - Health Corner

What is COVID-19?

COVID-19 is the illness caused by the new coronavirus (SARS-CoV-2).

People infected with COVID-19 can have a wide range of symptoms, ranging from being completely well, to being severely ill.

Those of older age or those with underlying comorbid illness are at higher risk of serious illness and complications.

Symptoms can appear from one day to two weeks after exposure, and may include:

Fever and chills	Muscle/body aches
Cough	Headache
Shortness of breath	Loss of smell (anosmia) and/or taste
Sore throat	Congestion/runny nose
Nausea and/or vomiting	Diarrhoea

Should I have a coronavirus test?

If you experience any of the above symptoms, even if mild, or you have a known or suspected exposure to the virus, you should have a coronavirus test.

What kinds of coronavirus test are there?

There are two main types of tests for coronavirus: tests that look for the virus itself, and tests for antibodies to the virus.

How are they performed?

The antibody test is done on blood. A small amount of blood is drawn from a vein, though there are some tests which only require a drop of blood from a pinprick.

The viral tests look for viral RNA via a Polymerase Chain Reaction (PCR).

Currently, most viral tests look for virus in the back of the throat, with the sample usually being ‘deep throat saliva’ or a ‘nasopharyngeal swab.’

The antibody test looks for two different types of antibody:
IgM – which appears early and disappears early
IgG – which appears later and persists for longer

Which should I have?

It depends on the problem. If you want to know if you currently have coronavirus infection, a test that looks for the virus directly is best.

If you want to know if you have had the virus, an antibody test is best.

Currently, it is not clear whether a positive antibody test confers immunity against future infection with SARS-CoV-2, or how long potential immunity will last. It can also take a while for antibodies to be detected.

Antibody tests cannot be used to diagnose current infection

How do I get a test?

Your doctor, government health centre, a private or public hospital can arrange. Your doctor will take the nasopharyngeal swab or blood and send it to the laboratory.

For the deep throat saliva test, your doctor will provide you with the test kit. You provide the sample at home the following morning, and either deliver it to a collection point yourself, or you can arrange to have the sample collected.

Details are at https://www.coronavirus.gov.hk/eng/early-testing.html

Interpreting COVID-19 Test Results

Type of Test	Result	Interpretation
Viral Testing	Positive	Most likely DO have and active infection and can infect others
Viral Testing	Negative	Most likely DO NOT have an active infection
Antibody Testing	Positive	Likely have HAD an infection OR vaccinated
Antibody Testing	Negative	Likely NEVER HAD an infection, OR have not yet developed antibodies
Both (Viral + Ab Testing)	Viral Positive, Antibody Positive	Most likely DO have active infection and can infect others
	Viral Positive, Antibody Negative	Most likely DO have active infection and can infect others
	Viral Negative, Antibody Positive	Likely have HAD and recovered OR vaccinated
	Viral Negative Antibody Negative	Likely NEVER HAD COVID-19

False Positive: Test result should be negative because you do not have COVID-19 but the test result is positive

False Negative: Test result should be positive because you do have COVID-19 but the test result is negative

Source: Centre for Disease Control and Prevention, USA

What is COVID-19?

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