Coronavirus Tests

There are two types of tests available to diagnose the coronavirus; viral and antibody. 

A viral test will reveal whether an individual has an infection at the present time. Meanwhile, an antibody test determines whether the patient has experienced an infection in the past.

Coronavirus tests: Viral and Antibody

Viral coronavirus tests involve taking a swab from inside the nose or the back of the throat. This option will detect whether or not the patient has COVID-19 at present. It will not reveal whether a patient has encountered the virus and recovered.

In contrast, coronavirus antibody tests require a blood sample. A simple drop from a pricked finger is sufficient. The antibody test shows whether the patient has been affected by COVID-19 in the past. If they have, antibodies will be found in the blood. 

It usually takes 1-3 weeks after infection for human bodies to produce antibodies. This means that an antibody test is not a reliable way of showing if an individual has a current infection. That’s why viral tests are used instead. 

Who should be tested for Coronavirus 

The WHO has advised that, where possible, testing is made a priority. If a person has mild symptoms of COVID-19, they do not necessarily need to be tested for the virus. Decisions over who must be tested for coronavirus vary from nation to nation. It will depend on the availability of tests in that specific country. Demand for testing is high and the availability of tests is lower in some areas.

In most instances, priority for coronavirus tests is given to those who are high-risk for developing a severe infection. For example, the elderly, obese or those with underlying health concerns. Priority may also be given to those who are primary caregivers for dependents. 

The CDC has advised guidelines on categories of people who should receive the highest priority for coronavirus tests. Such people are:

• Hospitalised patients displaying symptoms of coronavirus 
• Healthcare professionals and first responders with symptoms
• Residents of care facilities and shelters who are displaying symptoms

People who are considered a secondary priority for testing are those showing symptoms of infection.

How accurate are coronavirus tests?

Tests for coronavirus are reasonably accurate. But no test is 100% accurate. 

The timing of the test, how the swab was taken and the handling of the sample may affect the accuracy of the results. This is why considerations must be made for false negatives and false positives. 

The accuracy of all medical tests is determined by sensitivity and specificity. The sensitivity of a test (also known as the true positive rate) is defined as the percentage of infected subjects who yield a positive result. Clinical tests are seldom 100% sensitive – this would identify all patients who are infected. A test with 90% sensitivity will identify 90% of patients who have the disease but will miss 10% of patients who have the disease.

The specificity of a test is also known as the true negative rate. This indicated the number of people without the disease who will yield a negative test result. So, specificity dictates a tests’ ability to identify patients who do not carry the disease. A test that is 80% specific will identify 80% of patients who do not have the disease.