What Tests are available?
The tests commonly available for SARS-CoV-2 can locate either:
- the RNA − detected by the PCR test
- the surrounding proteins − detected by the rapid lateral flow devices
- the human body’s response to the virus – detected by antibody tests.
PCR tests detect the virus’ RNA. These are usually done in a laboratory using a nose or throat swab. PCR tests are very sensitive and can locate even miniscule amounts of RNA. They are currently the best test for infections.
Patients with COVID-19 usually start to become positive by PCR testing 1-2 days before symptoms start and will continue to test positive by PCR afterwards for some time. This means a subsequent PCR test after a confirmed outcome is redundant.
The isolation period may vary according to when the test was taken or when symptoms began.
If you currently have symptoms that may indicate COVID-19, this is the test you should have to diagnose the infection.
PCR is the most accurate test available for current infection. False positives and False negatives are rare but doctors may take another test to remain on the safer side.
Lateral Flow Tests
These are the rapid tests that are used in the community. These can provide conclusions in 30 minutes and can be self administered. They detect proteins from the virus, not RNA. They use a swab of the nose and/or throat and are done through a plastic pregnancy test- looking device.
These tests differ greatly from PCR and are hence not ideal for patients with the Covid19 virus’ symptoms. Lateral Flow tests thus are largely for asymptomatic people.
These tests are not as sharp as PCR and are simply a way to test asymptomatic patients in a faster and more efficient manner.
The way to view these tests is that every extra positive case detected is a bonus, helping to contain the virus in undiagnosed communities.
If a person tests positive with a Lateral Flow test, they should verify this through an additional PCR. Meanwhile, they should reduce or omit contact with others.
These tests see the body’s response to a previous infection, by looking for antibodies that the body has produced.
There is a time lag after infection for the body to produce antibodies. So, antibody tests are not suitable for diagnosing people when they have symptoms.
They are useful for researching prior infections. This is useful in studies of how many people in a population have a history with the disease.
Levels of antibody are likely to reduce with time, over months or years, and thus is not an accurate conclusion on one’s past with the disease if there is a large time gap.
In the future, if a doctor needs to know if you have a history with the disease, they might perform an antibody test.
LAMP and LampORE Testing
Similar to PCR, LAMP and LampORE tests detect the viral RNA. They have an edge as they can also use saliva as a sample, alongside swabs. Recently LamPORE has been rolled out for local community testing in some places. This test can be undergone in mobile laboratories countrywide.