Covid-19 tests: Over-the-counter test, breathalyser, antigen rapid test - what's the difference?

SINGAPORE - A variety of Covid-19 tests - with the latest being over-the-counter test kits - are now under Singapore’s belt, allowing fast, extensive, easy and accurate tests to be conducted as the nation raises its game to fight the virus.

Here's a look at the different tests.

1. Reverse transcription polymerase chain reaction test (RT-PCR)

Swab test from the nose or back of throat, or from sputum. Looks for genetic sequences of Covid-19.

Cost: Over $150 to $200 for pre-departure testing. If you have been advised by your doctor to take a swab test, this will be free.

Time taken: A few hours.

Ease of use: Requires the use of specialised lab machines.

Accuracy: Gold standard for testing. Sensitivity rate (ability to detect those who are positive): more than 93 per cent.

Other details: Very uncomfortable. An average of over 55,000 PCR and ART tests were carried out each day in the second half of May.

2. Antigen rapid test (ART)

Some involve using a nasal swab from the lower part of the nose. Looks for proteins on the surface of the virus called antigens.

Cost: As low as $10.

Time taken: 20 to 30 minutes.

Ease of use: Deployment is very flexible because it is a handheld device and can be done en masse with many people being swabbed at the same time. ARTs have been rolled out to almost all the public health preparedness clinics that are providing the “swab and send home” service and all polyclinics. 

To expand testing capacity, the Government is hoping to deploy them to private GPs as well. 

Accuracy: Not as accurate as PCR tests, but able to pick up infections early. Sensitivity rate: 82 per cent.

Other details: Those with acute respiratory symptoms are required to take an ART test on top of a PCR test to allow for faster detection of cases. Used heavily for pre-event testing.

3. Breathalyser

No swabbing; just blowing into a mouthpiece or cartridge.

Cost: Estimated to be around $25.

Time taken: 1 minute.

Ease of use: Involves some equipment.

Accuracy: Silver Factory Technology reported that its breathalyser has a sensitivity rate of over 95 per cent and specificity of more than 99 per cent when compared with PCR kits.

Other details: Used at the Causeway and the airport.

ALSO READ: Covid-19 tests in Singapore: Its cost and where to go

4. Over-the-counter tests

Like pregnancy kits, these could be ART tests which are purchased from pharmacies and  administered at home.

Cost: Price to be confirmed.

Time taken: ART usually takes 20 to 30 minutes.

Ease of use: Ease of use to be confirmed.

Accuracy: ART tests typically have a sensitivity rate of 82 per cent.

Other details: People who are worried about Covid-19 and wish to put their mind at ease, such as front-line workers who may wish to test themselves daily. Will be simple to use and not so uncomfortable.

5. Wastewater testing

Detects the presence of the virus at a location. This can then be followed up with clinical tests. Frequency of sample collection varies from site to site and depends on the purpose of surveillance.

Other details: Locations islandwide that have had their wastewater surveyed include the four water reclamation plants, workers' dormitories, nursing homes and hostels.

6. Pooled testing

One PCR test on a group of suspected cases. If the pooled test yields a positive result, all the people in the group will be tested individually to fish out the Covid-19 case.

Other details: Usually conducted in dormitories to get a sense of the prevalence rate of Covid-19 there.

ALSO READ: Singapore provisionally approves 60-second Covid-19 breathalyser test

This article was first published in The Straits Times. Permission required for reproduction.