Antigen rapid tests accounted for roughly 60 per cent of all Covid-19 tests conducted nationwide in June, according to the National Institute of Public Health (NIPH).
In a guideline on how to use the rapid test kits issued on July 15, NIPH said around 75 per cent of Covid-19 cases confirmed last month were detected through the devices.
It said the kits have helped ease the burden on polymerase chain reaction (PCR) test machine and reduce the risks of community outbreak as they can produce results in 15-30 minutes.
The guideline said the kits can detect the virus in individuals who are asymptomatic and those who are carrying high levels of the virus. It explained that the risks of transmission are high one to three days before infected persons show symptoms and five to seven days after they do.
The World Health Organisation (WHO) recommends rapid antigen test kits for Covid-19 that meet the minimum performance requirements of at least 80 per cent sensitivity and 97 per cent specificity,
Sensitivity measures how often a test correctly generates a positive result for people with a particular condition, while specificity represents the proportion of people who do not have the condition and who test negative.
For instance, a sensitivity of 80 per cent means that results will not turn out positive for 20 per cent of people with a condition who undergo testing. This depends on a number of factors, such as the time from the onset of the infection, the viral load, and quality and effectiveness of the device.