Factors that contribute to false rapid test results
The Thai government agreed to allow the use of rapid antigen test kits for Covid-19 because the rate of false positives is low at just 3 per cent. However, these false positives can be caused by many factors.
In a Facebook post on July 28, Thiravat Hemachudha, chief of Chulalongkorn University’s Centre for Emerging Disease Health Sciences, said a negative result from an antigen test for an asymptomatic person does not mean they are completely free of the virus. Similarly, a positive result for an asymptomatic person does not mean they have the virus, but it is necessary for them to undergo a proper RT-PCR test.
The Covid-19 Information Centre, meanwhile, has issued a list of factors that may result in false test results:
A false positive can be caused by four factors:
• Contamination of the equipment or testing area
• Presence of another virus or microorganism
• The test has been wrongly conducted
• Quality of specimen is bad
A false negative can be caused by three factors:
• The infection is just starting and there is a low amount of virus
• Specimen has been wrongly collected
• The test has been taken incorrectly like too much time spent on the reading or insufficient sample