20 October 2020
The different methods of the Rapid Test Kit Antigen (RTK Antigen) and Reverse Transcription Polymerase chain reaction (RT-PCR) test is the reason why sometimes the results of the Covid-19 test may not reflect the actual situation, said State Health director Dr Chin Zin Hing.
He said this was the reason why travellers whose negative RTK Antigen test taken at Kuala Lumpur International Airport (KLIA) turned up positive upon taking the RT-PCR test at Kuching International Airport (KIA).
“For tests done at KLIA previously using mainly the RTK Antigen, the method is different from the RT-PCR test so sometimes the results may not reflect the actual situation.
“That’s why when some were tested using the RTK Antigen in KLIA, they tested negative but when they came back and we use the RT-PCR test, they are found to be positive of Covid-19.
“Because of the different methods, the sensitivity and the specificity of the tests could be different,” he told a press conference at the old State Legislative Assembly (DUN) Building here yesterday.
He was clarifying on queries made by certain quarters questioning why Covid-19 tests taken at KLIA were negative but had changed to positive upon taking another test here.
Dr Chin cited an example where Sarawak’s two imported cases from Sabah on Wednesday who had undergone the RT-PCR test there, five days before they arrived in Kuching.
“For us, we need them to be tested within three days and though their RT-PCR test in Sabah was found to be negative, we repeated the test for these two and they came back positive.
He said for these two cases, when they took the test in Sabah, it could be during the incubation period so it was most likely too early to pick up the Covid-19 virus.
“So when they came here, it’s already past five days so we tested them again and this time, we can detect the virus.
“It’s the same test but because of the different timing so despite testing negative initially, when they repeated the test again five days later, it came back positive,” he said.