Coronavirus test. File photo: Bernama

KUCHING: State Health Department (JKNS) director Dr Chin Zin Hing has shed some light on results of Covid-19 tests in the state.

This pertains to why some individuals who tested negative for Covid-19 just before entering Sarawak but later tested positive upon undergoing a reverse transcription polymerase chain reaction (rT-PCR) test in Sarawak.

He said that two positive cases from Sabah reported by the Sarawak Disaster Management Committee (SDMC) on Wednesday had indeed undergone an rT-PCR test in Sabah with negative results, five days before arriving in Sarawak.

“We need them to be (tested) within three days, so we repeated the test for these two persons here and they tested positive,” he said at the SDMC Covid-19 update press conference today.

He explained that when these individuals had undergone the rT-PCT test in Sabah, this could have been during the incubation period when it is likely too early to pick up the virus.

“But when they come here, it was already past five days. So we tested again, and this time, we could detect the virus,” he said.

He added that the same test type (rT-PCR) was used, but due to the difference in timing, the initial test result was negative whereas the following result was positive.

As for testing in Kuala Lumpur International Airport (KLIA), Dr Chin said that the method of testing that is used there is through an antigen rapid test kit.

“This is a different method from the rT-PCR test. So sometimes the result may not reflect the actual situation,” he said.

He said this is the reason why some people tested negative for Covid-19 via the antigen rapid test kit in KLIA, but later they tested positive via rT-PCR in Sarawak.

“The sensitivity and specificity of the tests could be different,” he explained.