When will your RTK-Ag and RT-PCR rapid tests show a positive result if you are infected with the COVID-19 virus?
The RTK-Ag test can usually detect infection on day 3 to 7 after a person is exposed to COVID-19 patients, while the RT-PCR test can detect infection as early as day 2 to 14 after infection. Therefore, the accuracy of RTK-Ag and RT-PCR tests is dependent on the duration of infection at the time the sample was taken. The use of the RTK-Ag test is recommended for individuals who are symptomatic or are in a high-risk group if asymptomatic. MOH has approved the use of RTK-Ag as an alternative method of testing COVID-19 other than RT-PCR. However, RT-PCR testing is still the gold standard for detecting COVID-19 infection.
RTK-Ag (Rapid Test Kit-Antigen)
- Not as accurate compared to RT-PCR test. It is for screening and not the diagnosis of Covid-19.
- Test can be performed by yourself at the comfort of your own home or by a trained practitioner.
- Results can be obtained very fast, after about 15 minutes.
- Test kits are not expensive, they can cost as low as below RM5.
Cassette type – More steps compared to Lolly test type. Straight forward, reliable if there is enough viral load.
Lolly test type – Easy, single test device. Takes longer time to collect enough saliva sample. If you take too long to collect your sample, the test may become invalid.
The polymerase chain reaction (PCR)
Amplifies small amounts of RNA from specimens into deoxyribonucleic acid (DNA), which is replicated until SARS-CoV-2, the virus that causes Covid-19, is detectable if present.
- More accurate compared to RTK-Ag and is a diagnostic test.
- Cannot be done at home yourself. The test is to be performed and analyzed by professionally trained personnel.
- It usually takes about 24 hours to get the result
- More expensive, from about RM200
RT-PCR technology to amplify small amounts of RNA. Photo: iaea.org
Bilakah ujian pantas RTK-Ag dan RT-PCR anda akan menunjukkan keputusan positif sekiranya anda dijangkiti virus COVID-19?
Ujian RTK-Ag biasanya boleh mengesan jangkitan pada hari ke-3 hingga hari ke-7 selepas seseorang terdedah kepada pesakit COVID-19, manakala ujian RT-PCR boleh mengesan jangkitan seawal hari ke-2 hingga hari ke-14 selepas dijangkiti.
Justeru itu, ketepatan ujian RTK-Ag dan RT-PCR adalah bergantung kepada tempoh jangkitan sewaktu sampel diambil.
Penggunaan ujian RTK-Ag adalah disarankan kepada individu bergejala atau berada dalam kumpulan berisiko tinggi sekiranya tidak bergejala. KKM telah meluluskan penggunaan RTK-Ag sebagai suatu kaedah alternatif pengujian COVID-19 selain RT-PCR. Namun, ujian RT-PCR masih merupakan gold standard bagi mengesan jangkitan COVID-19.
