What Is The Difference Between RT-PCR & RTK-Antigen Test?

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Where to get COVID test near me? Before seeking a test for COVID-19, it is important to know which exact type you need. There are three types of COVID-19 tests which are RT-PCR, RTK-antigen and antibody tests. The most common COVID-19 tests held in Malaysia are RT-PCR and RTK-antigen. But, what is the difference between these two tests? This article will help you to get to know the difference. 

RT-PCR Test

The COVID-19 RT-PCR test stands for COVID-19 reverse transcription polymerase chain reaction and is a method of examining the virus by detecting viral DNA or nucleic acid from SARS-CoV-2. This method has typically high sensitivity rates, though this also means the sample has to be carefully prepared to avoid contamination where highly professional staff is needed for sample handling. RT-PCR is a molecular test that is able to detect COVID-19 virus’ ribonucleic acid (RNA) in the individual’s nasal or throat swab sample taken. Chemicals are used on the swab in order to remove other substances and extract only the RNA from the sample. After that, the RNA is converted to DNA via the “reverse transcription” process, as well as extra short fragments of DNA are added to build DNA strands marker labels to detect the COVID-19 virus. The mixture is then placed in a machine that creates copies of the viral DNA, during which the marker labels release a fluorescent dye that can be measured by a computer. 

Besides, COVID-19 RT-PCR test is more accurate compared to the  Antigen Rapid Test Kit (RTK-Ag). The Ministry of Health (MOH) recognised this type of test as the gold standard for COVID-19 diagnostic tests which the results are to identify the SARS-CoV-2 (COVID-19) RNA. The SARS-CoV-2 RNA is detectable in respiratory samples during the acute phase of infection. This means that the RT-PCR test can detect a COVID-19 infection even before an individual becomes infectious and will allow early isolation. However, it also can only determine an active infection, not the past. On top of that, this test’s accuracy comes with a higher equipment price and more complex process. In comparison, the results of the PCR test also require a much longer time. Depending on the lab and logistics, results of the RT-PCR test can be obtained in two hours, or up to several days if the sample needs to be shipped across distances or other places. 

RTK-Antigen Test

The Antigen Rapid Test Kit (RTK-Ag) is also a common method used in Malaysia to determine if someone has contracted COVID-19, or active infection of COVID-19. Since 6th May 2020, Malaysia has been using RTK-Ag . RTK-Antigen test detects viral protein related to COVID-19 to determine a reactive or non-reactive result.  As the name suggests, rapid test is a faster method of detecting the virus in the body as it can generate results within 15 to 30 minutes. The rapid test only requires a swab sample from the nose to acquire results of reactive or non-reactive. The RTK-antigen test is cheaper and does not require sophisticated lab equipment. Somehow, it is less accurate than the RT-PCR test as it  sometimes tells people they do not have the virus when they actually do. 

On the other hand, the limit of detection for RTK-Ag is currently at Cycle Threshold (Ct) value of 30. RTK-Ag unable to detect any Ct value above 30. Ct value of 30 is equivalent to estimation of 300-400 viral copy numbers on the nasopharyngeal sample. In comparison to RT-PCR, it involves amplification steps and it’s limit of detection is about 4-5 viral copy numbers.

In addition, both RTK-Ag and RT-PCR are different platforms. RTK-antigen test’s results can be obtained within a shorter time and the services are beneficial when there is no molecular testing available at a specific place. RTK-antigen test is also an alternative to RT-PCR  where in some conditions for a comprehensive patient and public health management, testing using RTK-Ag shall be complimented with RT-PCR. 

Along with the tests now the Covid vaccines are also available. One must take the vaccine shot to prevent oneself from Covid-19. The WHO guidelines says if one has been infected before. He/she should wait for 3 months to get the vaccine. By then staying at home and wearing mask are the only options to be safe.

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