Your Complete Guide to PCR. PCR Test & RT PCR, CT Value Results.

Terms of CT PCR, CT Value, PCR Test & qPCR unfamiliar? this is the simplified straight to point guide. PCR (Polymerase Chain Reaction) is a technique used in molecular biology to amplify a single copy or fragment of DNA. The process is used to make many copies of a specific DNA sequence. PCR is also used to determine the presence of a particular DNA sequence in a sample. To understand the science behind this method, John Hopkins has a great summary. In this blog post, we will discuss what PCR is, how it works, and the different types of PCR tests that are available. We will also provide examples of RT PCR results and explain what they mean.

rt pcr test

What is PCR?

The science of PCR is complex, but the basic principle is simple. PCR amplification is a process that uses a DNA primer to initiate replication of a target DNA sequence. The primer binds to the target DNA molecule and provides a template for the polymerase enzyme to replicate the DNA sequence. This process can be repeated multiple times, resulting in the amplification of the target DNA sequence.

There are many different types of PCR, but the most common is RT-PCR (reverse transcription PCR). RT-PCR is used to detect the presence of a specific DNA sequence in a sample. The process begins with the reverse transcription of RNA into cDNA (complementary DNA). The cDNA is then amplified using PCR. The amplification of the cDNA allows for the detection of the presence of a specific DNA sequence.

PCR is a powerful tool that can be used to diagnose disease, identify genetic mutations, and more. PCR tests are available for a variety of different conditions and diseases.
Some of the most common RT-PCR tests include:


– HIV detection

– Breast cancer detection

– Cystic fibrosis diagnosis

– Cervical cancer screening

PCR Test is not the same as RTK Antigen read about the most common questions people ask.

How are PCR Test Samples Taken?

The sample for PCR testing can be taken from a variety of sources, including blood, tissue, or other bodily fluids.

How sensitive is PCR Test for COVID19?

The most common method of PCR Test for COVID is using RT-PCR testing method itself is extremely sensitive with 99.9% sensitivity, there has been contradicting research in Finland which could be due to the sampling method used usually nasal and throat swabs if done by an unskilled professional will result in false negatives.

What is PCR Test? for COVID19 Detection

PCR Test is used to detect Covid19. It amplifies the targeted types of COVID19 DNA or RNA so that it can be detected and measured.

COVID-19 testing uses a modified version of PCR called quantitative polymerase chain reaction (qPCR) or RT-PCR.

rt pcr ct value

qPCR Test

This method adds fluorescent dyes to the PCR process to measure the amount of genetic material in a sample. In this instance, healthcare workers measure the amount of genetic material from SARS-CoV-2. This is a quantitative method, meaning it calculates the amount of gene material expressed.


Another version of testing is RT PCR the most commonly used method globally. Essentially any SARS-CoV-2 (COVID19) DNA fragments present will be amplified. Scientists make use of the PCR innovation to magnify percentages of RNA from specimens into deoxyribonucleic acid (DNA), which is replicated until SARS-CoV-2 is observable if existing. The PCR test has been the gold standard test for identifying COVID-19. It’s precise and also dependable.

How to Read PCR Test Report?

PCR test results can be difficult to interpret, especially for those who are unfamiliar with the process. However, by understanding the basics of PCR testing, you can often decode the results yourself.

In the context of COVID19 we are looking at a result called the CT Value PCR test Result. There more more indept technicalities such as a genes threshold for CT value, that is beyond the scope of this post. Read more about it from Yale School of Medicne

Great illustration from Yale School of Medicine, CT Value illustration on cycle number (amplification times) Lower the CT Value higher the viral load higher the CT value lower the viral load.

What is CT Value?

In summary, this result describes how many cycles it takes of PCR methods to show a positive result in this case SARS-COV-2 (COVID19)

That means the higher the CT value the lower the more times PCR needs to amplify the SARS-COV-2 genes. Lower CT values mean a higher viral load therefore meaning you not only have COVID but maybe at an infectious stage, and should be cautious to stop the spread.

Higher CT Value (>20)Positive COVID19 Less Infectious
Lower CT Value (<20)Positive COVID19 More Infectious

COVID CT Value, Positive PCR Test Result

In Malaysia result <20 and below is considered infectious while values above 20 are considered uninfectious.

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