When someone performs a PCR test, usually the term CT value will be attached to the examination results. However, there are still many people who may not understand what a CT value is and how to read it.
In the examination of the COVID-19 test via PCR, generally people only know the positive or negative status. In fact, apart from that, the CT value in the PCR test also has an important role.
Research shows that high or low CT values play a role in predicting the severity of COVID-19 disease and the patient's risk of dying from COVID-19.
Know What is CT Value
PCR test (polymerase chain reaction) can detect the presence of genetic material (DNA and RNA) of certain bacteria, viruses, or cells, including the Corona virus. In the PCR test for COVID, the examining machine will perform amplification (repeated checks) to determine whether the sample contains the genetic material of the Corona virus.
One cycle of this amplification is called the CT value or ccycle threshold value. In short, the CT value can be referred to as the cycle threshold value. Usually the repetition of the amplification process to detect the presence of Corona virus DNA or RNA in PCR examinations is 40 or called a CT value of 40.
However, each laboratory can use a different threshold and range between 35-45 times or with a CT value of 35-45.
If the DNA or RNA of the Corona virus is detected in 40 repetitions of amplification, the result of the COVID-19 PCR test is positive. Usually, the examiner will include in what cycle the genetic material of the Corona virus was detected.
For example, if a positive Corona virus is detected during PCR amplification in the 25th cycle, then the result is a positive PCR with a CT value of 25.
How to Read CT Value Numbers
Generally, a person's PCR test result is negative if the CT value exceeds 40, depending on each laboratory. This means, in 40 repetitions of PCR amplification, there was no SARS-CoV-2 virus genetic material in the samples examined.
To find out more detail how to read the CT value lift in the RT-PCR examination, here is the explanation:
- CT value <29 is a strong positive reaction, meaning that the number of detected virus particles may be quite large
- The CT value of 30–37 is a positive reaction, meaning that the number of detected virus particles is moderate
- The CT value 38–40 is a weak positive reaction, meaning that the number of virus particles detected is small
- CT value >40 and above is negative, meaning that not a single virus particle has been detected in the body
The CT value in the PCR examination for COVID-19 is considered to be able to predict how much Corona virus is in the patient's body. However, until now there has been no research that can confirm that the CT value can be a benchmark for the amount of Corona virus in the body for sure.
In addition, the CT value cannot be used as the main benchmark for assessing the severity of COVID-19. In order to determine the condition and severity of COVID-19 in patients, other examinations are still needed by doctors, such as physical examinations, blood tests, blood gas analysis, and radiological examinations, such as chest X-rays.
However, the results of the CT value PCR for COVID-19 are still useful for helping doctors determine the treatment and care steps for COVID-19 patients, whether they require treatment in a hospital or only self-isolation.
Whatever the CT value results you see after doing the PCR examination, it is still important to consult a doctor, so that Anga can get the right treatment and recommendations according to your condition.
If you still have questions regarding the Corona virus and its examination, ask your doctor directly through the ALODOKTER application. In this application, you can chat directly with a doctor or perform teleconsultation services with Alodokter's personal doctor.