The term CT value in the PCR test (CT value PCR) is increasingly being discussed by many people. Some of them may already understand CT value PCR, but there are still many people who do not understand and ask questions about this term. So, what exactly is CT value PCR?
CT value or ccycle threshold value is a value that appears in the PCR test. CT value PCR serves to help determine the status of whether a person is positive or negative regarding Corona virus infection.
In addition, CT values can also help doctors predict the possible amount of Corona virus in the body and determine the patient's risk of experiencing complications or severe symptoms of COVID-19.
Understanding CT Value in PCR Test Results
RT-PCR test (Reverse-Transcriptase Polymerase Chain Reaction) is one of the examination methods to diagnose COVID-19 by detecting genetic material from the corona virus or SARS-CoV-2.
This test is generally recommended to be performed on patients whose antigen swab results are positive, or who have had close contact with a confirmed COVID-19 patient.
In the results of the PCR test, there is a CT value that can be an indicator to determine the possibility of how much virus there is in the patient.
This CT value refers to the number of amplification cycles or repeated examinations of the sample until the Corona virus component can be detected by the PCR examination machine.
In general, the amplification process in the PCR examination will occur repeatedly until it reaches 40–45 cycles, depending on the laboratory. In laboratories that set a CT value of 40, this means that they repeat amplification to detect Corona virus DNA or RNA up to 40 times in the PCR test carried out.
If in the 40 repetitions the examiner succeeded in detecting the Corona virus, then the PCR test was declared positive. After that, the examiner will also attach to the amplification cycle how much genetic material of the Corona virus was found.
For example, if the DNA or RNA of the Corona virus in the sample is detected in the 20th cycle, then the result is a positive PCR with a CT value of 20. Meanwhile, if in 40 repetitions of the PCR no Corona virus is found, then the PCR test result can be declared negative.
Why it's Important to Understand CT Value PCR
The results of the PCR examination are actually enough to confirm a person's diagnosis is said to be positive or negative for being infected with the SARS-CoV-2 virus. However, the presence of CT value PCR also plays an important role for the following reasons:
Predict the amount of virus in the body
The CT value can help doctors predict how much virus is in the patient's body.
As a rule of thumb, the lower the CT value or below 25–28, the more likely it is that the number of Corona viruses is increasing in the body. On the other hand, a high CT value or above 30–35 indicates that the number of viruses may be less.
However, until now there has been no research that can confirm the effectiveness or accuracy of the CT value PCR as a determinant of the amount of Corona virus in the body.
Monitor the progress of the patient's condition
In addition to diagnosing COVID-19, the PCR test and its CT value can also be used to monitor changes in the amount of virus present in a person's sample over time.
In hospitalized COVID-19 patients, the PCR examination usually needs to be repeated up to 2-3 times, i.e. from the initial diagnosis, during treatment, until when the patient has improved and can go home. Meanwhile, for patients who are self-isolating at home, it is sufficient to carry out a PCR examination once for the diagnosis of COVID-19.
In treated patients, the criteria for improvement or recovery were stated based on clinical conditions, namely improvement in symptoms experienced, as well as positive PCR results to negative, or at least an increase in CT value.
Helping doctors determine the steps for treating COVID-19
PCR and CT values can be used to predict the severity of COVID-19 disease. This examination also plays an important role in helping doctors to determine steps for handling and treating COVID-19 for patients, for example suggesting patients to self-isolate at home or refer patients to hospitals.
However, the CT value in the PCR test for COVID-19 cannot be used as the only benchmark for diagnosing COVID-19. To determine the severity and general condition of the patient, the doctor still needs to carry out a physical examination and supporting examinations, such as blood tests or chest X-rays.
In addition, the CT value in PCR also has another drawback, namely not being able to distinguish between live viruses that can infect other people and viruses that have died in the body.
So, even if you already understand the CT value of PCR, you should avoid interpreting the CT value yourself without valid information from a doctor, OK? If you still have questions about CT value PCR, you can ask the doctor directly through the ALODOKTER application