In this article, we will discuss the importance of CT value in Covid-19 Test. Ever since Coronavirus rampaged and created a havoc in the country, there is always a research and study going on to understand the level of Infection caused by this virus on a human body so that a preventive and curative measures can be taken effectively.

As of now, healthcare professionals are relying upon the RT-PCR test to determine the Covid positivity and uses a parameter called CT value to determine the severity of Infection. This value currently acting as a leading parameter to understand the viral load in a patient body.

What is CT Value

CT value is also known as Cycle Threshold value. It is a value emerges from RT-PCR tests which acts as a standard for detection of the SARS-CoV-2 coronavirus. The CT value of an RT-PCR reaction is the number of cycles at which fluorescence of the PCR product is detectable over and above the background signal.

In Simple words, CT value refers to the number of cycles after which the virus can be detected. If a higher number of cycles is required, it implies that the virus went undetected when the number of cycles was lower. The lower the CT value, the higher the viral load because the virus has been spotted after fewer cycles. More on Indian Express.

What is RT-PCR Test

RT-PCR is also known as Reverse transcriptase Polymerase Chain Reaction Test. In this test, a small sample of swab is taken from the test candidate from where RNA is extracted. It is then converted into DNS, which is then used to amplify specific sequences of the genetic material and diagnose if there is an infection. The swab can either be nasopharyngeal or oropharyngeal, which means it can be taken from both nose and throat.

Importance of CT Value in Covid-19 Test

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Till now, when a patient goes for Covid-19 testing, then hospitals or health care centers only provide the test result as Covid positive or negative. But now Doctors and Scientists are emphasizing on providing CT value as well along with the positive or negative report. This is because the CT count value is the one which determines the severity of the Infection and hence patient needs to be aware of that and can take appropriate measures with utmost seriousness as advised by their Doctors. More on PIB.

How CT value confirms Covid-19 Positivity

A patient is considered Covid-19 Negative if the CT value is 35 in the RT-PCR Test. If the CT value is below 35 in the RT-PCR Test, a patient is a Covid-19 positive. The lower the CT value, the higher the severity.

What ICMR Says About CT Value

According to the ICMR, a patient is considered Covid-19 positive if the Ct value is below 35. In other words, if the virus is detectable after 35 cycles or earlier, then the patient is considered positive. The ICMR has said lowering Ct threshold parameter may lead to missing several infectious persons. The ICMR has arrived at the Ct value of 35 based on laboratory experiences and inputs taken from several virology labs.

What's Globally Accepted CT Value

Globally, the accepted cut-off for Ct value for Covid-19 ranges between 35 and 40, depending on instructions from the respective manufacturers of testing equipment.

How CT Score is different from CT Value

• CT Score is the value taken from the Chest X-ray and CT Value is the count available from RT-PCR Test.
• In a chest Scan, the higher the CT score the higher is the severity of the Infection whereas in RT-PCR test, the higher the CT value, lesser is the chance to have severe Infection. No infection in the case of value above the threshold of 35.
• Chest CT score can predict the disease severity by showing the percentage of Lung Involvement whereas RT-PCR CT value provides the viral load on Covid-19 positive patient.