What does the CT Value in a Covid-19 Test Mean?

 CT is a value that you receive during the RT-PCR tests. It is the gold standard for the detection of Covid-19. So how does this work? Well to conduct this test, first and foremost RNA is needed, which is collected from swabs generally from the nose and throat. Then this RNA is converted to DNA for amplification. This amplification increases the ability of the test to detect the presence of the virus. The CT value assists the presence of the virus and the strength or severity of the virus by the valuation of whether the virus was detectable in 35 cycles or not. 

Now let’s look at some common queries associated with the CT Value. 

What does CT value signify?

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. According to ICMR, what is considered Covid positive, is when the virus was detectable before or within 35 cycles. 

Is there any correlation between a Ct value and the severity of the disease?

According to ICMR, there is no significant correlation between the CT value and the severity of the disease. But, that’s not all even if there is no impact on the severity of disease,  the effect is significant on the infectivity or communicability. A person with a high CT value covid result is more likely to affect people around with the virus, said Dr. Parikshit Prayag.

Is the CT Value always correct?

Well, not always but not because the test is faulty, mostly because of mishandling of the sample. The test results can be affected by poor collection, the temperature of transportation, and the time duration between the collection to the receipt. All this hampers the strength of the RNA which results in misinterpretations while testing.

Do people with the severity of disease always report a low CT value?

This goes case by case. Generally speaking no, patients in the early symptomatic phase may show a high CT value, the asymptomatic patient may show CT values that are similar to the ones with a severe attack of virus. So, what actually plays a significant role here is the host factor, and that varies from person to person. 

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