In July, the discussion on setting a new limit for the cycle threshold (CT) for Covid-19 cases abound in Malaysia. The Malay equivalence 'Nilai Kitaran Ambang' is often quoted. I am glad the concept of threshold (ambang) is fast becoming a household name. Below is an excerpt from The Star:
"The cycle threshold (termed Ct value) is the number of amplification cycles required for the fluorescent signal to cross a certain threshold.
The number of cycles it takes to reach this level provides an estimate of the viral load which is equated with the severity of the infection.
The lower the Ct value the greater the amount of RNA (genetic material) there is in the sample. The higher the cycle number, the less RNA there is in the sample.
A standard RT-PCR usually goes through 35 cycles, which means that by the end of the process, billions of new copies of sections of the viral DNA are created from each viral strand present in the sample."
Image credit - The Center for Evidence-Based Medicine
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