With COVID-19 pandemic, individuals across the world are becoming increasingly familiar with scientific terms. One such term that now becomes element of the public vocabulary is ‘Ct value’ which is indicated in RT-PCR tests which assist to identify regardless of whether a patient is COVID-19 positive or not.
Today’s IE’s report refers to how the Maharashtra government had lately sought clarity from the Indian Council of Medical Research (ICMR) to have an understanding of regardless of whether it is advisable to go forward with treating a individual as Covid-adverse if the Ct worth exceeds 24 and the individual appears to be asymptomatic.
Given that the ICMR documents indicated distinct Ct values and divergent views had been emerging on the exact same, the state had requested for clarity on the course of action to be taken with regard to the Ct worth.
After taking inputs from numerous virology labs, the ICMR DG responded to the state’s query and wrote to its Health Secretary. According to the IE report, ICMR had advised that all these patients with Ct worth much less than 35 may well be deemed as positive and these with Ct worth more than 35 may well be deemed as adverse.
RT-PCR tests: What is Ct worth?
When taking the RT-PCR test, Ct worth is taken into consideration. A Ct worth refers to the quantity of cycles following which the virus can be detected. If a greater quantity of cycles is needed, the implication is that the virus was undetected when the quantity of cycles was on the decrease side. The decrease the CT worth, the greater is the viral load as it also indicates that the virus has been spotted following fewer cycles.
RT-PCR tests: Why is CT-worth essential?
According to the ICMR, a patient is deemed Covid-positive if the Ct worth is below 35. Simply place, if the virus is detected following 35 cycles or prior to it, a patient is deemed as positive.
Suppose this benchmark is lowered to 24 — which is the worth described by Maharashtra in its letter to ICMR even though looking for clarity on the matter — it would imply that Ct values in the 25-34 variety would not be deemed as positive.
Therefore, a benchmark of 35 indicates that more patients would be treated as becoming COVID-19 positive than if the benchmark had been 24. Lowering the Ct threshold parameter may well lead to missing a number of infectious persons, according to ICMR.
The IE report cites major virologist Dr Shahid Jameel, Director of Trivedi School of Biosciences, Ashoka University as getting stated that one can take into consideration Ct worth as a measure of transmission possible.
Significance of the ICMR threshold of 35
Worldwide, the accepted Ct worth reduce off for Covid-19 is involving 35 and 40, topic to guidelines from respective producers of the testing gear. The ICMR has indicated the Ct worth of 35 based on input that have been taken from a number of virology labs.
While the ICMR has issued no new advisory, it has informed the Maharashtra government that it is not advisable to use a decrease cycle threshold parameter. The danger is that such a move would lead to missing a number of infectious persons and improve illness transmission, according to Dr Balram Bhargava, ICMR’s DG, who has been quoted by IE in its report.
Correlation involving a Ct worth and severity of illness
Citing Dr Parikshit Prayag, consultant for infectious illnesses at Deenanath Mangeshkar Hospital in Pune, IE’s report has quoted his insights on the exact same:
1. Ct worth does not correlate with severity
2. It correlates only with infectivity.
3. From the infectivity point of view, it can matter, not severity
It is also pertinent to take into consideration that a number of components are essential even though interpreting an RT-PCR test. Also, the RT-PCR test final results may well additional rely on the precise system of specimen collection and the time from the point of infection to its collection and then evaluation.