The Indian Council of Medical Research rejected the Maharashtra government’s request to reduce the Cycle Threshold (CT) value cut-off.
The new wave of Covid-19 cases has caused stress and panic among the countrymen as well as political leaders. The hardest-hit state of this new wave is Maharashtra which is home to India’s financial center-Mumbai.
Facing this unprecedented surge in cases, the Maharashtra government had requested the centre to reevaluate the norms for covid testing which determine whether a person is “positive” or “negative.” However, the request was rejected by the ICMR which wrote back and said that any revision in positive criteria will cause many infections to be missed, hence greatly increasing the transmission rate.
“ICMR has taken inputs from different virology laboratories across the country to arrive at a single Ct value cut-off based on individual laboratory experiences. As per uniform consensus, a Ct value cut-off of 35 with a good sigmoid real-time RTPCR curve is acceptable,” Dr. Balram Bhargava, Director General and Secretary, Health Research wrote in a letter addressed to Maharashtra Health Secretary
In response, Bhargava wrote that the globally accepted cut-off for CT value for Covid-19 ranges from 35-40, depending upon the instructions laid down by individual manufacturers.
Asking for reduced CT value (from 35 to 25) to declare patient negative is dangerous. Doing so will make several patients with low virus load "negative" and they will be super-spreaders. This is not the way you control pandemic Shri @OfficeofUThttps://t.co/2U3cKQjXCC— Dr Vijay Chauthaiwale (@vijai63) April 8, 2021
The Maharashtra government had requested the centre to reduce the CT value cut-off from 35 to 24 for positivity rate under the RT-PCR test and also requested the centre to reduce the CT value so that fewer patients come under positive category.
What is the “CT” Value?
The CT value or Cycle threshold determines the severity of the Covid-19 Infections. The lower CT value indicates higher severity while the higher CT value indicates lower severity. If the CT value is above 35, the patient is deemed as “covid negative” meanwhile if the CT value is lower than 35, the patient is considered “covid positive”
“CT refers to the number of cycles needed to amplify viral RNA to reach a detectable level” according to the American Association for Clinical Chemistry.
Specimens with lower CT values generally have more viral RNA than those with higher values, suggesting the severity of the COVID-19 infection. The CT value thus could flag off at-risk patients and prioritise them for contact tracing.