Ct (cycle threshold) worth signifies the variety of cycles accomplished to determine the virus in a pattern throughout an RT-PCR take a look at. This worth is inversely proportional to the viral load within the pattern — decrease the worth, increased the viral presence.
Final week, the state wrote to the Indian Council of Medical Analysis (ICMR) asking if the Ct worth cut-off will be at 24 (which meant a pattern testing over 24 will be described as damaging). The ICMR responded by saying it can’t be decrease than 35.
Dr Balram Bhargava, director common of ICMR, in a letter to state well being secretary Dr Pradeep Vyas, mentioned a Ct worth of lower than 35 must be thought-about as a Covid-19 constructive case, primarily based on a consensus derived from completely different laboratories within the nation. Dr Bhargava wrote that implementing a Ct worth cut-off of 24 will result in “lacking of a number of infectious sufferers and elevated illness transmission.”
Well being minister Rajesh Tope informed TOI that it has now been determined that these with a Ct worth over 35 might be declared Covid-negative. He, nevertheless, didn’t reply to a question on why Maharashtra had sought a clarification on the Ct worth within the first place.
Dr Shashank Joshi, a member of the state Covid-19 process drive, mentioned there shouldn’t be an over-reliance on the Ct worth whereas treating sufferers. It is solely helpful as a diagnostic cut-off and has been reassessed over the previous one 12 months, he mentioned. Initially, the ICMR had fastened the brink at 40 and now it has been revised to 35. “It doesn’t have any relevance for public well being or scientific use,” Joshi mentioned.
He mentioned, “The speedy antigen checks come again damaging for CT worth between 24 and 35. We have to do an increasing number of RT-PCR checks. When there’s a giant inhabitants of asymptomatic sufferers concerned, the query is whether or not they are often spreaders or not. There’s a chance they are often. Decreasing the brink will scale back the so-called ‘case-demic’. On the identical time, those that want care must be quarantined and handled. The thought is to get the suitable inhabitants.”
Dr Suhas Pingle, former IMA (Maharashtra) secretary, mentioned different elements, moreover simply the Ct worth, must be thought-about whereas treating Covid sufferers.
“As clinicians, we take into account a affected person’s premorbid situation, age, signs and severity of an infection. The RT-PCR is a diagnostic software. From the general public well being perspective, the speedy antigen is an efficient screening take a look at, however it additionally throws up a excessive variety of false negatives. The RT-PCR checks are achieved when somebody is available in with a chilly, cough, fever or associated signs,” he mentioned.