ICMR Rejects Maharashtra Plea To Revise Covid Test Criteria
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Facing an unprecedented surge in Covid-19 cases, Maharashtra had requested the Centre to revisit the norms for Covid testing that decide whether a person is positive or negative. The Indian Council of Medical Research (ICMR), has now written back saying the proposed revision in positivity criteria will cause too many infections to be missed and increase the transmission of the disease further.

According to the research body, the current positivity criteria is based on the cycle threshold (Ct), which is a measure of how soon after an RT-PCR test the SARS-CoV-2 is detected in a sample. As the samples move through cycles, the sooner the virus is detected, the higher the viral load is supposed to be. 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 sigmoidal real-time RTPCR curve is acceptable,” ICMR Director General and Secretary, Health Research, Dr Balram Bhargava wrote in a letter to Maharashtra Principal Secretary (Health) Dr Pradeep Vyas. “All patients with a Ct value of less than or equal to 35 may be considered as positive while those with Ct value greater than 35 may be considered as negative.

All samples with CT value less than or equal to 35 a poor sigmoidal curve should be essentially retested. Implementing a Ct value cut-off of 24 is not at all advisable as this would lead to missing of several infectious patients and increase disease transmission,” he added. 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.

However, Vyas said the Maharashtra government did not seek a change to the Ct value. “We never requested GoI to reduce CT value, [we] requested to clarify as it appeared different labs and different states were adopting different practices. The state only wanted to know in view of different standards in different documents of ICMR,” he told.

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