West Bengal starts ‘Pool Test’ to track asymptomatic COVID-19 patients

As number of asymptomatic Corona patients are rising in India, West Bengal government has decided to start pool testing samples in low-risk zones which have reported 2% or lesser Covid-19 positive cases. This method will involve pooling in samples of five possible suspects, even though they are asymptomatic, and testing them together. A negative result will prove that all five samples in the pool are negative and a positive result will prompt further tests of all five samples individually.

Indian Council of Medical Research (ICMR) director-general Balaram Bhargav had in a letter to all states, including West Bengal proposed pool testing to ramp up surveillance. A feasibility study at the Virus Research and Diagnostic Laboratory (VRDL) at King George’s Medical University, Lucknow, had clearly demonstrated that performing real time PCR tests (polymerase chain reaction tests which detects Covid-19 antigens in the body) by pooling five samples show desired results in places where the rate of incidence is low. The ICMR advisory said all five individual samples in a pool which had tested negative would be considered negative, and any positive pool would lead to individual samples being tested. 

In a circular published recently, the state government said it has decided to adopt the pool-testing method. Pool tests in Bengal will be carried out only in those zones which have a low prevalence rate of infection as per the community survey and surveillance among asymptomatic individuals. Bengal will not conduct pool tests in zones where people may have come in contact with a known Covid-19 positive patient and where the rate of infections could be high. As per ICMR guidelines,

Pool Tests will also not be done for healthcare workers who are in direct contact with Covid-19 patients. In zones, which have a prevalence rates of over 5%, pool tests have not been recommended.