New Delhi: As the Ministry of Health and Family Welfare continued to insist that India had an adequate supply of test kits, the Indian Council of Medical Research has advised a unique testing strategy in specific clusters that will ration the number of RT-PCR kits but also be able to conduct more tests in lesser times.
The ICMR, on Monday, recommended the use of "pooled samples" in view of the urgent need to ramp up testing numbers due to COVID-19 cases in the country "rising exponentially".
This method involves putting a sample containing specimens of multiple individuals through PCR screening and then conducting individual RT-PCR if the collective tests positive. According to the ICMR, when such a sample tests negative, it can be regarded that all individual specimens in the sample are negative for SARS-CoV-2.
However, studies conducted by ICMR labs in Lucknow, show that when 5 individual samples are pooled, this method can be feasible only for areas with low positivity rates and when individual samples are asymptomatic and do not have any travel or contact history.
In such conditions, the studies found that if a pool of 5 samples tested positive, individual testing is recommended and if it tests negative, it can be regarded that all samples are negative.
As per the ICMR's recommendation, if such a method is adopted, individual RT-PCR tests will not be required for pools that are found negative and would be used only for pools that test positive. Another advantage of this method is that it will also increase testing among asymptomatic individuals - who may become transmitters if untested.
On Saturday, Tamil Nadu Chief Secretary had said that India's first batch of Rapid Antibody Test Kits had been diverted to the US. On the same day, ICMR invited bids for 25 lakh RT-PCR Test kits and 45 lakh Antibody Test Kits.
The ICMR's recommendations say that this method is advisable in areas with less than 2 per cent positivity rate with an eye on the increase in this rate. As for areas with positivity rates between 2 and 5 per cent, the ICMR recommends this method be used only for community surveillance among asymptomatic individuals with no travel history or contact history with lab-confirmed cases or health care workers in direct contact with COVID-19 patients. These people would anyway have to be tested individually, the ICMR said, adding that this strategy was not for areas with positivity rate above 5 per cent.
However, if more than five (5) specimens are pooled, the samples might become susceptible to false negatives because this might lead to the dilution of the viral load.