The government has decided to use one time RT-PCR based pooled sampling for Covid-19 screening among migrant workers and returnees from abroad kept in quarantine facilities.
The same testing technique would also be used for monitoring in green zones districts which have reported no cases till now or in the last 21 days, the Union Health ministry said while issuing 'Guidelines for RT-PCR based pooled sampling for migrants/returnees from abroad/green zones' on Thursday.
"A decision has been taken to use one time RT-PCR based pooled sampling for surveillance purposes for migrant workers in institutional quarantine facilities, international passengers in institutional quarantine facilities/hotels earmarked for quarantine and for surveillance purposes in green zones (districts with no case/no case reported in last 21 days)," the guidelines stated.
According to the guidelines to be followed for pooling of samples, a cohort of 25 people will be identified, and throat/nasal swab will be collected as per the laid down protocol by trained laboratory personnel wearing appropriate protective gear such as apron, hand glove, face-shield/goggles and N-95 mask.
Proper labelling (name/age/gender/specimen ID) needs to be done on specimen container, it said.
The guidelines stated that 25 such samples of such cohort would be packed in triple layer packaging and will be transported to the identified laboratory under cold-chain as per ICMR guidelines.
The outer container mentioning "be tested for SARS-CoV-2" will also bear the details of sender (name/address/phone number). The samples will be aliquoted and thereafter pooled samples from 25 specimens shall be tested in the laboratory by RT-PCR method.
The report will be conveyed to the quarantine/concerned facility within 24 hours.
"If any of the pooled samples tests positive, individual samples would be tested from the aliquoted samples preserved in the laboratory," it said.
A pooled testing algorithm involves the PCR screening of a specimen pool comprising multiple individual patient specimens, followed by individual testing only if a pool screens positive.
According to the advisory issued by ICMR on April 13, all individual samples in a negative pool should be regarded as negative.
The sample pooling for real-time RT-PCR screening for Covid-19 is only recommended in areas with low prevalence of Covid-19 (initially using proxy of low positivity of less than 2 per cent from the existing data.
The death toll due to Covid-19 rose to 2,549 and the number of cases climbed to 78,003 on Thursday registering an increase of 134 deaths and 3,722 cases in the last 24 hours till Thursday 8 AM, according to the Union Health Ministry.