MADURAI: Tamil Nadu will be commencing a state-wide serosurveillance study on COVID-19 exposure in a week, TN health secretary Dr J Radhakrishnan told The New Indian Express on Tuesday.
The ICMR is conducting its own serosurveillance across the country in which samples from TN are also tested. Considered the gold standard to measure recent or past exposure to infectious diseases, sero surveillance study is conducted to ascertain the antibody levels produced against the infection by testing blood (serum or plasma) samples.
Of the 60,000 blood samples to be collected from all the districts, nearly 30,000 would be tested for the antibodies in the first phase, beginning this month, said Radhakrishnan.
Sources in the Directorate of Public Health and Preventive Medicine said the samples would be tested through chemiluminescence immunoassay (CLIA), a technique using light emission caused by a chemical reaction. A total of 26,640 samples identified in 888 clusters – comprising 30 adults in each – across the State are to be a part of the study, they added.
Managing director of Tamil Nadu Medical Services Corporation (TNMSC) Dr P Umanath said that the TNMSC, which does not directly procure the CLIA equipment, has issued orders to five vendors for the installation of the imported equipment, costing around Rs 20-25 lakh each. The State would only bear the cost of the test, he added.
The samples would be sent to one of the six identified cities – Madurai, Tirunelveli, Coimbatore, Chennai, Tiruchy and Salem – where the equipment would be installed, said Umanath.
Deputy Director of Health Services (Madurai) Dr K V Arjun Kumar said that 1,140 samples from 38 identified clusters would be collected in the Madurai district during the first phase. The samples from Theni, Dindigul, Virudhunagar, Pudukkottai and Madurai districts would be tested at Samayanallur Primary Health Centre, where the CLIA equipment is installed, he added.
Well-trained laboratory technicians, health inspectors and staff nurses would be engaged in doorstep sample collection in identified villages and wards for the three-week-long survey, for which health department staff would receive training this week.
Notably, a sero-survey, first conducted by the Greater Chennai Corporation in July, revealed that one-fifth of the city population was infected. A second serosurvey in Chennai will begin soon.