Sudden emergence and rapid spread of COVID-19 created an inevitable need for expansion of the COVID-19 laboratory testing network across the world. The strategy to test-track-treat was advocated for quick detection and containment of the disease. Being the second most populous country in the world, India was challenged to make COVID-19 testing available and accessible in all parts of the country. The molecular laboratory testing network was augmented expeditiously, and number of laboratories was increased from one in January 2020 to 2951 till mid-September, 2021. This rapid expansion warranted the need to have inbuilt systems of quality control/ quality assurance. In addition to the ongoing inter-laboratory quality control (ILQC), India implemented an External Quality Assurance Program (EQAP) with assistance from World Health Organization (WHO) and Royal College of Pathologists, Australasia. Out of the 953 open system rRTPCR laboratories in both public and private sector who participated in the first round of EQAP, 891(93.4%) laboratories obtained a passing score of > = 80%. The satisfactory performance of Indian COVID-19 testing laboratories has boosted the confidence of the public and policy makers in the quality of testing. ILQC and EQAP need to continue to ensure adherence of the testing laboratories to the desired quality standards.

With the eradication of poliovirus, the focus has now shifted to environmental surveillance of poliovirus to determine the circulating polioviruses in an area. L20B and RD cell lines are used for isolation of polioviruses. It is imperative to study the efficacy of these cell line in isolating polioviruses from environmental samples. The present study was carried out to determine the sensitivity and specificity of L20B cell line for isolation of polioviruses from environmental samples. L20B and RD cell lines are used for isolation of polioviruses. Molecular characterization was done by using real time RT-PCR. A total of 432 sewage samples from Delhi and Punjab were processed for the isolation of polioviruses during Jan-Dec 2015. 96.76% of the samples were positive in either of the cell lines. Non-polio enteroviruses were obtained in 50 samples on primary isolation. On RT-PCR, 347 (94.29%) samples yielded polioviruses and the rest (21) non-polio enteroviruses or non-enteroviruses. A total of 703 isolates were obtained. 635 isolates were found polioviruses by PCR (90.33%), 20 isolates were found to be NPEV (2.84%) and 48 (6.83%) were found to be NEV. Out of the 20 NPEV isolates, 14 were from RLR (RD-L20B-RD) route and six isolates were from LR (L20B-RD) route. All 48 NEV isolates were from LR route. Thus L20B cell line is more sensitive as compared to RD cell line for isolation of polioviruses however it is not absolutely specific for polioviruses.

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Environmental surveillance of polioviruses has been used as an important tool in monitoring circulation of wild polioviruses and/or Vaccine derived polioviruses in sewage samples. It is important to distinguish Sabin like isolates from non-Sabin like; ELISA & dual stage real time RT-PCR have been used for the same. Current study was carried out on sewage isolates to compare ELISA & RT-PCR with sequencing to distinguish Sabin like from non-Sabin like. Out of 468 sewage specimens, 91 (19.44%) were non-polio enteroviruses positive and 377 (80.56%) were polio positive by virus isolation method. A total of 488 polio virus isolates were detected by L20B and RD route which were further subjected to ELISA and RT-PCR. The results were compared with sequencing. On comparison, the specificity of ELISA was only 66.67% in spite of very low sensitivity (3.43%). The sensitivity of RT-PCR was 97.71% which makes it a good primary screening test for detection of non-Sabin like viruses. However, the specificity was only 33.33%. RT-PCR appears to be a sensitive tool for detecting non-Sabin like viruses however; the isolates which are non-Sabin like by RT-PCR may not necessarily be mutated viruses. ELISA cannot be used for differentiation of Sabin likes from non-Sabin likes due to low sensitivity.