How has COVID-19 RT-PCR testing evolved with emergence of Delta and Omicron?

The Indian Council of Medical Research (ICMR) has approved Tata Medical's indigenously made quick RT-PCR testing kit to detect the highly mutant coronavirus variant Omicron.   
 
In parallel to the evolution of coronavirus, RT-PCR testing in India has also gradually evolved in last two years, aimed at faster detection of the emerging variants. The quick results help the government conduct genome sequencing which further tells the which is the variant largely circulating in the country. Genome sequencing has gained further significance after the emergence of Omicron threat. 
 
When the COVID-19 pandemic hit the country, the Reverse Transcription Polymerase Chain Reaction (RT-PCR) was recommended for detecting the SARS-CoV-2 virus. The gene-based RT-PCR test uses Real-Time Reverse Transcriptase (RT)-PCR Diagnostic Panels for detecting the presence of viral RNA through swab samples. The samples are analyzed for reagents to identify the presence of the virus.  
 
"With the evolving pandemic, we have also improved the RT-PCR testing. Initially, only one gene was targeted to check the presence of SARS-CoV-2. Later when Delta variant started circulating in India, the RT-PCR kits targeted two mutated genes to detect the Delta variant. Tata kit that we recently approved uses a three gene detection," said a senior scientist at ICMR. 
 
The Tata MD COVID Express RT-PCR solution consists of Tata MD CHECK XF, a 3-gene RT-PCR kit that is RNA extraction free and uses fast amplification protocol combined with a portable and fast qPCR analyzer. The solution has a processing time of just one hour and can process 30 samples per batch per machine. The kit is approved by ICMR with 95 per cent+ sensitivity and 100 per cent specificity. Similar to the previous RT-PCR tests, it is faster and targets omicron. 
 
Tata MD CHECK RT-PCR Fast 3Gene is a 3-Gene RT-PCR kit that uses fast amplification protocol and hence has a processing time of 90 minutes. It can process 90 samples per batch per machine. The kit can be used in existing qPCR instruments. It is approved by ICMR with 100 per cent sensitivity and 100 per cent specificity. 
 
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Both these kits use three-genes that are variant proof. Another key advantage of the above solution is its high throughput feature. Tata MD XF with a portable and fast qPCR analyzer can processes 300-400 samples in 2 hours using five lines. Tata MD CHECK RT-PCR Fast 3Gene using 5 qPCR instruments (96 wells) can process 450 samples in 2 hours. The prevalent faster testing solutions currently being used in airports process one test at a time with low throughput capacity and are yet very expensive. 
 
"These express testing solutions can be applied in multiple areas where quick, high volume, and reliable testing is required such as airports and events," Tata Medical and Diagnostics Ltd CEO Girish Krishnamurthy said. 
 
"The Tata MD CHECK Express PCR testing solution has been proven to deliver rapid and dependable results in a real-world environment with a high volume of tests at the Kempegowda International Airport, Bengaluru since early this month. It has proved instrumental in helping to address the rush of fliers from 'high risk' countries required to undergo mandatory RT-PCR testing," he said. 
 
India has been gradually reducing the use of another type of COVID-19 testing called as rapid antigen testing, which is also done with samples collected from nose or throat with a swab. Even though its results are available within 30 minutes, the test is not considered accurate as it may not detect the important proteins of the SARS-CoV-2 virus in the initial stages. Further, it can also not find out the variant. 
 
With the Omicron variant resulting in a further surge of cases across the globe, India is back on high alert with international passengers from high-risk countries requiring mandatory testing as well as random testing of passengers from other countries.  
 
Some states have also introduced restrictions with the requirement of negative COVID tests for domestic passengers. In addition, with studies in India pointing to a possible surge in cases in February next year, there is expected to be a multiple fold increase in demand for RT-PCR COVID tests that are economical and give fast results.  
 
India in last 24 hours conducted a total of 11,54,302 tests. India has so far conducted over 68.24 crore (68,24,28,595) cumulative tests.

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