Kits Miss Omicron In US, Show False Negatives Docs urge ICMR to check testing kits

Docs urge ICMR to check testing kits

Kits Miss Omicron In US, Show False Negatives

Pushpa.Narayan@timesgroup.com

Chennai:22.12.2021

Days after the USFDA warned that some testing kits in their country were throwing “false” negatives, particularly among those carrying the omicron variant, infectious diseases experts here have asked the Indian Council for Medical Research (ICMR) to review all testing kits, including indigenously manufactured products for its accuracy.

SARS-CoV-2, the virus that causes Covid-19, has mutated over time, resulting in genetic variations. “We don’t know much about the new variant Omicron, except that it spreads rapidly, increases hospitalisations and deaths. Now, we are learning that tests including gold standard ones are affected by viral mutations,” said infectious disease expert Dr Subramanian Swaminathan of Gleneagles Global Hospitals. “The ICMR should check all the testing kits and permit only the ones that are accurate. With false negatives, isolation norms will be relaxed, and risk of transmission will increase,” he said.

The new variant is already straining the testing capacity of several countries. With people queuing up for pre-travel tests, the spike in Covid-19 cases in several European countries has increased the number of daily tests. States like Tamil Nadu haven’t allowed home tests or antigen tests too. The strain here will be much more when cases increase. The state conducts around one lakh RTPCR tests a day acros 317 labs.

“Molecular tests that use multiple genetic targets to determine a result are less likely to be impacted by increased prevalence of genetic variants,” said virologist Dr T Jacob John. “The ICMR and The Indian SARS-CoV-2 Genomics Consortium should check kits, antigen, PCR and home tests used across India. Until then clinicians should consider results in combination with clinical observations, patient history, and epidemiological information,” he said.

The state public health laboratory says it uses the True-Nat system, which is now a comprehensive assay for screening and confirmation of COVID-19 cases. The RT-PCR tests are conducted in whole for all the genes - N’, ‘S’, ‘E’ and ‘ORF'. The S gene is absent in Omicron. "Since S-gene is not detected during the test, it is called S-gene dropout,” said state DPH laboratory head Dr S Raju. S-dropout is considered as a proxy indicator for the new variant. “And it also shows that the tests are effective,” he said. Nevertheless, public health officials admit not all labs in the state use the same kind of kits.

DISCOMFORT: Healthcare official collecting a nasal swab for Covid testing in Madurai