Partial relief at the Tor Vergata Polyclinic in Rome, where a suspected case of the new Omicron variant of Sars-CoV-2 was later revealed to be not Omicron, but an atypical Delta variant. Experts from the Capitoline facility urge people to keep their attention high for the risk of misleading diagnostic test results, such as for Omicron. “An unvaccinated patient admitted to the Respiratory Diseases Unit of the Tor Vergata Polyclinic – reads a note – has been positive for the first time in the molecular test from 25 November on two targets (E and RDRP gene / S gene), but negative several times to gene N, he then tested positive for Delta AY.4 variant with double atypical deletion “.
“The intuition of Professor Paola Rogliani, who is treating the patient – underlines from Tor Vergata the professor of Microbiology and Clinical Microbiology, Francesca Ceccherini Silberstein – was to request sequencing for a suspected atypical variant, such as the new Omicron . Thanks to the collaboration between the Virology Unit of the Polyclinic, directed by Sandro Grelli, and the Chair of Virology of the Department of Experimental Medicine of the Tor Vergata University, in less than 48 hours the sample was processed and the sequence obtained thanks to the work of the team, in particular of Maria Concetta Bellocchi and of the young undergraduates Greta Marchegiani and Daniele Stella. The result obtained showed Sars-CoV-2 with a Delta sublineage variant AY.4. On closer inspection, an infrequent deletion at position 214-215 of the nucleocapsid was identified by Mohammad Alkhatib, which may have resulted in the partially negative diagnostic test result. As in this Delta sublineage AY.4 variant, the Omicron variant also has an atypical deletion in the N gene that deserves attention, because it could have repercussions in the outcome and interpretation of diagnostic tests “.
“This aspect”, or rather the possible repercussions of atypical variants of Sars-CoV-2 on diagnostic tests, continues Ceccherini Silberstein, “will be investigated as soon as possible through collaborative studies within the recently funded European research project EuCare: European cohorts of patients and schools to advance response to epidemics’, led by Italy, dedicated to clarifying some of the crucial and most debated aspects of the epidemic “of Covid-19, such as” the impact of variants in serological and / or molecular tests and vaccines currently in use “.