NEW YORK – Roche last week launched a respiratory virus test that detects 12 targets using Temperature-Activated Generation of Signal (TAGS), a new PCR technology developed at the company.
The Cobas Respiratory Flex test runs on the Cobas 5800, 6800, and 8800 PCR instruments and can detect up to 12 respiratory viruses from nasopharyngeal swab specimens: influenza A and B, respiratory syncytial virus, adenovirus, human metapneumovirus, enterovirus/rhinovirus, parainfluenza 1 to 4, SARS-CoV-2, and other coronaviruses.
The assay has been launched in countries accepting CE marking and Roche plans to submit it to the US Food and Drug Administration for 510(k) clearance in the fourth quarter of this year.
Igor Kozlov, head of reagent research and design at Roche Diagnostics Solutions and one of the technology's inventors, noted that TAGS is the "next step" in standard TaqMan PCR assays, which are currently used in all of Roche's high-throughput PCR instruments. Standard TaqMan assays use fluorescent reporters that release a fluorescent dye if a target is present in a sample. The multiplexing capabilities of TaqMan assays are "limited," he said, as standard tests use five fluorescent dyes — one control and four for the target DNAs being measured.
The TAGS technology was developed to expand multiplexing in a single PCR reaction beyond four targets for syndromic panels, Kozlov said. "Patients can have very similar symptoms caused by different viruses, and doctors have a hard time diagnosing these diseases based on symptoms," so there is a "need to run a big panel," he said.
The new technology allows the detection of up to 15 targets per test. Standard assays are based on optical channels and are limited by the five optical channels used in PCR, but TAGS has introduced "a temperature dimension," Kozlov explained. The technology uses standard reporters that are activated at low temperatures and are found in Roche's existing PCR tests. To that, it adds two sets of reversible thermo-activated reporters that can only be visualized at medium and high temperatures. At a lower temperature, those dyes can no longer be seen, and the signals disappear.
Although there is no published data on the performance of the Cobas Respiratory Flex test, when compared to 510(k)-cleared and CE-marked comparators, it reached a positive percent agreement of at least 95 percent for all viruses except enterovirus/rhinovirus, which had a PPA of 84 percent, according to the assay's user manual. The test reached a negative percent agreement of at least 96 percent for all viruses. A total of 1,306 samples were evaluated in the comparator study.
By utilizing the existing optical channels and adding a temperature component, Roche has been able to increase multiplexing without having to change its instruments or consumables, Kozlov noted. TAGS technology can be used on existing Roche high-throughput instruments with the same consumables as its other tests, but the reagents are formulated differently, he said. The software included with the tests does need to be changed, because every PCR cycle requires the capture of five images at three different temperatures rather than five images at the same temperature.
The data processing software will also be different because it must process 15 signals rather than five, he noted.
Another benefit of the new technology is the test's reflexing capability. Customers can run the test for all 12 viruses and choose which results they want to see. For example, a customer could run the test and receive results only for influenza A/B, but if those results were negative, the user could do a digital reflex test and reprocess the data to see the results for other targets without having to run the test again, Kozlov said. This "gives a lot of flexibility for customers," he added.
The company interviewed customers to determine which targets were most medically relevant and which could be combined in subgroups for the Respiratory Flex test, Kozlov noted. For example, the test combines four coronaviruses — 229E, OC43, NL63, and HKU1 — into one broader coronavirus group for detection.
The TAGS technology is "universal" and has opportunity for use in other diseases beyond respiratory ones, he said, including syndromic panels or viral panels that require viral genotyping.
It is also applicable to all PCR instruments that use optical detection and thermocycling, not just high-throughput instruments, Kozlov noted.
He added that the new technology is an "enhancement of the standard that brings a new capability" and will be particularly accessible because it can be used with Roche's existing installed base of instruments that significantly expanded during the COVID-19 pandemic. TAGS will allow Roche to bring "this syndromic testing to a much broader number of patients," he said.