What the Coronavirus Variants Mean for Testing – The New York Times

“You could face a situation where you just got unlucky with where you picked to target your test, and something popped up there that then made your test less efficient,” stated Nathan Grubaugh, a virologist at Yale University.The gene for the viruss particular spike protein, known as the S gene, has been especially prone to mutation, and tests that target this gene might miss out on particular variants. For example, Thermo Fishers TaqPath test fails to discover the altered S gene of the B. 1.1.7 variant, which was initially identified in Britain and is now spreading out quickly through the United States.But the test does not depend on the S gene alone; it has 3 targets and can still return accurate results by finding two other stretches of the coronavirus genome.Just 1.3 percent of molecular tests rely entirely on an S gene target, according to calculations carried out by Rachel West, a postdoctoral associate at the Johns Hopkins Center for Health Security. The rest either target more stable areas of the genome, which are less most likely to alter, or have multiple target series, which makes them less prone to failure. “Its extremely unlikely that youre going to get anomalies in all of them,” Dr. Lillis said.Updated April 15, 2021, 7:18 a.m. ETThe F.D.A. has noted 4 various molecular tests “whose performance could be impacted” by the versions, but notes that the tests must still work. When the virus has one specific anomaly and is present at extremely low levels, three of the tests have numerous targets; a fourth might be slightly less sensitive. (The four tests are the TaqPath Covid-19 Combo Kit, the Linea Covid-19 Assay Kit, the Xpert Xpress and Xpert Omni SARS-CoV-2, and the Accula SARS-CoV-2 Test.)”We do not believe that those four assays are significantly impacted,” stated Dr. Tim Stenzel, who directs the F.D.A.s office of in vitro diagnostics and radiological health. “It was more out of an abundance of care and transparency that we made that information public.”Antigen tests are less sensitive than molecular tests, however they are typically more affordable and quicker, and they are being deployed widely in coronavirus screening programs. These tests detect specific proteins on the exterior of the virus. Some genetic anomalies might change the structure of these proteins, allowing them to escape detection.

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