“You would run right into a state of affairs the place you simply bought unfortunate with the place you selected to focus on your check, and one thing popped up there that then made your check much less efficient,” mentioned Nathan Grubaugh, a virologist at Yale College.
The gene for the virus’s attribute spike protein, often called the S gene, has been notably susceptible to mutation, and assessments that concentrate on this gene might miss sure variants. For example, Thermo Fisher’s TaqPath check fails to detect the mutated S gene of the B.1.1.7 variant, which was first recognized in Britain and is now spreading quickly by the US.
However the check doesn’t depend on the S gene alone; it has three targets and might nonetheless return correct outcomes by detecting two different stretches of the coronavirus genome.
Simply 1.3 % of molecular assessments rely solely on an S gene goal, in line with calculations carried out by Rachel West, a postdoctoral affiliate on the Johns Hopkins Heart for Well being Safety. The remaining both goal extra steady areas of the genome, that are much less more likely to mutate, or have a number of goal sequences, which makes them much less prone to failure. “It’s not possible that you simply’re going to get mutations in all of them,” Dr. Lillis mentioned.
The F.D.A. has listed 4 totally different molecular assessments “whose efficiency could possibly be impacted” by the variants, however notes that the assessments ought to nonetheless work. Three of the assessments have a number of targets; a fourth could also be barely much less delicate when the virus has one specific mutation and is current at very low ranges. (The 4 assessments are the TaqPath Covid-19 Combo Package, the Linea Covid-19 Assay Package, the Xpert Xpress and Xpert Omni SARS-CoV-2, and the Accula SARS-CoV-2 Check.)
“We don’t assume that these 4 assays are considerably impacted,” mentioned Dr. Tim Stenzel, who directs the F.D.A.’s workplace of in vitro diagnostics and radiological well being. “It was extra out of an abundance of warning and transparency that we made that data public.”
Antigen assessments are much less delicate than molecular assessments, however they’re sometimes cheaper and quicker, and they’re being deployed broadly in coronavirus screening packages. These assessments detect particular proteins on the surface of the virus. Some genetic mutations may change the construction of those proteins, permitting them to flee detection.