SGTF - isaric4c/wiki GitHub Wiki
Omicron has a deletion at position 69/70 of the spike protein which allows it to be tracked through S gene target failure (SGTF) in some PCR tests. Currently, approximately half of all tests conducted in the UK are able to detect SGTF. SGTF is not a 100% accurate test for Omicron and results are regularly evaluated against sequencing to ensure they are interpreted correctly. However, increases in SGTF can give a useful early indication of variant spread.
SGTF is a useful indicator of the presence of Omicron, because as a rule Delta cases have the S-gene and Omicron cases do not. However, it is not confirmatory as there are a number of other reasons that a sample might exhibit SGTF. For example, there are still a small number of cases of other variants, such as Alpha, in the UK which would also result in S-gene dropout or there is a lower amount of virus present in the sample where S-gene dropout cannot be confirmed.
Consult our own Metadata Catalogue for the SGTF main table.
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