Study population and setting
This retrospective cohort study included two cohorts (a primary care cohort and a critical care cohort) of patients diagnosed with COVID-19 in England who had available data on S gene target failure (SGTF) status, a proxy for the B.1.1.7 mutation. Results from COVID-19 testing in England are reported to Public Health England, including molecular diagnosis of SGTF, which was defined as non-detectable S gene and cycle threshold less than or equal to 30 for N and ORF1ab target. The primary care cohort included 198,420 who tested positive for SARS-CoV-2 in the community between November 1, 2020 and January 26, 2021 who were followed to investigate the association between SGTF and receipt of critical care or death due to COVID-19 (confirmed or suspected) within 28 days of the positive COVID-19 test. The critical care cohort included 3,452 individuals who tested positive for SARS-CoV-2 in the community between November 1, 2020 and January 27, 2021 and who received critical care. This cohort investigated the association between SGTF and duration of organ support, (e.g. respiratory, cardiovascular, renal, liver, or neurological support), duration of critical care, and mortality at the end of critical care.
Summary of Main Findings
59.4% of individuals in the primary care cohort had SGTF. In analyses adjusting for demographics, comorbidities, and date of positive test, the hazard ratio for mortality for the SGTF group vs. the non-SGTF group was 1.59 (95% CI: 1.25-2.03) and for critical care admission was 1.99 (95% CI: 1.59-2.49). Results were consistent among individuals with at least 28 days of follow-up (mortality endpoint) or 20 days of follow-up (critical care endpoint). Among the 3,452 individuals included in the critical care cohort, 58.5% had SGTF and 822 (24%) died during the study period. After adjusting for confounders, SGTF was not associated with mortality or other indicators of COVID-19 severity among those already in clinical care.
This was a large study drawing on validated and broadly representative data sources in England.
The study population included in each analysis was not well described, and only about half of potentially eligible participants (people tested in the community) had SGTF status available. If SGTF results were not missing randomly, this could bias the results. SGTF was used as a proxy for the B.1.1.7 mutation: though the authors report that >99% of SGTF during the study period were due to B.1.1.7, this was not confirmed with sequencing data. The study population included only individuals who were tested for COVID-19 in the community, and it is unknown whether the association between SGTF and outcomes among individuals in critical care who were first tested at the hospital differs from those tested in the community.
This study adds to growing literature about increased severity of COVID-19 due to SGTF, a proxy for the B.1.1.7 SARS-CoV-2 variant, and is the first to explore disease outcomes related to SGTF among patients receiving critical care.