TY - JOUR T1 - The association between SARS-CoV-2 RT-PCR cycle threshold and mortality in a community cohort JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.00360-2021 VL - 58 IS - 1 SP - 2100360 AU - Rupert Waudby-West AU - Benjamin J. Parcell AU - Colin N.A. Palmer AU - Samira Bell AU - James D. Chalmers AU - Moneeza K. Siddiqui Y1 - 2021/07/01 UR - http://erj.ersjournals.com/content/58/1/2100360.abstract N2 - A coronavirus disease 2019 (COVID-19) diagnosis is widely made by the use of reverse transcription polymerase chain reaction (RT-PCR) testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). When using RT-PCR, the infectivity of SARS-CoV-2 can be inferred from the threshold cycle (Ct) value [1]. It is best practice to confirm the validity of the standard curve using reference materials or in-house plasmid controls with known viral copy numbers [2]. As the Ct value represents the cycle number at which the signal breaches the threshold for positivity, a lower Ct value is indicative of a higher viral load. Although some studies suggest that viral load is associated with mortality and infectiousness [3, 4], a systematic review has identified little difference in viral load between pre-symptomatic, asymptomatic and symptomatic patients [5]. As a result, the clinical relevance of viral load remains controversial, and it is not used in clinical practice [6]. Here, we report the relationship between the Ct value and all-cause mortality for people who tested positive for SARS-CoV-2 on a combined nasal and pharyngeal swab in the Tayside region of Scotland, UK. This is a community cohort study and includes the local population of the region, as well as symptomatic health and social care workers tested as part of a screening programme [7]. In order to obtain clinical characteristics and outcomes for those who tested positive, anonymised record linkage was conducted between routine healthcare datasets as described previously [8]. All positive PCR tests from 12 March until 1 May, 2020 were included, and all deaths recorded by National Records Scotland until 20 May, 2020. Approval for anonymised data linkage was granted by the local Data Protection Officer (Caldicott Guardian).Ct values from RT-PCR tests are associated with risk of mortality in SARS-CoV-2 infection. Hazards of Ct values <20 compared to >30 were 2.20 (95% CI 1.28–3.76) in a model adjusted for age, sex, comorbidities and hospitalisation. https://bit.ly/3gjuqdU ER -