SARS-CoV-2 Viral load at presentation to hospital is independently associated with the risk of death

Tanner, Alex R; Phan, Hang; Brendish, Nathan J; Borca, Florina; Beard, Kate R; Poole, Stephen; W Clark, Tristan

Objectives: Previous studies have suggested that SARS-CoV-2 viral load, measured on upper respiratory tract samples at presentation to hospital using PCR Cycle threshold (Ct) value, has prognostic utility. However, these studies have not comprehensively adjusted for factors known to be intimately related to viral load. We aimed to evaluate the association between Ct value at admission and patient outcome whilst adjusting carefully for covariates. Methods: We evaluated the association between Ct value at presentation and the outcomes of ICU admission and death, in patients hospitalised during the first wave of the pandemic in Southampton, UK. We adjusted for covariates including age, duration of illness and antibody sero-status, measured by neutralisation assay. Results: 185 patients were analysed, with a median [IQR] Ct value of 27.9 [22.6-32.1]. On univariate analysis the Ct value at presentation was associated with the risk of both ICU admission and death. In addition, Ct value significantly differed according to age, the duration of illness at presentation and antibody sero-status. On multivariate analysis, Ct value was independently associated with risk of death (aOR 0.84, 95% CI 0.72-0.96; p=0.011) but not ICU admission (aOR 1.04, 95% CI 0.93-1.16; p=0.507). Neutralising antibody status at presentation was not associated with mortality or ICU admission (aOR 10.62, 95% CI 0.47-889; p=0.199 and aOR 0.46, 95% CI 0.10-2.00; p=0.302, respectively). Conclusions: SARS-CoV-2 Ct value on admission to hospital was independently associated with mortality, when comprehensively adjusting for other factors and could be used for risk stratification. Trial registration: ISRCTN14966673