SARS-CoV-2 viral load as a predictor for disease severity in outpatients and hospitalised patients with COVID-19: A prospective cohort study

INTRODUCTION: We aimed to examine if severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) cycle quantification (Cq) value, as a surrogate for SARS-CoV-2 viral load, could predict hospitalisation and disease severity in adult patients with coronavirus disease 2019 (COVID-19).

METHODS: We performed a prospective cohort study of adult patients with PCR positive SARS-CoV-2 airway samples including all out-patients registered at the Department of Infectious Diseases, Odense University Hospital (OUH) March 9-March 17 2020, and all hospitalised patients at OUH March 10-April 21 2020. To identify associations between Cq-values and a) hospital admission and b) a severe outcome, logistic regression analyses were used to compute odds ratios (OR) and 95% Confidence Intervals (CI), adjusting for confounding factors (aOR).

RESULTS: We included 87 non-hospitalised and 82 hospitalised patients. The median baseline Cq-value was 25.5 (interquartile range 22.3-29.0). We found a significant association between increasing Cq-value and hospital-admission in univariate analysis (OR 1.11, 95% CI 1.04-1.19). However, this was due to an association between time from symptom onset to testing and Cq-values, and no association was found in the adjusted analysis (aOR 1.08, 95% CI 0.94-1.23). In hospitalised patients, a significant association between lower Cq-values and higher risk of severe disease was found (aOR 0.89, 95% CI 0.81-0.98), independent of timing of testing.

CONCLUSIONS: SARS-CoV-2 PCR Cq-values in outpatients correlated with time after symptom onset, but was not a predictor of hospitalisation. However, in hospitalised patients lower Cq-values were associated with higher risk of severe disease.