Severe Acute Respiratory Syndrome Coronavirus 2 RNA in Serum as Predictor of Severe Outcome in Coronavirus Disease 2019: A Retrospective Cohort Study

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). This study aimed to determine if SARS-CoV-2 RNA in serum at admission correlated with clinical outcome in COVID-19. METHODS: COVID-19 patients admitted to the infectious diseases department of a tertiary level Swedish hospital and sampled for SARS-CoV-2 RNA in serum at admission during 10 April to 30 June 2020 were included. Primary outcomes were day 28 all-cause mortality and progress to critical disease. RESULTS: The cohort (N = 167) consisted of 106 SARS-CoV-2 RNA serum-negative and 61 serum-positive patients. Median sampling time for initial SARS-CoV-2 in serum was 1 day (interquartile range [IQR], 1–2 days) after admission, corresponding to day 10 (IQR, 8–12) after symptom onset. Median age was 53 years (IQR, 44–67 years) and 63 years (IQR, 52–74 years) for the serum–negative and -positive patients, respectively. In the serum-negative and -positive groups, 3 of 106 and 15 of 61 patients died, respectively. The hazard ratios for critical disease and all-cause mortality were 7.2 (95% confidence interval [CI], 3.0–17) and 8.6 (95% CI, 2.4–30), respectively, for patients with serum–positive compared to serum–negative results. CONCLUSIONS: SARS-CoV-2 RNA in serum at hospital admission indicates a high risk of progression to critical disease and death.