SARS-CoV-2 RNA in serum as predictor of severe outcome in COVID-19: 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, April 10 to June 30 2020 were included in a cohort. 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 positive patients. Median sampling time for initial SARS-CoV-2 in serum was 1 (IQR 1-2) day after admission corresponding to day 10 (IQR 8-12) after symptom onset. Median ages were 53 (IQR 44-67) and 63 (IQR 52-74) years for the PCR-negative and positive patients, respectively. In the serum PCR negative and positive groups 3/106 and 15/61 patients died, respectively.The hazard ratios for critical disease and all-cause mortality were 7.2 (95% CI 3.0-17) and 8.6 (95% CI 2.4-30), respectively for patients that were serum PCR positive compared to serum PCR negative.Conclusion: SARS-CoV-2 RNA in serum at hospital admission indicates a high-risk of progression to critical disease and death.