Patients classification
Patients were classified into asymptomatic, presymptomatic, and
symptomatic groups based on the retrospective review of the medical
records. Asymptomatic COVID-19 patients were those with SARS-CoV-2
nucleic acid test positive but without any clinical symptom or only with
stable pre-exist chronic symptoms (e.g., chronic cough without
worsening). Presymptomatic patients were those asymptomatic inpatients
on admission but then developed typical (fever, cough, shortness of
breath) or atypical symptom (14, 15). Symptomatic patients were those
who had typical clinical symptoms on admission.
The diagnosis and severity degree of each patient was determined
according to the clinical classification criterion in Diagnosis and
Treatment Protocol for Novel Coronavirus Pneumonia released by the
National Health Commission (6th or 7th edition). In clinical, patients
were classified into mild or moderate, severe, and critical cases,
depending on the above criterion. In our analysis, the clinically
defined severe or critical COVID-19 patients were grouped into severe
cases group, and the clinically defined mild or moderate COVID-19
patients were defined as non-severe group cases.