Definition
Fever was defined as an axillary temperature of 37.3°C or higher.
Hypoxemia
was defined as PaO2/FiO2 < 300
mmHg [18]. Acute respiratory distress syndrome (ARDS) was diagnosed
according to ARDS Berlin definition, i.e. severe hypoxemia
(PaO2/FiO2≤ 300 mmHg with PEEP ≥ 5 cmH2O), associated with bilateral opacities on
chest X-ray, which could not be fully explained by cardiac failure or
fluid overload [29]. Obesity was considered if patients with a body
mass index of more than 28 kg/m2. Pneumonia severity
was assessed by CURB-65 [30] and the Pneumonia Severity Index (PSI)
[31]. Severe pneumonia was according to modified ATS criteria
[23]. Viral and bacterial/fungal superinfection was defined as the
detection of both viruses and bacteria/fungi [13, 18]. Mixed viral
infection was defined as concurrent detection of both virus detection of
≥
2 viruses. Leukocytosis: leukocyte count >
10,000/mm3. Neutrophilopenia: neutrophilic granulocyte
count < 1500/mm3. Lymphocytopenia:
lymphocyte count < 1000/mm3. Anemia:
hemoglobin <120 g/L for men and <110 g/L for women.
Thrombocytopenia: platelet count <
150,000/mm3.