RESULTS: The median age was 76 yr (range, 43-89 yr; IQR, 69-81), and 87.8% of the patients were male. 28 patients required exclusively non-invasive ventilation, 44 required exclusively invasive ventilation, 8 required both non-invasive and invasive ventilation, and 10 required only oxygen therapy. The median level of PCT on ICU admission was 0.30ng/mL (range, 0.02-120.00ng/mL; IQR, 0.10-1.80ng/mL), and the median APACHE II score was 19 (range, 10-43). The 28-day mortality rate was 35.6%. The 28-day survivors did show significantly decreased levels of PCT compared with non-survivors (0.25 ng/mL [range, 0.02-120.00 ng/mL] vs. 0.56ng/mL [0.05-33.44 ng/mL], Z=−2.55, P=0.01). In prediction of 28-day mortality, the area under the curve (AUC) for PCT was 0.66 (95% confidence interval [CI], 0.55-0.77) and APACHE II score was 0.68 (95% CI, 0.55-0.81). AUC was 0.68 (95%CI, 0.55-0.81) when PCT was combined with APACHE II score.