The aim of the study was to analyze the ratio of serum PCT in ICU patients with bacterial pneumonia to SDI values obtained by the metagenomic next-generation sequencing technique (mNGS), and then compared with SDI, PCT, C-reactive protein (CRP), and CRP/SDI to evaluate the value of PCT/SDI in the short-term prognosis of ICU patients with SBP. Here, CRP is linked to bacterial pneumonia.