Procalcitonin (PCT) has been widely used in the diagnosis and treatment of bacterial infectious diseases in China. The investigators aim to establish an algorithm based on BRAHMS PCT (VIDAS PCT) for patients with severe infections or sepsis in the EICU to reduce antibiotic exposure and verify its validity in the reduction of antibiotic exposure, clinical outcomes and costs saving.

This is a multi-center prospective study that will establish 9 centers. Based on preliminary on-site assessments, the centers will be grouped into two arms (SOC group and PCT group) according to their capacity for daily monitoring of PCT. Each center will enroll EICU patients with severe infections or sepsis who meet the inclusion and exclusion criteria. A total of 800 patients will be enrolled, with 400 in the PCT group and 400 in the SOC group. In the PCT group, clinicians will prescribe PCT tests every day for enrolled patients, with assigning a dedicated person monitoring the daily PCT results. Once the PCT <0.5 ng/ml or ΔPCT (drop from the peak value) >80%, the clinicians will receive a notification and will strictly adhere to guidelines and PCT values to adjust antibiotic prescriptions. The SOC group will not have any intervention regarding PCT prescriptions and antibiotic adjustments. The clinicians in the SOC group will prescribe PCT at routine frequency (usually once every 2-3 days or even longer) and adjust or discontinue antibiotics according to guidelines and their experiences. The primary and secondary endpoints will be evaluated in both groups. The primary endpoint is the total duration of antibiotic use. The secondary endpoints are the length of EICU stay and the total length of hospital stay.

Inclusion Criteria:

• Age≥18
• Suspected or confirmed bacterial patients
• Stay EICU more than 3 days

Exclusion Criteria:

• age under 18 years;
• PCT concentration throughout the entire hospitalization less than 0.5 ng/ml ;
• known pregnancy; expected stay in the EICU less than 3 days;
• bone-marrow transplant or chemotherapy-induced neutropenia (<500 neutrophils per mL);
• infections for which long-term antibiotic treatment is strongly recommended (ie, infective endocarditis, osteoarticular infections, anterior mediastinitis after cardiac surgery, hepatic or cerebral abscesses, chronic prostatitis, or infection with Mycobacterium tuberculosis, Pneumocystis jirovecii, or Toxoplasma gondii);
• poor chance of survival, defined as a simplified acute physiology score (SAPS II) of more than 65 points at screening; and do-not-resuscitate orders