Serum proteomics is a very useful tool to identify various disease. The purpose of the present study was to find differential proteins among patient with normal, SIRS, sepsis, severe sepsis, death and to screen potential biomarkers for their dynamic changes. Serum proteins were identified by iTRAQ labeling and LC-MS/MS. The bioinformatics analysis was performed with the Mascot software and the International Protein Index (IPI) and the Gene Ontology (GO) Database and KEGG pathway Database. The differentially expressed proteins were verified by Western blot by another sample collected from clinical.

Inclusion Criteria:

• Male and female aged 18 years old and over;
• clinically confirmed infection;
• fulfilled at least two criteria of systemic inflammatory response syndrome
• (a) core temperature higher than 38 °C or lower than 36 °C
• (b)respiratory rate above 20/min, or PCO2 below 32 mmHg
• (c) pulse rate above 90/min, and
• (d) white blood cell count greater than 12,000/μl or lower than < 4,000/μl or less than 10% of bands.

Exclusion Criteria:

• younger than 18 years of age;
• acquired immunodeficiency syndrome;
• reduced polymorphonuclear granulocyte counts (< 500 μL-1);
• died within 24h after admission into the ICU, or refused to participate in the study, or declined treatment during the period of observation.

All subjects were selected from among inpatients who were hospitalized between May 2010 and Mar 2012 in the Respiratory ICU, Surgical ICU, and Emergency ICU, Chinese People's Liberation Army (CPLA) General Hospital.