OBJECTIVE:Sepsis is still major cause of morbidity and mortality, despite improvements in diagnosis and treatment in modern medicine. Therefore, laboratory examinations that provide correct and rapid results are needed to support the diagnosis. This study was conducted to investigate value of immunological indicators procalcitonin (PCT) and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in differential diagnosis of patients with sepsis and systemic inflammatory response syndrome (SIRS), as well as to assess their importance in determining prognosis of patients with sepsis.METHODS:Total of 90 patients, 38 with SIRS and 52 with sepsis, who were between the ages 20 to 92, were included in this prospectively planned study. Blood sample was collected from the patients during hospitalization and again in follow-up visit. Enzyme-linked immunosorbent assay (MyBioSource, Inc., San Diego, CA, USA) was used to measure sTREM-1, and PCT was measured using mini VIDAS B.R.A.H.M.S PCT assay (Biomerieux, S.A., Marcy-l’Étoile, France). In addition, patients were clinically assessed using Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system.RESULTS:On day of intensive care unit admission, sTREM-1 and PCT levels, as well as APACHE II score were significantly higher in sepsis group than SIRS group (p=0.001, p=0.01, p=0.001, respectively). Values of sTREM-1 and APACHE II score were higher in the patients with positive blood cultures than those with negative culture results (p=0.002, p=0.006, respectively). PCT, C-reactive protein, and sTREM-1 levels were significantly higher in nonsurviving group. In differentiation of SIRS from sepsis, sTREM-1 cut-off value ≥133 pg/mL and PCT cut-off value of 1.57 ng/mL yielded sensitivity of 71.1% and 67.33%, and specificity of 73.3% and 65.79%, respectively.CONCLUSION:In patients with suspected sepsis, sTREM-1 and PCT can be used as indicators, in addition to scoring systems such as APACHE II and Sepsis-related Organ Failure Assessment score. However, it would be appropriate to support present findings with studies of larger series.