Serum procalcitonin and interleukin-6 levels may help to differentiate systemic inflammatory response of infectious and non-infectious origin.

OBJECTIVE: To evaluate the efficacy of using procalcitonin (PCT) and interleukin-6 (IL-6) to differentiate sepsis from non-infectious systemic inflammatory response syndrome (SIRS).
METHODS: We made a prospective study in a general intensive care unit at Peking Union Medical College Hospital. Twenty patients with sepsis and 31 patients with non-infectious SIRS were enrolled in this study. Serum concentrations of PCT, IL-6 and C-reactive protein (CRP) were determined within 24 h after clinical onset of sepsis or non-infectious SIRS. Leukocyte count, percentage of neutrophils, and absolute neutrophil count, as well as maximal body temperature were also recorded.
RESULTS: Serum concentrations of PCT, IL-6, and CRP, as well as maximal body temperature, were significantly higher in septic patients [3.6 (1.8, 27.5) micro g/L, 810 +/- 516 ng/L, 180 +/- 108 g/L, 38.6 +/- 1.2 degrees C] than non-infectious SIRS patients [0.5 (0.2, 1.8) micro g/L, 235 +/- 177 ng/L, 109 +/- 70 g/L, 37.9 +/- 0.9 degrees C]. IL-6 and PCT exhibited the best discriminative power between sepsis and non-infectious SIRS, with sensitivity above 80% and specificity above 70%. A sepsis score with combination of IL-6 and PCT showed the best discriminative power with the area under the receiver operating characteristic curve of 0.923.
CONCLUSIONS: Assessing IL-6 and PCT levels are more reliable ways to differentiate sepsis from non-infectious SIRS, compared with conventional inflammatory parameters.