Procalcitonin May be a Better Predictor of Interleukin-6 than Conventional Inflammatory Markers

Objective: To determine the correlation and predictive accuracy of conventional inflammatory variables (body temperature, leukocyte count, neutrophil percentage, absolute neutrophil count [ANC], C-reactive protein [CRP]) and a new inflammatory marker, procalcitonin (PCT), with elevated levels of interleukin-6 (IL-6) in septic patients. Materials and Methods: Fifty-one patients were enrolled in the study. Systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, and septic shock were diagnosed according to ACCP/SCCM criteria. Serum concentrations of PCT, IL-6 and CRP were determined within 24 hours after the clinical onset of sepsis or SIRS. Leukocyte count, neutrophil percentage, and ANC, as well as maximal body temperature were also recorded. Results: Among all investigated variables, PCT most significantly correlated with serum IL-6 levels. Based on area under the receiver operating characteristics curve, PCT exhibited the highest predictive capability (0.685 for IL-6 ¡Ý 500 pg/mL, and 0.858 for IL-6 ¡Ý 1000 pg/mL), body temperature (0.662 and 0.792, respectively) and CRP (0.625 and 0.727, respectively) offered moderate predictive accuracy, while leukocyte count, neutrophil percentage and ANC carried the lowest predictive capability. Sensitivity, specificity, positive and negative predictive values all followed the same pattern. Conclusion: Compared with conventional inflammatory variables, PCT may reflect more reliably the elevated IL-6 levels.