Diagnostic value of procalcitonin, interleukin-6, and interleukin-8 in critically ill patients admitted with suspected sepsis

To assess the diagnostic value of procalcitonin (PCT), interleukin (IL)-6, IL-8, and standard measurements in identifying critically ill patients with sepsis, we performed prospective measurements in 78 consecutive patients a dmitted with acute systemic inflammatory response syndrome (SIRS) and suspe cted infection. We estimated the relevance of the different parameters by u sing multivariable regression modeling, likelihood-ratio tests, and area un der the receiver operating characteristic curves (AUC). The final diagnosis was SIRS, in 18 patients, sepsis in 14, severe sepsis in 21, and septic sh ock in 25. PCT yielded the highest discriminative value, with an AUC of 0.9 2 (CI, 0.85 to 1.0), followed by IL-6 (0.75; CI, 0.63 to 0.87), and IL-8 (0 .71; CI, 0.59 to 0.83; p < 0.001). At a cutoff of 1.1 ng/ml, PCT yielded a sensitivity of 97% and a specificity of 78% to differentiate patients with SIRS from those with sepsis-related conditions. Median PCT concentrations o n admission (ng/ mi, range) were 0.6 (0 to 5.3) for SIRS; 3.5 (0.4 to 6.7) for sepsis; 6.2 (2.2 to 85) for severe sepsis; and 21.3 (1.2 to 654) for se ptic shock (p < 0.001). The addition of PCT to a model based solely on stan dard indicators improved the predictive power of detecting sepsis (likeliho od ratio test; p = 0.001) and increased the AUC value for the routine value -based model from 0.77 (CI, 0.64 to 0.89) to 0.94 (CI, 0.89 to 0.99; p = 0. 002). In contrast, no additive effect was seen for IL-6 (p = 0.56) or IL-8 (p = 0. 14). Elevated PCT concentrations appear to be a promising indicator of sepsis in newly admitted, critically ill patients capable of complement ing clinical signs and routine laboratory parameters suggestive of severe i nfection.