Receiver operating characteristic (ROC) curve of serum procalcitonin (PCT) for the diagnosis of blood stream infection in critically ill patients with either primary (
. A), or secondary (
. B) sepsis. Plain circles indicate PCT values. Area under the ROC curve = 0.934, 95% CI: 0.881–0.970; vs. 0.805, 95% CI: 0.699–0.879, respectively; p < 0.050.