Diagnostic value of procalcitonin serum levels in neutropenic patients with fever: comparison with interleukin-8.

We assessed the predictive value of procalcitonin (PCT) serum levels in neutropenic patients with fever and various types of infection, using a prospective 3 times weekly blood sampling protocol during 103 patient episodes. Compared with pre-fever levels, median PCT levels increased after fever onset from 0.16 ng/ml (day -1) to 0.34 ng/ml (day +1). In samples obtained within 32 h after fever onset, PCT levels differed significantly between (clinically or microbiologically) documented infection and unexplained fever (median 0.51 vs. 0.26 ng/ml), between bacteraemia and non-bacteraemic infection (median 0.8 vs. 0.27 ng/ml) and between Gram-negative bacteraemia and all other episodes (median 1.28 vs. 0.31 ng/ml). Receiver-operating-characteristic (ROC) curves indicated that the discriminatory power of PCT was best for predicting bacteraemia vs. non-bacteraemic infection (sensitivity 73%; specificity 86%; area under the ROC curve 0.795; cut-off value 0.5 ng/ml). Compared with interleukin-8 (IL-8) serum levels, test characteristics were similar in the prediction of bacteraemia vs. non-bacteraemic infection and in the prediction of documented infection vs. unexplained fever, while IL-8 was better than PCT in the prediction of Gram-negative bacteraemia (area under the ROC curve 0.965 vs. 0.758).