Comparison of Diagnostic Utility between Procalcitonin and C-Reactive Protein for the Patients with Blood Culture-Positive Sepsis

Background : Procalcitonin (PCT) is a relatively new marker for bacterial infections, and its diagnostic utility has been variable across the studies. We investigated the diagnostic utility of PCT for the patients with blood culture-positive sepsis, and compared it with that of C-reactive protein (CRP). Methods : In 1,270 consecutive blood samples, PCT and CRP were simultaneously measured and results were compared according to the five categories of PCT concentrations (<0.05 ng/mL; 0.05-0.49 ng/mL; 0.5-1.99 ng/mL; 2-9.99 ng/mL; >= 10 ng/mL). In 506 samples, they were further analyzed according to the result of blood culture. PCT and CRP were measured using enzyme-linked fluorescent assay (bioMerieux Co., France) and rate nephelometry (Beckman Coulter Co., USA), respectively. Their diagnostic utilities were compared using ROC curves. Results : The mean concentrations of CRP in five categories of PCT were 15.4 mg/L, 42.1 mg/L, 101.2 mg/L, 125.0 mg/L, 167.1 mg/L, respectively (P<0.0001). Both PCT and CRP showed significant differences between the two positive and negative groups of blood culture (PCT, 8.47 vs 2.44 ng/mL, P=0.0133; CRP, 110.48 vs 59.78 mg/L, P<0.0001). The areas under the ROC curves (95% confidence interval) for PCT and CRP were 0.720 (0.644-0.788) and 0.558 (0.478-0.636), respectively, and showed a significant difference (P=0.005). Conclusions: The diagnostic utility of PCT is superior to that of CRP for the patients with blood culture-positive sepsis. PCT seems to be reliable for sepsis diagnosis, and may provide useful information for the critically ill patients. (Korean J Lab Med 2009;29:529-35)