Diagnostic utilities of procalcitonin and C-reactive protein for the prediction of bacteremia determined by blood culture

Background: We compared the diagnostic utilities of procalcitonin (PCT) and C-reactive protein (CRP) for predicting bacteremia diagnosed by blood cultures. PCT was also evaluated as a parameter for differentiating true bacteremia from culture contamination. Methods: We analyzed a total of 3343 patients in which PCT, CRP, and blood cultures were concurrently requested for detecting bacteremia from January 2010 to December 2011. PCT concentrations were measured by the VIDAS Brahms PCT assay, and CRP concentrations were determined by a turbidimetric assay using CA-400 analyzer. Results: The PCT concentrations of bacteremia cases (n. =331) were significantly higher than those of non-bacteremia (n. =2856) (median: 3.2. ng/ml vs. 0.4. ng/ml, P<0.0001). The correlation coefficient between the PCT and CRP concentrations was 0.51. The areas under the receiver operating characteristic curves (ROC-AUCs) of PCT and CRP for discriminating bacteremia from non-bacteremia were 0.76 and 0.64, respectively. The ROC-AUC of PCT for differentiating true bacteremia from contamination was 0.86, while that of CRP was 0.65. Conclusions: PCT concentration by single testing was more useful for predicting bacteremia than CRP. PCT also exhibited diagnostic utility for ruling out blood culture contamination. Thus, PCT could be helpful in the accurate diagnosis of bacteremia.