Usefulness of procalcitonin in differentiating Candida and bacterial blood stream infections in critically ill septic patients outside the intensive care unit

We aimed to explore the role of procalcitonin (PCT) for the diagnosis of Candida spp. bloodstream infections in a population of critically ill septic patients admitted to internal medicine units. This is a retrospective case-control study considering all cases of candidemia identified in three internal medicine units, from January 1st 2012 to May 31st 2016. For each case of candidemia, two patients with bacteremic sepsis were included in the study as control cases. The end point of the study was to evaluate the diagnostic performance of PCT for the diagnosis of Candida spp. blood stream infections in patients with objectively documented sepsis. Sixty-four patients with candidemia and 128 controls with bacteremia were enrolled. Median and interquartile range (IQR) PCT values are significantly lower in patients with candidemia (0.73; IQR 0.26-1.85 ng/mL) than in those with bacteremia (4.48; IQR 1.10-18.26 ng/mL). At ROC curve analysis, values of PCT greater than 2.5 ng/mL had a negative predictive value (NPV) of 98.3% with an AUC of 0.76 (0.68-0.84 95% CI) for the identification of Candida spp. from blood cultures. At multivariate analysis, a PCT value < 2.5 ng/mL showed an odds ratio of 8.57 (95% CI 3.09-23.70; p < 0.0001) for candidemia. In septic patients at risk of Candida infection, a PCT value lower than 2.5 ng/mL should raise the suspicion of candidemia, adding value for considering prompt initiation of antifungal therapy.