Clinical Utility of Procalcitonin and Its Association With Pathogen Types and Prognosis in Patients With Bloodstream Infection

BACKGROUND: Procalcitonin (PCT) levels have been reported less frequently in polymicrobial bloodstream infection (BSI). The purpose of this study is to assess the value of serum PCT in early identifying pathogen types isolated from BSI including mixed microorganisms and predicting patient outcomes. METHODS: Between January 2012 and December 2018, medical records were collected on adult patients with BSI who met the inclusion criteria and underwent PCT testing within 24 h of the onset. RESULTS: 817 episodes were included in the study. The 30-day mortality rate among patients with polymicrobial BSI was notably elevated compared to those with monomicrobial BSI (50.0% vs. 16.9%, p < 0.001). A notable increase in PCT levels was detected in non-survivors when compared to survivors (6.06 ng/mL vs. 1.23 ng/mL, p < 0.001). Receiver operating characteristic curve (ROC) analysis showed that a PCT level of 3.79 ng/mL yielded a 49.4% sensitivity, a 77.6% specificity, an 83.0% positive predictive value (PPV) and a 40.9% negative predictive value (NPV) for gram-negative or multiple bacteria BSI (the area under the curve 0.642, p = 0.0199). Additionally, the areas under the ROC curve of PCT predicting 30-day mortality was 0.674 (p = 0.0238) with a cut-off value of 1.11 ng/mL, a sensitivity of 79.9%, a specificity of 49.0%, a PPV of 25.9% and a NPV of 91.6%. CONCLUSIONS: The significant elevation of PCT levels may contribute to early distinguishing gram-negative or polymicrobial BSIs and outcome evaluation with low-to-moderate discriminatory ability, thus optimizing antibiotic treatment regimens and improving the prognosis.