Serum procalcitonin levels distinguish Gram-negative bacterial sepsis from Gram-positive bacterial and fungal sepsis

Abstract

Background: Serum procalcitonin (PCT) levels differ in patients with bacterial or fungal infections and are significantly elevated in patients with Gram-negative bacteremia. We evaluated the diagnostic accuracy of different inflammatory markers to discriminate sepsis caused by different pathogens.

Materials and methods: We included 328 episodes of bacteremia from 292 patients with sepsis and 31 patients with suspected sepsis in this study. Medical records of patients who had bacteremia caused by Gram-negative bacteria (Gram-negative), Gram-positive bacteria (Gram-positive) or fungi were reviewed, and information about PCT and other inflammatory markers was recorded. The diagnostic performance of inflammatory markers was calculated via receiver operating characteristic (ROC) curves.

Results: Serum PCT levels in Gram-negative, Gram-positive, and fungal sepsis were 7.47 (interquartile range [IQR]: 1.09-41.26) ng/mL, 0.48 (IQR: 0.15-2.16) ng/mL, and 0.60 (IQR: 0.14-2.06) ng/mL, respectively (P < 0.001). ROC analysis revealed an optimal cut-off value of 2.44 ng/mL for PCT in discriminating Gram-negative sepsis from Gram-positive sepsis, which yielded a sensitivity of 68.4% and a specificity of 77.1%. An optimal cut-off value of 3.11 ng/mL for PCT in discriminating Gram-negative sepsis from fungal sepsis, led to a sensitivity of 63.9% and specificity of 93.3%. Neither PCT nor other inflammatory markers could be used to distinguish between Gram-positive and fungal sepsis.

Conclusion: Serum PCT levels were significantly higher in patients with Gram-negative sepsis than in those with Gram-positive or fungal sepsis. PCT is a potential sensitive biomarker for distinguishing Gram-negative sepsis from Gram-positive and fungal sepsis.

Keywords: Fungi; Gram-negative bacteria; procalcitonin; sepsis.

Figure 1

(a and b) Serum procalcitonin and C-reactive protein levels in patients with Gram-positive bacterial sepsis, Gram-negative bacterial sepsis, fungal sepsis and suspected sepsis. (c) Serum procalcitonin levels in patients with sepsis caused by Escherichia coli, Klebsiella pneumoniae, or other bacteria. Data are presented as a box plot with median lines 25^th and 75^th percentile boxes, and 10^th and 90^th percentile error bars. The Y-axis is a log two scale in (a and c). NS: Not statistically significant, *P < 0.05. (d) Receiver operating characteristic curve for procalcitonin levels to distinguish Gram-negative sepsis from Gram-positive sepsis