Thomas-Ruddel DO, et al. - In this secondary analysis of the prospectively collected patient-level dataset from a cluster randomized quality improvement trial including sepsis patients with organ dysfunction treated in the participating intensive care units from 2011 to 2015, researchers assessed the accuracy of procalcitonin (PCT) serum concentrations to diagnose Gram-negative bacteremia as well as the association of PCT serum concentrations with more specific pathogens and the focus of infection. The observed higher serum PCT concentrations in patients with Gram-negative bacteremia vs in patients with Gram-positive bacteremia or candidemia had no utility in guiding therapeutic decisions due to too low discriminatory power of this difference. Gram-negative or Gram-positive bacteria were not the only determinants of variations in PCT serum concentrations. These were also influenced by distinct groups of pathogens and different foci of infection.