Procalcitonin: the bacterial and non-bacterial sepsis marker

The aim of this study was to evaluate the role of procalcitonin (PCT) in differentiating causative agents of bacterial sepsis, and sepsis from non-bacterial causes (viral, fungal, and parasitic).

This study was conducted in the Department of Microbiology (April 2023 to March 2024) and included 1,346 clinically suspected cases of bacterial, fungal, viral, and parasitic infections confirmed through various diagnostic methods. Serum/plasma samples were collected from the participants and healthy controls, and PCT levels were measured. PCT concentration of < 2 ng/mL was classified as low, while levels ≥ 2 ng/mL were considered high, serving as threshold for sepsis diagnosis.

PCT levels were significantly higher in sepsis caused by Gram-negative bacteria compared to Gram-positive bacteria, and showed a notable increase in Plasmodium infections (p < 0.0001). No significant association was observed between PCT levels and Candida albicans infections; however, cases involving non-albicans Candida species showed significantly elevated PCT levels (p = 0.0265). Infections with Cryptococcal species, hepatitis B, and hepatitis C showed a marked decrease in PCT levels. PCT levels were low in all cases involving skin commensals, with a more pronounced reduction in the case of coagulase-negative Staphylococcus compared to diphtheroids.

PCT levels showed a significant elevation in infections caused by non-bacterial agents, including Plasmodium and non-albicans Candida. A notable decline in PCT levels was observed in systemic infections caused by viruses and Cryptococcus. PCT is emerging as a universal biomarker for both bacterial and non-bacterial sepsis, making it a potential universal marker for sepsis.