Sepsis biomarkers and pathogen detection methods: State of the art

Evidence-based blood culture testing is of utmost importance for ICU patients with suspected sepsis or organ infection. Knowledge of the etiologic agent (bacteria or fungi) and their susceptibility against antimicrobials enables the clinician to initiate an appropriate antimicrobial therapy and guides diagnostic procedures. This has been shown to reduce mortality, ICU-stay and antibiotic overuse. Whereas microbiological laboratory practice has been highly standardized, short­falls in the preanalytic procedures in the ICU (indication, timing, volume, numbers, collection of blood cultures) have a significant effect on the diagnostic yield. Due to system-related drawbacks of molecular diagnostics, i.e. PCR-based pathogen detection, which are arguable sensitivities, the failing of the 'fast time-to-result argument', no solution to establish a comprising antibiogram, still ongoing discussions on the coverage of the tar­get panel, high overall costs, and the lacking of resilient data on clinical utility, non-culture-based NATs do currently not represent an alternative to blood culture testing. Inflammatory markers are recognized to play an increasingly important role in the diagnosis and monitoring of sepsis. This is partly due to low specificity of clinical symptoms and conventional inflammatory signs for the diagnosis of sepsis but also to a lack of correlation with the severity of the inflammatory response. Elevated serum PCT levels indicate systemic inflammation reliably. PCT is the only sepsis marker that is helpful in the differentiation between infectious and non-infectious causes of organ dysfunction and shock and might support antibiotic therapy.