Procalcitonin and other biomarkers to improve assessment and antibiotic stewardship in infections - hope for hype?

This review aims to provide physicians with an overview of the potential of procalcitonin to guide antibiotic therapy in respiratory tract infections and in sepsis. Knowledge of the strengths and weaknesses of procalcitonin are prerequisites for a rational and safe use in clinical routine. In most infections a true gold standard for diagnosis does not exist, therefore physicians must remain sceptical towards observational studies evaluating procalcitonin. Interpretation of procalcitonin levels must always include the clinical setting and knowledge of assay characteristics, particularly the setting of specific cut-off ranges and functional assay sensitivities. Highly sensitive procalcitonin measurements, embedded in a clearly defined setting and prospectively validated with clinical algorithms were repeatedly effective in markedly reducing the (over)-utilisation of antimicrobial therapy. Today, this concept has been proven for lower respiratory tract infections and in pilot studies for meningitis and critically ill patients with sepsis. The higher the absolute risk for adverse outcome of a patient, the more cautious physicians must remain and empirical antibiotic therapies must be considered despite initial low procalcitonin levels at the initial presentation. In these patients a procalcitonin-guided shortening of antibiotic courses seems appropriate. The prognostic utility of initial procalcitonin measurement in respiratory tract infections is suboptimal. Other biomarkers including cortisol, human growth hormone and prohormones from adrenomedullin and vasopressin ("copeptin") have a superior predictive potential to estimate the risk for short and long term mortality and other adverse outcomes in different diseases. An accurate prognostic assessment has the potential to optimise the management of patients and the allocation of our limited health care resources by lowering unnecessary hospitalisations and associated cost. Future intervention studies must prove if these biomarkers indeed improve clinical decision making and thus the overall medical management of patients.