Biomarkers in the intensive care setting: A focus on using procalcitonin and C-reactive protein to optimize antimicrobial duration of therapy.

Managing the critically ill patient with infection is complex, requiring clinicians to synthesize considerable information relating to antimicrobial efficacy and treatment duration. The use of biomarkers may play an important role in identifying variation in treatment response and providing information about treatment efficacy. Though a vast number of biomarkers for clinical application have been described, procalcitonin and C-reactive protein (CRP) are the most thoroughly investigated in the critically ill. However, the presence of heterogeneous populations, variable end points, and incongruent methodology in the literature complicates the use of such biomarkers to guide antimicrobial therapy. This review focuses on an appraisal of evidence for use of procalcitonin and CRP to optimize antimicrobial duration of therapy (DOT) in critically ill patients. Procalcitonin-guided antimicrobial therapy in mixed critically ill populations with varying degrees of sepsis appears to be safe and might assist in reducing antimicrobial DOT. Compared to procalcitonin, fewer studies exist examining the impact of CRP on antimicrobial DOT and clinical outcomes in the critically ill. Procalcitonin and CRP have been insufficiently studied in many key intensive care unit populations, including surgical patients with concomitant trauma, renally insufficient populations, the immunocompromised, and patients with septic shock. We believe the available evidence is not strong enough to warrant routine use of procalcitonin or CRP to guide antimicrobial DOT in critically ill patients with infection. So long as its limitations are recognized, procalcitonin could be considered to tailor antimicrobial DOT on a case-by-case basis in the critically ill patient.