The Effect of Repeated Versus Initial Procalcitonin Measurements on Diagnosis of Infection in the Intensive Care Setting: A Prospective Observational Study

Host Diagnostic Biomarkers of Infection in the ICU: Where Are We and Where Are We Going?

Purpose of Review

Early identification of infection in the critically ill patient and initiation of appropriate treatment is key to reducing morbidity and mortality. On the other hand, the indiscriminate use of antimicrobials leads to harms, many of which may be exaggerated in the critically ill population. The current method of diagnosing infection in the intensive care unit relies heavily on clinical gestalt; however, this approach is plagued by biases. Therefore, a reliable, independent biomarker holds promise in the accurate determination of infection. We discuss currently used host biomarkers used in the intensive care unit and review new and emerging approaches to biomarker discovery.

Recent Findings

White cell count (including total white cell count, left shift, and the neutrophil-leucocyte ratio), C-reactive protein, and procalcitonin are the most common host diagnostic biomarkers for sepsis used in current clinical practice. However, their utility in the initial diagnosis of infection, and their role in the subsequent decision to commence treatment, remains limited. Novel approaches to biomarker discovery that are currently being investigated include combination biomarkers, host 'sepsis signatures' based on differential gene expression, site-specific biomarkers, biomechanical assays, and incorporation of new and pre-existing host biomarkers into machine learning algorithms.

Summary

To date, no single reliable independent biomarker of infection exists. Whilst new approaches to biomarker discovery hold promise, their clinical utility may be limited if previous mistakes that have afflicted sepsis biomarker research continue to be repeated.

Rapid and Point-of-Care Testing in Respiratory Tract Infections: An Antibiotic Guardian?

This is a narrative review on the potential of rapid and point-of-care microbiological testing in pneumonia patients, focusing particularly on hospital-acquired and ventilator-associated pneumonia, which have substantial mortality and diverse microbiology. This work is written from a United Kingdom perspective, but much of it is generalizable internationally. In a world where antimicrobial resistance is a major international threat, the use of rapid molecular diagnostics has great potential to improve both the management of pneumonia patients and the stewardship of antibiotics. Rapid tests potentially can distinguish patients with bacterial versus viral infection and can swiftly identify bacterial pathogens and their resistances. We seek to answer the question: “Can such tests be used as an antibiotic guardian?” Their availability at the bedside rather than in the laboratory should best ensure that results are swiftly used to optimize patient management but will raise new challenges, not the least with respect to maintaining quality control and microbiology/infection control input. A further challenge lies in assessing the degree of trust that treating clinicians will place in these molecular diagnostic tests, particularly when early de-escalation of antibiotic therapy is indicated.