Biomarkers in pulmonary infections: a clinical approach

Abstract

Severe acute respiratory infections, such as community-acquired pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia, constitute frequent and lethal pulmonary infections in the intensive care unit (ICU). Despite optimal management with early appropriate empiric antimicrobial therapy and adequate supportive care, mortality remains high, in part attributable to the aging, growing number of comorbidities, and rising rates of multidrug resistance pathogens. Biomarkers have the potential to offer additional information that may further improve the management and outcome of pulmonary infections. Available pathogen-specific biomarkers, for example, Streptococcus pneumoniae urinary antigen test and galactomannan, can be helpful in the microbiologic diagnosis of pulmonary infection in ICU patients, improving the timing and appropriateness of empiric antimicrobial therapy since these tests have a short turnaround time in comparison to classic microbiology. On the other hand, host-response biomarkers, for example, C-reactive protein and procalcitonin, used in conjunction with the clinical data, may be useful in the diagnosis and prediction of pulmonary infections, monitoring the response to treatment, and guiding duration of antimicrobial therapy. The assessment of serial measurements overtime, kinetics of biomarkers, is more informative than a single value. The appropriate utilization of accurate pathogen-specific and host-response biomarkers may benefit clinical decision-making at the bedside and optimize antimicrobial stewardship.

Keywords: C-reactive protein; Host-response biomarkers; Pathogen-specific biomarkers; Procalcitonin; Pulmonary infections.

Fig. 1

Clinician’s guide to use pathogen-specific and host-response in severe respiratory infection. 1. Refer to the text for details on accuracy of biomarkers, specifics of their indication and limitations; 2. Dashed line indicates experimental biomarkers, not yet incorporated into clinical practice; 3. Bacterial and fungal (especially Aspergillus) pulmonary infection can occur as a complication of primary viral infection (e.g., Influenza, COVID-19); $The antibiotic therapy must be started within 1 h in patients with sepsis and, particulary, in those with septic shock. De-scalation of antibiotics should be made whenever possible after 2–3 days of therapy, based on initial laboratory test results and clinical information."; & These etiologies are more common among imunnocompromised patients (HIV, transplant, use of immunosupressant drugs, among others); #Specially in invasively ventilated patients. NAAT nucleic acid amplification test; CSF cerebrospinal fluid, CRP C-reatvie protein, PCT procalcitonin