Antibiotic resistance is driven by overuse, especially for viral respiratory infections. Procalcitonin (PCT), a biomarker for bacterial infections, helps guide antibiotic therapy more precisely, reducing unnecessary use and improving outcomes. Studies, including large trials and economic models across several countries, show PCT-guided treatment lowers mortality, antibiotic exposure, therapy duration and related complications, potentially reducing hospital costs despite initial testing expenses.

Antibiotic resistance (ABR) poses a significant threat to global health and is largely driven by the overuse of antibiotics, particularly for acute respiratory tract infections (ARTIs), which are mostly viral. Despite this, antibiotics are frequently prescribed, often for unnecessarily long durations due to the lack of reliable markers indicating illness resolution. This has led to an interest in using biomarkers like procalcitonin (PCT) to guide antibiotic therapy more accurately.

PCT is a precursor of the hormone calcitonin and increases significantly in the presence of bacterial infections, offering a promising tool for distinguishing bacterial from viral infections and for monitoring infection progression and response to treatment. It rises within hours of infection onset, peaks by day two, and decreases with recovery, making it useful for deciding when to start or stop antibiotics.

Clinical studies, including the large PRORATA randomized controlled trial, have demonstrated that PCT-guided antibiotic protocols are safe and effective in reducing antibiotic use without compromising patient outcomes. A Cochrane review further supported this, showing that PCT-guided therapy reduces mortality, antibiotic consumption, and antibiotic-related adverse effects in patients with ARTIs.

However, PCT testing has yet to be widely adopted in hospitals due to concerns about its cost-effectiveness and implementation challenges. To address these concerns, a series of health economic evaluations have been carried out: they assess the clinical and economic impact of PCT-guided therapy, particularly its role in reducing complications such as ABR and Clostridium difficile infections (CDI).

Findings consistently show that PCT-guided antibiotic therapy not only improves patient outcomes but also reduces direct healthcare costs when compared to standard care. Recent modeling incorporating RWE from a U.S. hospital further confirmed these benefits in real-world settings, strengthening the case for broader adoption of PCT in hospital-based antibiotic stewardship programs.

Inclusion Criteria:

• age ≥18 years;
• clinical and instrumental diagnosis of LRTI consistent with bacterial origin and requiring antimicrobial treatment;
• patient hospitalized in Internal Medicine, Geriatrics, Infectious Disease unit, Pneumology, Semi Intensive Care unit, ICU, Emergency Medicine;
• informed consent provided by the patient.

Exclusion Criteria:

• age < 18 years;
• lack of informed consent;
• severe immunosuppression (other than related to corticosteroid use);
• concomitant diagnosis of other infections requiring long term antimicrobial therapy (i.e. endocarditis, osteomyelitis)