The role of procalcitonin in reducing antibiotics across the surgical pathway
Executive Summary
Procalcitonin (PCT) has emerged as a critical, highly sensitive biomarker for bacterial infection, providing general and emergency surgeons with an objective tool to optimize antibiotic (AB) therapy and surgical decision-making. Historically, up to 30–50% of antibiotics administered to hospitalized patients have been unnecessary, contributing to antimicrobial resistance, adverse drug events, and the spread of Clostridioides difficile.
This briefing document synthesizes recommendations from a multidisciplinary task force regarding the application of PCT across various surgical pathways. Key findings indicate that PCT-guided protocols can significantly reduce the duration of antibiotic exposure in secondary peritonitis, differentiate between complicated and uncomplicated diverticulitis, identify early-phase infections in acute pancreatitis where traditional markers (CRP and WBC) fail, and assist in the early diagnosis of post-traumatic sepsis. Furthermore, PCT levels serve as reliable indicators for the safe discharge of patients following colorectal resections and guide the aggressive management of necrotizing soft tissue infections.
Technical Overview of Procalcitonin (PCT)
PCT is a 116 amino acid polypeptide prohormone of calcitonin. While primarily synthesized by the thyroid gland's C cells, its production can be stimulated in nearly every organ by inflammatory cytokines and bacterial endotoxins.
Sensitivity: High levels of PCT in the blood correlate directly with the likelihood of systemic infection and sepsis.
Clinical Utility: Unlike other biomarkers, PCT provides objective data that allows clinicians to decisively start, withhold, or terminate antibiotic courses.
Clinical Applications in Surgical Pathways
1. Secondary Peritonitis and Relaparotomy
In patients undergoing surgery for secondary peritonitis, PCT values and trends are essential for determining the duration of treatment and the necessity of further surgical intervention.
Antibiotic Stewardship: Research demonstrates that PCT-guided algorithms can reduce antibiotic exposure by approximately 50%. In one prospective study, the median duration of treatment was reduced from 6.1 days to 3.4 days without compromising patient outcomes.
Relaparotomy Decisions: Selecting patients for "on-demand" relaparotomy (performed only upon clinical deterioration) is traditionally subjective. PCT serves as a valuable laboratory variable to identify persistent infection.
Focus Index (FI): A PCT ratio calculated on postoperative days 1 and 2.
Cutoff Value: An FI > 1.1 indicates effective treatment, while values < 1.1 suggest poor control of the infectious focus (93% sensitivity).
2. Acute Diverticulitis
PCT is instrumental in differentiating between uncomplicated and complicated diverticulitis (Hinchey > Ib), which is crucial for avoiding unnecessary antibiotic use.
Diagnostic Precision: In a prospective cohort study, the median PCT for uncomplicated cases (0.05 ng/L) was significantly lower than for complicated cases (0.13 ng/L).
Thresholds: Using a cutoff value of 0.1 ng/L (highest value on days 1 and 2) yielded a sensitivity of 81% and specificity of 91% for identifying complicated cases.
Superiority: Unlike C-reactive protein (CRP) and leucocyte counts, PCT accurately identifies cases that truly benefit from antibiotics.
3. Acute Pancreatitis (AP)
Despite guidelines, there is a global overuse of prophylactic antibiotics in AP, with reports suggesting up to 77.1% of patients receive therapy without signs of infection.
Early Phase Biomarker: PCT is the only marker associated with infection in the early phase of AP. Traditional markers like CRP, WBC, lipase, and amylase are ineffective during this window.
Guideline Recommendations:
Statement: CRP and WBC should not be used for decision-making regarding antibiotics in the early phase.
Statement: Progressive elevation of CRP is a normal inflammatory response in AP and should not trigger antibiotic treatment.
Statement: Elevated PCT during the early phase is associated with infection and can justify starting antibiotics even in the absence of proven infection.
4. Trauma Care
Identifying infection in trauma patients is challenging because surgery, massive transfusions, and SIRS can influence biomarker levels.
Early vs. Late Trends: PCT values in the first 48 hours may reflect the impact of the trauma itself. However, a long-lasting elevation or a repeated increase is a strong indicator of developing septic complications.
Predictive Power: PCT has been found to be the only significant predictor for sepsis in critically ill trauma patients (odds ratio 2.37).
Spinal Cord Injury: In patients with acute traumatic spinal cord injury, a PCT cutoff of 0.1 ng/L can exclude infection with 92% sensitivity, allowing antibiotics to be withheld.
5. Colorectal Resection and Anastomotic Leaks
Anastomotic leakage (AL) is a severe complication with an incidence of 3–10%.
Preclinical Diagnosis: PCT levels following colorectal cancer resection can identify patients at low risk for AL.
ERAS Protocols: This marker is a "game changer" for Enhanced Recovery After Surgery (ERAS) protocols, providing a reliable laboratory indicator to support safe early discharge and reduce healthcare costs.
6. Acute Bacterial Skin and Skin Structure Infections (ABSSSI)
In critical cases like necrotizing soft tissue infections (NSTIs), where mortality rates range from 10–30%, PCT plays a pivotal role.
Care Pathway Stages: PCT is used for diagnostic staging, monitoring therapeutic response to debridement, de-escalation of therapy, and determining when to stop antibiotics.
Surgical Reevaluation: The PCT ratio (Day 1 vs. Day 2) is a highly sensitive tool for evaluating the success of surgical source control and necrosectomy.
Summary of Diagnostic Cutoffs and Indicators
Conclusion
The expert panel concludes that PCT is a highly sensitive biomarker that offers acute care surgeons an objective means to navigate the "therapeutic mantra" of surgical infections. By integrating PCT trends with clinical evaluation, surgeons can reduce the selection pressure on resistant pathogens, minimize drug toxicity, and improve the overall quality of care across the surgical pathway.
