What is the role of procalcitonin (PCT) in diagnosing and managing intraabdominal infections?

From the Guidelines

Procalcitonin (PCT) is a valuable biomarker for diagnosing and managing intraabdominal infections, and its use can support shortening the duration of antimicrobial therapy in sepsis patients, as suggested by the Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016 1.

Key Points

• PCT levels typically rise significantly in bacterial infections, with levels above 0.5 ng/mL suggesting possible infection and levels exceeding 2.0 ng/mL strongly indicating severe bacterial infection or sepsis.
• In intraabdominal infections specifically, elevated PCT can help distinguish bacterial peritonitis from non-infectious causes of abdominal pain.
• PCT is particularly useful for monitoring treatment response, as levels typically decrease by approximately 50% every 24-36 hours with effective antimicrobial therapy.
• The most recent guidelines, such as the 2024 Clinical Practice Guideline Update by the Infectious Diseases Society of America on Complicated Intra-Abdominal Infections, emphasize the importance of risk assessment, diagnostic imaging, and microbiological evaluation in adults, children, and pregnant people 1.

Limitations and Considerations

• PCT has limitations—it may be elevated in non-infectious conditions like trauma or surgery, and certain infections (particularly localized, fungal, or viral) may not trigger significant PCT elevation.
• For optimal use in clinical practice, PCT should be measured at diagnosis and serially during treatment, with results interpreted alongside clinical findings, imaging studies, and other laboratory markers.

Clinical Application

• The use of PCT can guide antibiotic duration decisions, potentially allowing for shorter courses when levels normalize rapidly, as supported by the Surviving Sepsis Campaign guidelines 1.
• Clinicians should consider the patient's overall clinical condition, the severity of the infection, and the presence of any underlying conditions that may affect PCT levels when interpreting results.
• The World Society of Emergency Surgery (WSES) 2016 consensus conference recommendations also highlight the importance of a comprehensive approach to managing intraabdominal infections, including source control, antibiotic therapy, and supportive care 1.

From the Research

Role of Procalcitonin in Diagnosing Intraabdominal Infections

• Procalcitonin (PCT) is a biomarker that has been studied for its potential role in diagnosing and managing intraabdominal infections 2.
• PCT has been shown to be elevated in bacterial infections, but not in viral infections or other inflammatory conditions, making it a useful marker for differentiating between bacterial and non-bacterial infections 3.
• The use of PCT-guided therapy has been shown to reduce antibiotic use and improve patient outcomes in various clinical settings, including respiratory infections and sepsis 4, 5.

Procalcitonin-Guided Antibiotic Therapy

• Studies have demonstrated that PCT can be used to guide antibiotic therapy, with a cutoff value of 0.25 μg/L in non-ICU patients or 0.5 μg/L in ICU patients being used to make decisions about initiation and discontinuation of antibiotic therapy 3.
• A subsequent drop of >80% in PCT levels appears to be reasonable for discontinuing antibiotics in patients with a significantly elevated baseline PCT level 3.
• PCT-guided antibiotic stewardship has been shown to reduce antibiotic exposure and associated side-effects among patients with respiratory infection and sepsis 6.

Clinical Use of Procalcitonin

• PCT should not be viewed as a traditional diagnostic marker, but rather as a tool to help differentiate bacterial from non-bacterial infections and inflammation states 6.
• The use of PCT in clinical routine should be based on validated diagnostic algorithms and careful patient assessment, taking into account factors such as pretest probability for bacterial infection, acuity and severity of presentation, and PCT test results 6.
• Low PCT levels can help rule out bacterial infection in patients with low pretest probability for bacterial infection and low-risk general condition, while high PCT levels can guide decisions regarding empiric antibiotic treatment and subsequent monitoring of PCT to track the resolution of infection 6.