Serum procalcitonin is used as a marker for sepsis and can guide decisions regarding:

• A. Antibiotic duration
• B. Nutritional support
• C. Oxygen therapy
• D. Vaccination timing

Answer: (A)

Procalcitonin rises in bacterial infections and sepsis, so it’s used to tailor antibiotic treatment rather than other aspects of care. When PCT levels are elevated, antibiotics are started or continued; as the infection resolves, serial measurements typically fall, providing a signal that it may be safe to stop antibiotics earlier or avoid prolonged courses. This is why it’s a tool for guiding how long antibiotics should be given.

Nutritional support, oxygen therapy, and vaccination timing are guided by different inputs—nutritional status and energy needs, respiratory assessment and support requirements, and immunization schedules—rather than PCT levels, so procalcitonin is not used to determine those decisions.

Keep in mind that procalcitonin is not perfect; factors like recent surgery, trauma, or kidney dysfunction can affect levels, so decisions should always factor in the overall clinical picture.