In a hospitalised adult admitted with community-acquired pneumonia, serial procalcitonin measurements are used to guide antibiotic therapy. What is the principal rationale?
- A Low and falling procalcitonin supports early discontinuation of antibiotics in patients unlikely to have bacterial infection ✓
- B Procalcitonin identifies the specific bacterial species causing pneumonia
- C Procalcitonin replaces chest radiography for confirming resolution
- D Procalcitonin distinguishes viral from fungal pneumonia specifically
Correct answer: A. Low and falling procalcitonin supports early discontinuation of antibiotics in patients unlikely to have bacterial infection
Explanation
Procalcitonin rises substantially in systemic bacterial infection and stays low in most viral illnesses. Protocols use a value below about 0.1 µg/L to discourage initiation and a fall below 0.25 µg/L to support stopping antibiotics, reducing exposure without worsening outcomes. It carries no species-level information, so it never guides targeted therapy, which kills option B. Chest radiography remains the tool for assessing radiological response, and procalcitonin cannot reliably separate viral from fungal disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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