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Procalcitonin-Guided Antibiotic Therapy

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Background: Procalcitonin and Its Role as a Biomarker of Bacterial Infections

Several serum biomarkers have been identified in recent years with potential uses to help diagnose local and systemic infections, differentiate bacterial and fungal infections from viral syndromes or noninfectious conditions, prognosticate, and ultimately guide management, particularly antibiotic therapy.

Currently, there are at least 178 serum biomarkers that have potential roles in managing patients with infections. Among these, procalcitonin is the most extensively studied biomarker.

Procalcitonin is the prohormone precursor of calcitonin that is expressed primarily in the C-cells of the thyroid gland and to a smaller extent in the neuroendocrine tissue of other organs, such as the lungs and intestines. The final step in the conversion of procalcitonin to calcitonin is inhibited by various cytokines and bacterial endotoxins and, therefore, high levels of cytokines and/or bacterial endotoxins cause procalcitonin levels to rise. Cytokines are released nonspecifically in response to inflammation and infection, but endotoxins are released specifically during bacterial infections because they are derived primarily from the Gram-negative bacterial cell wall. There is some evidence that procalcitonin is more specific for bacterial infections, with serum levels rising and falling more rapidly in bacterial infection.

The primary diagnostic utility of procalcitonin is thought to be in establishing the presence of local or systemic bacterial infections and in guiding their management. 

Procalcitonin is often used with algorithms to guide care in association with clinical impressions.