High Serum Procalcitonin: Interpret with Caution

Serum procalcitonin (PCT), which is usually produced in thyroid Ccells, is a precursor of calcitonin. In general, PCT is not released into the blood and, therefore, cannot be detected in healthy individuals [1]. However, serum procalcitonin increased significantly in response to stimulation by bacterial infections showing a favorable pharmacokinetic profile as clinical markers for bacterial infection. Consequently PCT has been used increasingly to identify systemic bacterial infections since mid of 1990 [2]. Moreover, a growing body of evidence has suggested that high serum PCT is a useful biochemical marker for discriminating between sepsis and some non-infectious causes of systemic inflammatory response syndrome and is a valuable prognostic marker [3]. A rise or no change in procalcitonin level in second week was a good predictor of outcome suggesting intensification of antibiotic therapy [2]. Recent randomized clinical trials showed that serum PCT level can be used to guide antibiotic therapy in patients with severe sepsis; it resulted in a significant reduction of antibiotic therapy and similar medical outcomes. In addition, the length of intensive care treatment in the PCT-guided group was significantly shorter than that in the control group [4,5]. In febrile neutropenia, PCT was found to be useful in diagnosing bacterial infection in these patients [6]. Noteworthy, most of the above mentioned clinical implications of PCT were derived from observational studies.