Procalcitonin

Procalcitonin (PCT) is a protein containing 116 amino acids and is accepted as the prohormone of calcitonin synthesized in the thyroid gland [1]. Although plasma calcitonin has been shown not to change signifi cantly in serious bacterial infections, PCT plasma concentrations have been found to be high [1,2]. PCT is produced ubiquitously in response to endotoxin or mediators released in response to bacterial infections (i.e. interleukin 1 beta (IL-1 β ), tumour necrosis factor alpha (TNFα ), and IL-6) and strongly correlates with the extent and severity of bacterial infections [3]. Sepsis is reported to be the most common cause of death in the non-coronary intensive care unit (ICU). Approximately 25 – 35% of patients with severe sepsis and 40 – 55% of patients with septic shock die within 30 days [4]. Early diagnosis of septic complications followed by early and adequate antibiotic therapy may improve the survival rate of critically ill patients [5]. Several studies have shown the usefulness of PCT in differentiating bacterial infections from other causes of infl ammatory or septic reactions. Serial measurements of PCT have been most useful [6]. PCT has been compared to several other markers of sepsis, especially C-reactive protein (CRP), the most commonly used and sensitive marker of infl ammation. PCT has been shown to be more specifi c and to have a higher positive predictive value than CRP. Thus the clinical value of PCT appears to be promising [7]. A growing body of evidence supports the use of PCT to improve the diagnosis of bacterial infections and to guide antibiotic therapy [8]. We performed a study of 50 patients in our intensive care unit; PCT measurements were done on the day of diagnosis of sepsis and the following days. In this study we found that PCT levels on day 0 and on day 4 were meaningfully related to the prognosis [9]. This is in agreement with the study of Lavrentieva et al., who emphasized that the PCT level measured on day 3 after the start of treatment, where under a defi ned value, was related to the success of the treatment [10]. In the study of Koivula et al. they confi rmed the usefulness of PCT in the diagnosis of bacteraemia and in differentiating Gram-negative bacteraemia from other causes of fever in neutropenia. Their study results indicate that haematology patients with elevated PCT should be treated with broad-spectrum coverage for Gram-negative microbes [7]. For patients with upper and lower respiratory tract infections, post-operative infections, and for severe sepsis patients in the ICU, randomized controlled trials have shown a benefi t of using PCT algorithms to guide decisions about initiation and/or discontinuation of antibiotic therapy [8]. Limitations of every PCT measurement include false-positive and false-negative results. Unspecifi c elevations in PCT levels in the absence of a bacterial infection can typically be seen in situations of massive cell death, for example after severe trauma or surgery [11]. In these situations, PCT values are usually only moderately elevated and show a rapid decline in follow-up measurements. Conversely, falsely low PCT levels, typically seen during the early course or localized states of an infection, often show an increase in the follow-up measurements. Therefore, highly sensitive PCT assays are required, as Sc an d J In fe ct D is D ow nl oa de d fr om in fo rm ah ea lth ca re . c om b y SU N Y S ta te U ni ve rs ity o f N ew Y or k at S to ny B ro ok o n 10 /3 0/ 14