The clinical significance of procalcitonin to identifying microorganism strains in ICU patients with bloodstream infection

Objective To investigate the level of serum procalcitonin (PCT) for exploring the clinical value in identifying microorganism strains in the intensive care unit (ICU) patients with blood stream infections.Methods A retrospective analysis of patients with positive blood culture of a single strain and with serum PCT levels detected simultaneously was carried out from January 2010 through December 2012.The comparisons of PCT levels were done among Gram-negative (G-) bacteria,Gram-positive (G +) bacteria and fungi in patients with bloodstream infections.The diagnostic performance of PCT was determined by the receiver operating characteristic curve (ROC).Results A total of 524 patients with blood stream infection were enrolled and categorized into three different groups,namely G-bacteria infection group (n =206),G + bacteria infection group (n =276),and fungi infection group (n =42).The median value of PCT level of G-bacteria group was 14.9 ng/ml,which was significantly higher than that of the other two groups with 0.14 ng/ml and 1.76 ng/ml,respectively (P ＜ 0.01).Further,the PCT level of fungi group also obviously higher than that of G + bacteria group (P ＜ 0.001).According to ROC,PCT level at 2.11 ng/ml could distinguish G-bacteria infection from G + bacteria infection with sensitivity 82.8％ and specificity 80.1％,while PCT at 5.09 ng/ml was used to distinguish G-bacteria infection from fungi infection with sensitivity 68％ and specificity 73.8％.The area under the ROC of G + bacteria and fungi was 33.0％ (P ＜ O.01).Conclusions Serum PCT level is valid for distinguishing ICU patients with blood stream infection caused by G-bacteria from G+ bacteria or from fungi,but the validity of PCT for distinguishing G + bacteria from fungi infection needs to be set up by further studies. Key words: Procalcitonin;  ICU ;  Bloodstream infection ;  Microorganism types