Can procalcitonin reflect the etiology of the bacteremia?

Background

An early diagnosis of bacteremia is crucial to facilitate adequate treatment of severe infections. We analyzed 5,564 blood cultures for a 3-year period (2004, 2005, 2006) with a 20% rate of positive blood culture, and observed the increasing prevalence of Gram-positive bacteremia (45%/48%/63%, respectively). Classical clinical inflammatory signs of Gram-negative and Gram-positive infection are often similar, while some biomarkers may help in early diagnostic of the nature of pathogen before obtaining the blood culture results. The objective of the study was to estimate the value of procalcitonin (PCT) as a discriminate marker of Gram-positive and Gram-negative infection in suspected bacteremia patients.

Materials and methods

During 3 years monitoring of PCT and blood culture in a total of 150 episodes (113 cardiac patients with postoperative complication (systemic inflammatory response syndrome)) of positive blood culture with simultaneous PCT-test, results were registered and retrospectively analyzed. For blood culture we used the BacT/ALERT 3D system (bioMerieux, France) and the BBL CRYSTAL Identification Systems Enteric/Nonfermenter ID Kit (Becton Dickinson, USA). PCT concentrations were measured by immunoluminometric method (PCT LIA; B.R.A.H.M.S Aktiengesellschaft GmbH, Germany). The data were compared by Mann–Whitney U-test, and P < 0.05 was considered statistically significant. The data are expressed as the median and 25th and 75th percentiles.

Results

In our study, 101/150 (67%) clinically important bacteremia were caused by Gram-negative bacteria and 49 (33%) by Gram-positive pathogens. The serum PCT concentration (median) was significantly higher in the group of Gram-negative bacteremia patients than in the group of patients with Gram-positive bacteremia (5.40 versus 0.86 ng/ml, P < 0.001) (Table 1). A PCT level > 2 ng/ml was reported in 72/101 (71%) cases in Gram-negative bacteremia patients, whereas in patients with Gram-positive bacteremia this level of PCT was reported twofold lower (16/49 (32.6%) cases). The analysis of mortality in patients with systemic infection (PCT > 2 ng/ml + bacteremia) has shown comparable data in groups of patients with Gram-positive and Gram-negative bacteremia (8/14 (57.1%) and 31/55 (56.3%), respectively).

Table 1 Procalcitonin and clinical inflammatory signs in groups of patients with Gram-negative and Gram-positive bacteremia

Conclusion

A high PCT level in patients with suspected infection may be indicative of Gram-negative infection before obtaining the culture results.