Clinical impact of a PCR-based assay for pathogen detection in critically ill patients with evidence of infection

Introduction

Blood cultures are often negative even in patients with clinical signs of severe sepsis. Furthermore, the long time to result of culture-based methods does not allow the results to guide empiric antimicrobial therapy. PCR-based pathogen detection promises a higher rate of positivity and a faster time to result.

Objective

To report the performance of PCR-based pathogen detection compared with blood culture in ICU patients with evidence of infection, and the impact of this test on the antimicrobial therapy.

Methods

Patients treated on an interdisciplinary ICU were included into this observational study if a blood culture (BC) was drawn on discretion of the treating physician. Blood cultures and EDTA-blood were taken by sterile venous puncture. The EDTA-blood was processed with a PCR-based assay (VYOO^®; SIRS-Lab GmbH, Jena, Germany), which detects a panel of 34 bacterial and six fungal pathogens as well as five antibiotic resistances. Data are given as median and interquartile range.

Results

Sixty-three patients were included into this study. Age was 68.0 (55.5 to 74.0) years, APACHE II score was 17 (13 to 23), SOFA score at study inclusion was 10.0 (7.50 to 11.0), and ICU mortality was 33.3%. In 54 patients (84.3%) infection was either microbiologically confirmed or clinically proven. The baseline procalcitonin was 2.4 (0.8 to 8.0) ng/ml. Eighty-two pairs of BCs and PCRs have been drawn. Ten (12%) BCs and 30 (36.6%) PCRs were positive (P < 0.001). Time to test result was significantly shorter in the PCR than in the BC (Figure 1). Twelve positive PCR results (Figure 2, grey areas) prompted a change in antibiotic or antimicrobial therapy.

Figure 1

(abstract P9)

Figure 2

(abstract P9)

Conclusion

The PCR-based assay resulted in a considerably higher amount of positive results within a shorter time to result than the BC in this group of high-risk patients with evidence of infection. These data demonstrate that the shorter time to result may guide adjustment of antimicrobial therapy earlier than culture-based methods. Further studies are necessary to prospectively investigate the impact of the PCR technique on antimicrobial therapy and infection control.