Will polymerase chain reaction (PCR)-based diagnostics improve outcome in septic patients? A clinical view.

Polymerase chain reaction (PCR)-based techniques allow more rapid and sensitive detection of pathogens compared with conventional blood culture. Nevertheless, the climate of opinion of relevant studies is that currently PCR can supplement but not replace blood culture. In numerous studies, combined detection rate of both methods was significantly higher compared with PCR or blood culture alone. Also, complete determination of antibiotic resistance can currently be performed only by blood culture. Further increase of the panel of multiplex PCR is complicated, because the vast majority of sepsis pathogens are already included, primer interactions leading to primer heteromers limit the amount of targets detectable within one PCR tube, and an array of too many individual PCR reactions for investigation of a single specimen leads to high cost and workload. Except for diagnostics of patients in whom unusual, not culturable, or fastidious pathogens are detected more often, such as immunosuppressed patients with suspected parasitic infection, etc., it might even not be necessary to further increase the spectrum of detectable species. If the primary aim of PCR diagnostics is to decrease inappropriate empirical treatment and improve patient outcome, detection should focus on those pathogens or resistance determinants that are not covered by guideline-recommended treatment regimens and that have been identified as the major cause of inappropriate treatment according to current studies. In our opinion, such a narrower assay is more cost effective, may achieve higher accuracy due to reduced intratest interference, and would better address current and emerging clinical needs.