Diagnostic Performance and Impact of a Multiplex PCR Pneumonia Panel in ICU Patients With Severe Pneumonia.

Primary outcomes

1. The rate of diagnostic concordance between Classical microbiological cultures and the respiratory multiplex PCR (RM-PCR) and conventional microbiological cultures (CMC) to identify pathogens responsible for severe pneumonia in critically ill patients.

   Time frame: through study completion, an average of 6 months

   Classical microbiological cultures (CMC) will serve as the gold standard for the comparison between techniques, considering a test result:

   • A true positive, when CMC and RM-PCR have identified the same microorganism (CMC+, PCR-RM +).
   • A false positive, when RM-PCR detected an organism but not CMC (CMC-, RM-PCR+)
   • A true negative, when no method detected any microorganism (CMC-, RM-PCR -)
   • A false negative, when CMC but not RM-PCR has detected an organism (CMC+, RM-PCR -).

   Sensitivity, specificity, and positive and negative predictive values for the respiratory multiplex PCR will be calculated using the precedent findings.

2. The impact of the respiratory multiplex PCR (RM-PCR) on the appropriateness of empirical antimicrobial therapy.

   Time frame: through study completion, an average of 6 months

   The proportion of patients for whom the respiratory multiplex PCR (RM-PCR) induces an appropriate change of antibiotic therapy. Appropriate changes include adequacy, de-escalation, and escalation of antibiotic treatment.

   • Adequacy is defined as introducing an antibiotic to cover a microorganism that was not adequately treated before the results of RM-PCR.
   • Escalation is defined by a widening of the ATB spectrum to cover a pathogen not taken into account or the detection of resistance genes.
   • De-escalation is defined as the use of a narrower-spectrum anti-infective or the discontinuation of an ATB combination.