Multiplex bacterial PCR in the bronchoalveolar lavage fluid of non-intubated patients with suspected pulmonary infection: a quasi-experimental study.

Background: Early pathogen identification in pulmonary infection is crucial to guide antibacterial therapy and decrease length of hospital stay. We hypothesise that compared to conventional diagnostic methods, a multiplex bacterial polymerase chain reaction assay has a higher diagnostic yield in bronchoalveolar lavage (BAL) fluid and improved clinical outcomes in patients with suspicion of pulmonary infection.

Methods: A prospective, monocentric, quasi-experimental, observational study was carried out. Unselected patients with suspected pulmonary infection who underwent bronchoscopy with BAL were included in the study over a period of 1 year. In addition to conventional diagnostic methods, a multiplex PCR bacterial assay was performed in BAL on a 2 week on: 1 week off pre-determined schedule. No therapeutic recommendations were provided to the treating physician.

Results: 605 cases were included, 54% of whom were immunosuppressed. Conventional diagnostic methods detected 56% of the bacteria evidenced by PCR. PCR failed to detect bacteria in 4% of the cases with a positive conventional diagnostic result. After bronchoscopy, 42% of the patients received antibacterial therapy for pulmonary infection for a median of 12 antibiotic days. There was no statistically significant difference in length of hospital stay (median 8 8; p=0.839), antibiotic exposure (median 11 14; p=0.362) or number of antibiotics prescribed (median 2 2; p=0.595) between the two groups.

Conclusions: A multiplex bacterial PCR detected more bacteria in BAL fluid than conventional diagnostic methods. However, without a specific antibiotic stewardship approach and a clear understanding of the clinical implications of a positive or negative PCR result, the PCR results did not influence clinical outcomes.