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

Abstract

BackgroundEarly 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.MethodsA prospective, monocentric, quasi-experimental, observational study. During 1 year, unselected patients with suspected pulmonary infection who underwent bronchoscopy with BAL were included in the study. 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.Results605 cases were included with 54% 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 versus 8; p=0.839), antibiotic exposure (median 11 versus 14; p=0.362) or number of antibiotics prescribed (median 2 versus 2; p=0.595) between the two groups.ConclusionsA 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.

Gram-negative pulmonary infections – advances in epidemiology and diagnosis

“…Accordingly, the benefits of the test itself cannot be disambiguated from those subsequent to its active reporting to the requester [32 ▪ ,33 ▪ ]. This issue of ‘standalone’ multiplex PCR diagnostics without informed and expert subsequent advice may not lead to better outcomes or less antibiotic exposure [34].…”

Increased Alveolar Epithelial Damage Markers and Inflammasome-Regulated Cytokines Are Associated with Pulmonary Superinfection in ARDS

“…However, false negative rates vary among studies possibly due to the lack of a uniform threshold for positive BAL cultures. The use of RT-PCR was also mostly limited to virological testing while multiplex PCR, which has shown superior sensitivity for the detection of respiratory lower tract infections compared to quantitative bacterial cultures [48], has rarely been performed. Hence, the number of pulmonary superinfections may be underestimated in our study.…”

Multiplex bacterial PCR for antibiotic stewardship in pneumonia – Author's reply

“…Although, similar pathogen identification rates in bronchoalveolar lavage using cultures were previously shown, multiplex bacterial PCR can have a 47% higher positivity rate, which further complicates the distinction between colonising and infection causing bacteria. 5 Our hypothesis is that more rigorous inclusion criteria, such as radiological and serological features, led to the decrease of false positive PCR results in the Flagship II study. In addition to consolidation on chest imaging and evidence of systemic inflammation, more than half of the bronchoalveolar lavage specimens (106 of 198; 53%) showed neutrophilia on cytological examination in post-hoc analysis, suggesting the presence of bacterial infection in a high proportion of study participants.…”

“…Indeed, the performance of such assays is highly dependent on both the study population and reference standard. 5 In fact, Unyvero showed superior sensitivity compared with culture when taking clinical diagnosis of infection as the reference standard. 5 Due to the great interest in available assays, we also compared the performance of Curetis Unyvero and BioFire FilmArray in the bronchoalveolar lavage of 42 patients with a suspected lower respiratory tract infection.…”

“…5 In fact, Unyvero showed superior sensitivity compared with culture when taking clinical diagnosis of infection as the reference standard. 5 Due to the great interest in available assays, we also compared the performance of Curetis Unyvero and BioFire FilmArray in the bronchoalveolar lavage of 42 patients with a suspected lower respiratory tract infection. The patient cohort had a mean age of 67±2 years and 62% (26 of 42) were male.…”