Systematic review of studies investigating ventilator associated pneumonia diagnostics in intensive care

Abstract

Background Ventilator-associated pneumonia (VAP) is an important diagnosis in critical care. VAP research is complicated by the lack of agreed diagnostic criteria and reference standard test criteria. Our aim was to review which reference standard tests are used to evaluate novel index tests for suspected VAP. Methods We conducted a comprehensive search using electronic databases and hand reference checks. The Cochrane Library, MEDLINE, CINHAL, EMBASE, and web of science were searched from 2008 until November 2018. All terms related to VAP diagnostics in the intensive treatment unit were used to conduct the search. We adopted a checklist from the critical appraisal skills programme checklist for diagnostic studies to assess the quality of the included studies. Results We identified 2441 records, of which 178 were selected for full-text review. Following methodological examination and quality assessment, 44 studies were included in narrative data synthesis. Thirty-two (72.7%) studies utilised a sole microbiological reference standard; the remaining 12 studies utilised a composite reference standard, nine of which included a mandatory microbiological criterion. Histopathological criteria were optional in four studies but mandatory in none. Conclusions Nearly all reference standards for VAP used in diagnostic test research required some microbiological confirmation of infection, with BAL culture being the most common reference standard used.

Composition and diversity analysis of the lung microbiome in patients with suspected ventilator-associated pneumonia

“…However, capturing and standardising clinical decisions such as these is inherently difficulty, particularly across multiple study sites. Consequently, quantitative culture while not perfect remains the most commonly used reference standard to evaluate novel index tests in VAP research [ 49 ]. Additionally, the inclusion of only patients with a clinical suspicion strengthens our standard and better reflects clinical practice; however, we recognise that a negative BALF culture might mis-represent patients and not definitively exclude VAP, especially if they have received antibiotics.…”

HAP and VAP after Guidelines

“…the systematic use of non-invasive samples is questionable in non-ventilated patients. 44 The superiority of BAL upon endotracheal aspirations or sputum is still not admitted in HAP when considering the impact on mortality. 45 Indeed, Ranzani et al studied 200 HAP admitted in Spanish ICUs, with 40% of BAL performed in non-intubated patients.…”

Clinical Value of Bronchoscopy in Acute Respiratory Failure

“…In patients with suspected ventilator-associated pneumonia (VAP) undergoing invasive mechanical ventilation (IMV), respiratory tract sampling is recommended before the introduction/change of antibiotics, with the exception of some specific situations (i.e., severe sepsis, multi-organ dysfunction, shock), in whom antibiotic-therapy should not be delayed and have to be started empirically, followed by de-escalation strategy driven by mi-crobiological results [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Bronchoscopic (e.g., BAL and/or PSB) and non-bronchoscopic samples (e.g., tracheo-bronchial aspiration or mini-BAL) are, respectively, the "invasive" "non-invasive" techniques applicable in patients with suspected VAP [14][15][16]. A cutoff in terms of bacterial growth count may discriminate between infection and colonization (i.e., PSB: 10 3 cfu/mL; BAL: 10 4 cfu/mL; endotracheal aspirates: 10 5 cfu/mL) according to the "quantitative" analysis, while the presence or absence of pathogenic germs is enough for the "qualitative" analysis [2].…”

“…A cutoff in terms of bacterial growth count may discriminate between infection and colonization (i.e., PSB: 10 3 cfu/mL; BAL: 10 4 cfu/mL; endotracheal aspirates: 10 5 cfu/mL) according to the "quantitative" analysis, while the presence or absence of pathogenic germs is enough for the "qualitative" analysis [2]. The sensitivities of bronchoscopic techniques vary largely between 51 and 100% in uncontrolled trials depending on a great heterogeneity in terms of gold standard for diagnosis, microbiological thresholds, employed techniques, and variable comparison to "non-invasive" techniques [1,[14][15][16][17][18][19][20][21][22][23][24][25][26][27]. A recent systematic review [16] including five RCTs analyzed a total of 1367 immuno-competent patients with suspected VAP; no significant differences merged in terms of mortality rates, variation of antibiotic choices, and duration of IMV and of ICU stay between either "quantitative" versus "qualitative" analysis or "invasive" versus "non-invasive" sampling diagnostic methods.…”

“…The sensitivities of bronchoscopic techniques vary largely between 51 and 100% in uncontrolled trials depending on a great heterogeneity in terms of gold standard for diagnosis, microbiological thresholds, employed techniques, and variable comparison to "non-invasive" techniques [1,[14][15][16][17][18][19][20][21][22][23][24][25][26][27]. A recent systematic review [16] including five RCTs analyzed a total of 1367 immuno-competent patients with suspected VAP; no significant differences merged in terms of mortality rates, variation of antibiotic choices, and duration of IMV and of ICU stay between either "quantitative" versus "qualitative" analysis or "invasive" versus "non-invasive" sampling diagnostic methods. According to the accumulated published data, the choice of diagnostic FBO has to be individually made case per case and if "non-invasive" techniques fail to identify a responsible organism [2].…”