Background: The purpose of this study is to compare techniques for the diagnosis of suspected ventilator-associated pneumonia in the trauma patient. Per the literature, bronchoscope protected brushings and bronchoalveolar lavage were set as the standards for comparison because of their high specificity and sensitivity. We hypothesized that blind protected brushings were equivalent to bronchoscope-directed techniques and that endotracheal aspirates (ETA) were not.
Methods: With informed consent, 90 trauma patients with two or more of the following were accepted into the study: 48 hours or more on the ventilator, new or increasing infiltrate on chest radiograph, excess or purulent secretions, suspected aspiration, temperature of 38.5 degrees C or above, white blood cell count greater than or equal to 12,000/mm3, and respiratory distress. Four samplings were performed on each patient using bronchoscope-assisted and nonbronchoscopic techniques. Each patient had cultures obtained by and significances quantified as follows: ETA, moderate/many/abundant; bronchoscope-directed protected brushings (BDPB), 103 colony-forming units [CFU]/mL; blind protected brushing via endotracheal tube (BPB), 103 CFU/mL; and bronchoscopic bronchoalveolar lavage (BAL), 104 CFU/mL. Quantitative cultures were obtained and compared for the following pathogens: gram-positive cocci, gram-positive rods, gram-negative cocci, gram-negative rods, anaerobic bacteria, and yeast. An assessment of agreement for cultured pathogens between the sampling modalities was completed using kappa (kappa) analysis, and significance was set at p < or = 0.05.
Results: With patients used as their own controls, Gram's stain and pathogens cultured from the various sampling techniques were compared for agreement by kappa analysis. BDPB and BAL were set as the "gold standards" for comparison against each other and against the BPB and ETA. Kappa analysis was used to measure the strength of agreement for these findings; individual values from the comparisons of Gram's stain were then averaged for descriptive purposes of the data. Most kappa values were associated with a statistically significant value of p < 0.05. The greatest strength of agreement was found to be moderate comparing Gram's stain results of BPB and BDPB (kappa = 0.467), ETA and BAL (kappa = 0.535), and BPB and BAL (kappa = 0.547). Fair kappa values were shown in comparing Gram's stain results of ETA and BDPB (kappa = 0.382) and BAL and BDPB (kappa = 0.390).
Conclusion: A quantitative analysis of bacteriologic cultures obtained by four standard sampling techniques has demonstrated with statistical significance that no difference exists between modality of sampling in reliability or in obtaining clinically significant pathogens. In reviewing the literature, this study is the first assessment of agreement for cultured pathogens between the four different sampling modalities and the largest to assess the efficacy of the blind protected brush technique.