Bronchoalveolar lavage amylase is associated with risk factors for aspiration and predicts bacterial pneumonia

OBJECTIVES: Aspiration of oropharyngeal or gastric contents into the respiratory tract leads to a spectrum of disorders with high morbidity. Aspiration is a diagnostic dilemma, because clinical characteristics and diagnostic tests are not effective predicting or confirming aspiration. We sought to determine whether α-amylase, a protein secreted by salivary glands and the pancreas, is elevated in bronchoalveolar lavage specimens in patients with clinical risk factors for aspiration and whether bronchoalveolar lavage amylase predicts bacterial pneumonia. DESIGN: Retrospective analysis. SETTING: Five adult ICUs at a tertiary care urban medical center. PATIENTS: Mechanically ventilated patients who underwent either bronchoscopic or nonbronchoscopic bronchoalveolar lavage within 72 hrs of endotracheal intubation between August 1, 2008 and June 30, 2010. MEASUREMENTS AND MAIN RESULTS: A total of 296 bronchoalveolar lavage amylase results from 280 patients were included in the analysis, and 155 bronchoalveolar lavage amylase specimens were obtained from patients with at least one predefined preintubation risk factor (altered consciousness, swallowing dysfunction, difficult intubation, peri-intubation vomiting, or cardiac arrest). Bronchoalveolar lavage amylase concentration increased as the number of preintubation risk factors increased (p < 0.001). In addition, bronchoalveolar lavage amylase was elevated in patients with bacterial pneumonia (cfu/mL ≥ 10) (p < 0.001). The area under the receiver operator curve for the ability of bronchoalveolar lavage amylase to differentiate between positive and negative bronchoalveolar lavage culture was 0.67 (95% confidence interval, 0.60-0.75). The lower 95% confidence interval for bronchoalveolar lavage amylase in patients with at least one preintubation risk factor for aspiration was 125.9 units/L. In multivariate analysis, bronchoalveolar lavage amylase < 125 units/L was associated with significantly lower odds of bacterial pneumonia (odds ratio 0.39, 95% confidence interval 0.21-0.71, p = 0.002). CONCLUSIONS: Elevated bronchoalveolar lavage amylase is associated with risk factors for aspiration and may predict bacterial pneumonia. Bronchoalveolar lavage amylase may be useful as an early screening tool to guide management of patients suspected of aspiration.