Predictors of lung infection among hospitalized patients undergoing bronchoalveolar lavage

STUDY OBJECTIVE: To identify predictors of lung infection and mortality among hospitalized patients with undiagnosed pulmonary infiltrates undergoing bronchoalveolar lavage (BAL). DESIGN: Prospective cohort study. SETTING: Barnes-Jewish Hospital, St Louis, a university-affiliated teaching hospital. PATIENTS: Eighty-two consecutive hospitalized patients with undiagnosed pulmonary infiltrates. INTERVENTIONS: BAL, prospective patient surveillance, and data collection. MEASUREMENTS and RESULTS: Forty-seven (57.3%) patients were classified as having a lung infection based on microbiologic cultures or special stains of BAL fluid and/or histologic examination of lung tissue specimens. The remaining 35 (42.7%) patients were classified as having a noninfectious etiology as the cause of their pulmonary infiltrates. Multiple logistic regression analysis demonstrated that a concentration of endotoxin in BAL fluid > 5 EU/mL (adjusted OR = 22.3; 95% CI = 9.5 to 52.4; p < 0.001) was the only independent predictor of a final diagnosis of lung infection. A 'high' clinical suspicion for the presence of lung infection by the patient's attending physician (adjusted OR = 6.0; 95% CI = 2.2 to 16.6; p = 0.079) was the next best predictor variable identified. Lung infection was diagnosed in 93.5% of patients (n = 31) when both of these predictor variables were present, in 42.5% of patients (n = 40) having only 1 of these predictor variables present, and in 9.1% of patients (n = 11) with neither predictor variable present (p < 0.001). The presence of multiorgan dysfunction at the time of BAL was the most accurate determinant of hospital mortality (p < 0.001). The Lung Injury Score (adjusted OR = 2.1; 95% CI = 1.5 to 3.0; p = 0.037), severity of illness as assessed by APACHE II (adjusted OR = 1.5; 95% CI = 1.4 to 1.6; p < 0.001), and the presence of matrix metalloproteinases in BAL fluid (adjusted OR = 5.8; 95% CI = 3.2 to 10.6; p = 0.004) were independently associated with the development of multiorgan dysfunction. CONCLUSIONS: An elevated concentration of endotoxin in BAL fluid can predict the presence or absence of lung infection among hospitalized patients with undiagnosed pulmonary infiltrates.