DIFFICULTY IN PREDICTING BACTEREMIA IN ELDERLY EMERGENCY PATIENTS

Study objectives: To characterize the clinical presentation and identify factors predictive of bacteremia in elderly patients. Design: Retrospective review of emergency department charts, hospital records, and microbiology reports. Setting: Community teaching hospital with annual ED census of 65,000 adults. Participants: Seven hundred fifty elderly patients (aged 65 to 99 years) who were evaluated by the emergency physician, had blood cultures obtained in the ED, and were hospitalized with a suspected infectious process during a 12-month period. Measurements: Records were analyzed for demographic information, underlying diseases, clinical presentation, laboratory findings, sources of infection, and causative organisms. Using contingency tables, 79 patients with positive blood cultures were compared with a random sample of 136 patients with sterile blood cultures to identify clinical variables significantly (P < .05) associated with bacteremia. Logistic regression analysis was performed with significant factors to develop a model to predict bacteremia. Sensitivity, specificity, and predictive values were calculated for the model. Main results: The prevalence of bacteremia was 10.6%. Escherichia coli was the most commonly isolated pathogen (29% of cases), and the urinary tract was the most common source of infection (44.3% of cases). Logistic regression analysis showed that altered mental status (odds ratio, 2.88; 95% confidence interval [CI], 1.52 to 5.50), vomiting (odds ratio, 2.63- 95% Cl, 1.16 to 6.15), and WBC band forms of more than 6% (0.06) (odds ratio, 3.50,- 95% CI, 1.58 to 5.27) were independent predictors of bacteremia. The presence of at least one of these three factors had a sensitivity of 0.85 (95% Cl, 0.75 to 0.92) and a specificity of 0.46 (95% Cl, 0.38 to 0.55) for predicting bacteremia in the study group. The positive predictive value was 0.16 (95% CI, 0.12 to 0.19) and the negative predictive value was 0.96 (95% Cl, 0.94 to 0.98) for the ED patient group that met inclusion criteria.