Risk Factors for Death in Elderly Emergency Department Patients with Suspected Infection

OBJECTIVES To identify independent risk factors for death in elderly emergency department (ED) patients admitted for infection and to derive and validate a mortality-prediction rule for such patients. DESIGN Prospective cohort study. SETTING Tertiary hospital ED with 55,000 annual visits. PARTICIPANTS ED patients aged 65 and older admitted for infection between December 2003 and September 2004 in the derivation cohort and October 2005 and October 2006 in the validation cohort. MEASUREMENTS Primary outcome: 28-day in-hospital mortality. Data were extracted from charts, and multivariate logistic regression were performed to identify independent mortality predictors. A prediction model was constructed and then validated in a second cohort. RESULTS Nine hundred thirty-five patients were included in the derivation cohort and 2,015 in the validation cohort. Mortality was 6% in the derivation cohort and 7% in the validation cohort. In the derivation cohort, logistic regression revealed five independent mortality predictors: respiratory compromise (respiratory rate > 20 breaths per minute or hypoxemia) (odds ratio (OR)=4.0, 95% confidence interval (CI)=1.7-9.4), tachycardia (heart rate >= 120 betas per minute; OR=3.2, 95% CI=1.6-6.3), cardiovascular failure (systolic blood pressure < 90 mmHg despite fluid challenge or lactate >= 4.0; OR=9.0, 95% CI=4.7-17), preexisting terminal illness (OR=5.7, 95% CI=2.2-15), and platelet count less than 150,000/mm(3) (OR=2.7, 95% CI=1.3-5.6). Mortality increased with the number of factors: 0.51% for no factors, 3.1% for one factor, 14% for two factors, 47% for three or more risk factors. The c-statistic was 0.87 for the derivation model and 0.74 for the validation model. Almost 80% of patients in both cohorts were in low-risk groups (0 or 1 factor). CONCLUSION A rule derived from five readily available variables predicts mortality in infected elderly ED patients and allows identification of a large low-risk subgroup.