1061. Comparison of the Acute Physiology and Chronic Health Evaluation (APACHE) II Score and the Pitt Bacteremia Score to Predict Mortality in Methicillin-Resistant Staphylococcus aureus Bacteremia

BACKGROUND: Methicillin-resistant Staphylococcus aureus bloodstream infection (MRSA BSI) is associated with high morbidity and mortality. The prediction of outcomes may have a profound impact on clinical decision making and risk stratification. The Acute Physiology and Chronic Health Evaluation (APACHE) II Score and the Pitt Bacteremia Score (PBS) have been repeatedly described as independent predictors of mortality in MRSA BSI. The APACHE II is complex to calculate and many of the variables may not be pertinent to MRSA BSI. The PBS is a simple score using readily assessable variables. The comparative predictive performance of the two models in MRSA BSI has not been evaluated. METHODS: Retrospective, observational, singe-center cohort study in adults with MRSA BSI between 2008 and 2018. Patients who did not receive active therapy ≤72 hours of index culture were excluded. APACHE II and PBS were calculated using the worst physiological values recorded ≤24 hours of blood culture collection. Discriminatory ability for 30-day mortality was assessed using the c-statistic and was compared using the Hanley and McNeil method. The best cut-off point in each scoring system was determined using the Youden Index (J). RESULTS: A total of 455 patients were included. The median (IQR) PBS and APACHE II were 2 (0, 3) and 18 (11, 23), respectively. All-cause 30-day mortality was 16.3%. The c-statistic (95% CI) for the APACHE II vs. PBS in the overall cohort and stratified by ICU status were: 0.813 (0.763, 0.863) vs. 0.717 (0.653, 0.782), P = 0.0035; ICU 0.729 (0.610, 0.848) vs. 0.570 (0.442, 0.699), P = 0.026; and non-ICU 0.821 (0.761, 0.881) vs. 0.700 (0.614, 0.786),P = 0.0046, respectively. The APACHE II with the maximum J value was 21; sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for 30-day mortality were 81.08%, 72.97%, 36.81%, and 95.21%, respectively. The PBS with the maximum J value was 3; sensitivity, specificity, PPV, and NPV were 66.22%, 72.18%, 31.61%, and 91.67%, respectively. CONCLUSION: The APACHE II was superior to the PBS in predicting 30-mortality in patients with MRSA BSI in the overall cohort and stratified by ICU status at BSI onset. Future research to develop a more practical scoring model with high discriminatory power is needed. DISCLOSURES: M. J. Rybak, Allergan: Consultant, Grant Investigator and Speaker’s Bureau, Research grant and Research support. Achaogen: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Bayer: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Melinta: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Merck: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Theravance: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Sunovian: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Zavante: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. NIAID: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support.