A tool based on objective data to identify patients at elevated risk of hospital-onset Staphylococcus aureus bacteremia: a nested case–control study

Abstract Objective: Identify patients at increased risk of hospital-onset Staphylococcus aureus (SA) bacteremia based on objective and routinely collected data on presentation to the emergency room (ER). Design: Nested case–control study. Setting: A large, inner city, tertiary care center between January 1, 2011 and August 31, 2020. Participants: 375 cases and 2,248 matched controls. Methods: All hospitalized persons ≥18 years, found to have SA bacteremia at least 48 hours after admission were matched to 1–12 controls on birth year, race/ethnicity, sex, and month and year of admission. Vital signs and lab results were coded as “low” or “high” based on laboratory definitions. Multivariable models identified patient characteristics associated with an increased risk of SA bacteremia. Results: SA bacteremia was associated with high aspartate aminotransferase (AST) (>35 u/L )(HR = 1.92, 95%CI (1.30, 2.83), P = .001), high creatinine (Cr) (>1.1 mg/dl) (HR = 1.91, 95% CI (1.28, 2.85), P = .200), high bicarbonate (CO2) (>30 mEq/L) (HR = 2.07, 95% CI (1.17, 3.64), P = .01), and high total protein (>8.3 g/dl) (HR = 2.14, 95% CI (0.99, 4.66), P = .05). Fifteen or more days of hospital stay was associated with an increased risk of SA bacteremia (HR = 6.23, 95% CI (4.84, 8.00), P < .001). Conclusions: A prediction tool applied on admission of hospital stay ≥15 days OR any elevated two of the following: AST, creatinine, CO2, or total protein has sensitivity between 57%–64% and specificity to between 65%–78%.