LAUSR

Abstract Background Methicillin sensitive Staphylococcus aureus (MSSA) bacteremia is a highly lethal infection; first-line therapy with a β-lactam, commonly cefazolin, provides a significant mortality benefit over the second-line therapy, vancomycin, which is often used in patients reporting β-lactam allergy. Methods We designed a simulation model of inpatients aged 55–75 years with MSSA bacteremia and a self-reported history of β-lactam allergy. The model adopted a US health-system perspective, a lifetime horizon, and a willingness-to-pay threshold of $100,000 per quality-adjusted life year (QALY). We compared routine care (vancomycin), history screening (questionnaire assessing anaphylaxis history), and bedside penicillin skin testing. Incremental cost-effectiveness ratio (ICER) was measured using 2017 US dollars per QALY. Baseline co-morbid states (diabetes, malignancy, and end-stage renal disease [ESRD] requiring dialysis) were also modeled. Future costs and benefits were discounted at 3% per year. Results Among patients with MSSA bacteremia and a self-reported penicillin allergy, skin testing produced the best clinical outcomes and was cost-effective relative to history screening, generating 0.51 additional QALYs at an ICER of $22,062 per QALY gained. Among patients with diabetes, malignancy, or ESRD, the ICER for skin testing relative to history screening increased to $30,830–$127,182, reflecting the overall lower life expectancy and high annual survivor healthcare cost in these higher risk groups. Results were robust to wide variations in the cost and diagnostic performance of skin testing: in sensitivity analyses, skin testing remained the optimal strategy when cost was <$5600, specificity >60%, and sensitivity >10%. Conclusion Among adults with MSSA bacteremia and a self-reported β-lactam allergy, skin testing is cost-effective relative to history screening and routine care at conventional willingness-to-pay thresholds and should be widely adopted given the mortality benefit of β-lactams over alternate antibiotics in MSSA bacteremia. Disclosures All authors: No reported disclosures.