Methicillin sensitive Staphylococcus aureus (MSSA) bacteremia is a highly lethal infection; first-line therapy with a beta-lactam, commonly cefazolin, provides a significant mortality benefit over the second-line therapy, vancomycin, which is often used in patients reporting beta-lactam allergy.
We designed a simulation model of inpatients aged 55-75 years with MSSA bacteremia and a self-reported history of beta-lactam allergy. The model adopted a U.S. 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.
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%.
Among adults with MSSA bacteremia and a self-reported beta-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 beta-lactams over alternate antibiotics in MSSA bacteremia.
L. G. Winston, None
D. Kazi, None