INTRODUCTION: Hysterectomy is a clean-contaminated procedure, and surgical site infections (SSIs) remain a common, costly complication. Recent evidence suggests adding anaerobic coverage with metronidazole to cefazolin reduces SSIs. OBJECTIVE: Evaluate the 1-year cost-effectiveness of cefazolin + metronidazole versus cefazolin alone for hysterectomy prophylaxis. METHODS: A decision-analytic model compared cefazolin alone to cefazolin + metronidazole. SSI risks were taken from published cohort data: cefazolin (overall 4. 7%; superficial 2. 6%, deep 0. 58%, organ/space 1. 48%) vs cefazolin + metronidazole (overall 2. 6%; superficial 1. 69%, deep 0. 00%, organ/space 0. 91%). Costs (USD) applied per SSI type were superficial 9, 546, deep 3, 345, organ/space 20, 458; metronidazole added 2. Health outcomes used EQ-5D utility decrements with piecewise weighting across 12 months: superficial (−0. 09, −0. 11, −0. 06 for <4, 4–9, 9–12 months) and deep/organ-space (−0. 10, −0. 12, −0. 08). Outcomes were expected costs, QALYs, incremental cost, incremental QALYs, ICER, and net monetary benefit (NMB) from a healthcare perspective over 1 year. Uncertainty was assessed with one-way sensitivity (tornado) and probabilistic sensitivity analysis (PSA; 5, 000 simulations). Adverse events from metronidazole were explored in sensitivity analyses and had no qualitative impact on conclusions, so were omitted from the base case. RESULTS: Cefazolin + metronidazole reduced expected SSI by 2. 1 percentage points versus cefazolin alone. Expected cost/QALY were 2, 655 and 0. 9973 for cefazolin + metronidazole vs 3, 024 and 0. 9966 for cefazolin alone, yielding ΔCost −369 and ΔQALY +0. 0007 per patient; combination prophylaxis was dominant. Per 10, 000 hysterectomies, this translated to 206 fewer infections and 2. 2 million saved. PSA showed cefazolin + metronidazole was cost-effective in 94–95% of simulations across willingness-to-pay thresholds of 50, 000–150, 000/QALY. One-way sensitivity identified SSI probabilities and organ/space infection cost as the primary drivers; the preferred strategy did not change across ranges tested. CONCLUSIONS: Adding metronidazole to cefazolin for hysterectomy prophylaxis reduces infections, improves QALYs, and lowers costs at 1 year. Findings are robust to extensive sensitivity analyses, supporting combination prophylaxis as a cost-effective standard of care. Figure 1Figure 2Table 1
Cevigney et al. (Fri,) studied this question.