Background We provide evidence to revise the Infectious Diseases Society of America (IDSA) diabetic foot infection classification by adding a separate tier for osteomyelitis and evaluating if moderate and severe infection criteria improve the classification’s ability to direct therapy and determine outcomes. Methods We retrospectively evaluated 294 patients with moderate and severe infections. Osteomyelitis was confirmed by bone culture or histopathology. Soft tissue infection (STI) was based on negative bone culture, magnetic resonance imaging, or single-photon emission computed tomography. We stratified STI and osteomyelitis using IDSA criteria for moderate and severe infections and compared outcomes and complications. Results Osteomyelitis patients had greater antibiotic duration (32.5 ± 46.8 vs 63.8 ± 55.1 days; P < .01), surgery frequency (55.5% vs 99.4%; P < .01), number of surgeries (2.1 ± 1.3 vs 3.3 ± 2.3; P < .01), amputations (26.3% vs 83.4%; P < .01), reinfection (38.0% vs 56.7%; P < .01), and length of stay (14.5 ± 14.9 vs 22.6 ± 19.0 days; P < .01). There were no differences in moderate and severe STI outcomes except for infection readmissions (46.2% vs 25.0%; P = .02), and acute kidney injury (31.2% vs 50.0%; P = .03). There were no differences in moderate and severe osteomyelitis except the number of surgeries (2.8 ± 2.1 vs 4.1 ± 2.5; P < .01) and length of stay (18.6 ± 17.5 vs 28.2 ± 17.7; P < .01). Conclusions The IDSA classification better reflects outcomes if risk categories are stratified by STI or osteomyelitis and moderate and severe infections are not categorized separately.

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