363. Individualizing Risk Factors for Surgical Site Infection after Mastectomy
Session: Poster Abstract Session: HAI: Surgical Site Infections
Thursday, October 8, 2015
Room: Poster Hall
Background: Few studies have examined risk factors for surgical site infection (SSI) following mastectomy. We developed a risk prediction model for SSI following mastectomy in a large, geographically diverse population.

Methods: We used commercial claims data to establish a retrospective cohort of women 18–64 years old with mastectomy from 2004–2011. ICD-9-CM diagnosis codes were used to identify SSIs and non-infectious wound complications (NIWCs) within 180 days after surgery. Risk factors for SSI were determined using multivariable logistic regression comparing women with SSI to those without SSI or NIWC. The derivation model was created using procedures from 2004–2008 and validated using procedures from 2009–2011.

Results: From 2004–2011 991 SSIs were identified after 11,973 operations (8.3%). Independent risk factors for SSI included rural residence (odds ratio [OR] 1.35; 95% confidence interval [CI] 1.06, 1.70), rheumatologic disease (OR 1.81; 95% CI 1.05, 3.09), depression (OR 1.52; 95% CI 1.09, 2.12), diabetes (OR 2.16; 95% CI 1.63, 2.87), hypertension (OR 1.48; 95% CI 1.23, 1.79), liver disease (OR 3.65; 95% CI 1.48, 8.97), obesity (OR 1.57; 95% CI 1.12, 2.19), pneumonia or urinary tract infection in the month before surgery (OR 1.60; 95% CI 0.97, 2.66), smoking (OR 1.29; 95% CI 0.99, 1.68), and smoking-related diseases (e.g., lung cancer/COPD; OR 2.23; 95% CI 1.50, 3.31). Operative risk factors included bilateral mastectomy (OR 1.39; 95% CI 1.16, 1.67), immediate implant (OR 1.83; 95% CI 1.52, 2.21), and flap reconstruction (OR 2.01; 95% CI 1.60, 2.51). Home health care was associated with lower risk of SSI (OR 0.78; 95% CI 0.63, 0.98). The model performed equally in the validation cohort per discrimination (C statistic=0.657 for derivation, 0.649 for validation) and calibration (Hosmer-Lemeshow P=0.091 for derivation, 0.462 for validation) measures.

Conclusion: We developed a novel risk prediction model for SSI after mastectomy. Although many of the identified factors are non-modifiable, they should impact pre-operative counseling and the consent process, particularly regarding the advantages/disadvantages of adding immediate reconstruction. Verification of our finding of decreased risk of SSI associated with home health is needed.

Margaret A. Olsen, PhD, MPH1,2, Katelin B. Nickel, MPH2, Julie A. Margenthaler, MD3, Ida K. Fox, MD4, Anna E. Wallace, MPH5 and Victoria J. Fraser, MD, FIDSA, FSHEA2, (1)Division of Public Health Sciences, Washington University School of Medicine, St. Louis, MO, (2)Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO, (3)Division of General Surgery, Washington University School of Medicine, St. Louis, MO, (4)Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO, (5)HealthCore, Inc., Wilmington, DE

Disclosures:

M. A. Olsen, None

K. B. Nickel, None

J. A. Margenthaler, None

I. K. Fox, None

A. E. Wallace, None

V. J. Fraser, None

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