Incidence of Surgical Site Infection Following Mastectomy With and Without Immediate Reconstruction Using Private Insurer Claims Data

Abstract

Objective The National Healthcare Safety Network classifies breast operations as clean procedures with an expected 1–2% surgical site infection (SSI) incidence. We assessed differences in SSI incidence following mastectomy with and without immediate reconstruction in a large, geographically diverse population. Design Retrospective cohort study. Patients Commercially-insured women aged 18–64 years with ICD-9-CM procedure or CPT-4 codes for mastectomy from 1/1/2004–12/31/2011. Methods Incident SSIs within 180 days after surgery were identified by ICD-9-CM diagnosis codes. The incidence of SSI after mastectomy +/− immediate reconstruction was compared by the chi-square test. Results From 2004–2011, 18,696 mastectomy procedures among 18,085 women were identified, with immediate reconstruction in 10,836 (58%) procedures. The 180-day incidence of SSI following mastectomy with or without reconstruction was 8.1% (1,520/18,696). Forty-nine percent of SSIs were identified within 30 days post-mastectomy, 24.5% between 31–60 days, 10.5% between 61–90 days, and 15.7% between 91–180 days. The incidence of SSI was 5.0% (395/7,860) after mastectomy-only, 10.3% (848/8,217) after mastectomy plus implant, 10.7% (207/1,942) after mastectomy plus flap, and 10.3% (70/677) after mastectomy plus flap and implant (p<0.001). The SSI risk was higher after bilateral compared with unilateral mastectomy with (11.4% vs. 9.4%, p=0.001) and without (6.1% vs. 4.7%, p=0.021) immediate reconstruction. Conclusions SSI incidence was two-fold higher after mastectomy with immediate reconstruction than after mastectomy alone. Only 49% of SSIs were coded within 30 days after operation. Our results suggest stratification by procedure type will facilitate comparison of SSI rates after breast operations between facilities.

Development of a Risk Prediction Model to Individualize Risk Factors for Surgical Site Infection After Mastectomy

“…In previous studies, immediate implant reconstruction was associated with increased risk of SSI compared to mastectomy 19;23 and flap reconstruction, 8 however immediate pedicled and free transverse rectus abdominis flap reconstructions were associated with increased risk of SSI compared to implant reconstruction in another study. 14 We previously reported higher risk of SSI after mastectomy with immediate reconstruction compared with mastectomy-only and after bilateral versus unilateral mastectomy using these same data, 25 and others have reported increased wound complications 42 or SSI 23 associated with bilateral versus unilateral mastectomy. Home health care was associated with decreased risk of SSI in the derivation model, controlling for other risk factors for infection.…”

“…The mastectomy patient population was further refined as reported previously. 25 We implemented steps to increase the likelihood that the procedures were truly mastectomies, excluding claims containing CPT-4, HCPCS, or UB-04 revenue codes truncated to 4 digits and populated in the fields reserved for ICD-9-CM procedure codes, and claims in which a mastectomy procedure code was present only on one line on a single claim with no other claims on the same date. We also excluded mastectomy procedures that were more consistent with breast-conserving surgery (BCS) when both were coded during the same admission.…”

“…25 NIWCs included fat necrosis (567.82, 611.3), dehiscence (875.0, 875.1, 879.0, 879.1, 998.3, 998.32), hematoma (998.12), and necrosis (998.83). We censored the observation period to capture SSIs at the time of a subsequent breast or non-breast NHSN procedure.…”

“…We censored the observation period to capture SSIs at the time of a subsequent breast or non-breast NHSN procedure. 25 Since risk factors for SSIs and NIWCs may be similar, we excluded persons who did not have an SSI but did have an NIWC in risk factor analyses so that the comparison group was wound complication-free.…”

“…We identified cancer stage using ICD-9-CM diagnosis codes on pathology claims, when available, as described previously. 25;34 Potential operative risk factors included unilateral versus bilateral mastectomy, 25 immediate breast implant and/or flap reconstruction, 25 sentinel node, and simple versus modified radical mastectomy (Appendix Table 1). …”