# Retrospective Evaluation of the Efficacy of Prophylactic Antibiotics in Preventing Surgical Site Infections in Elliptical Skin Biopsy

## TL;DR

A study found that using antibiotics before elliptical skin biopsies does not reduce infection risk, suggesting they may be unnecessary.

## Contribution

This is the first retrospective evaluation of prophylactic antibiotic efficacy in preventing SSIs after elliptical skin biopsy.

## Key findings

- SSI rates were similar between patients receiving prophylactic antibiotics and those who did not.
- Experienced clinicians were less likely to prescribe prophylactic antibiotics.
- Antibiotic use was modestly associated with higher serum albumin levels, but this likely lacks clinical relevance.

## Abstract

Introduction: Elliptical skin biopsy is a commonly performed dermatologic procedure that provides sufficient tissue for histopathologic diagnosis and additional testing. However, concerns remain regarding the risk of surgical site infection (SSI), leading to the widespread use of prophylactic antibiotics despite the lack of clear supporting evidence. This study aimed to evaluate whether prophylactic antibiotic administration reduces SSI risk following elliptical biopsy.

Methodology: A retrospective observational study was conducted at the University of Toyama, including 202 patients who underwent elliptical biopsy between October 2022 and July 2024. Among them, 146 (72.3%) received prophylactic antibiotics, while 56 (27.7%) did not. The primary outcome was the incidence of SSI within 30 days post procedure. Multivariable logistic regression and inverse probability of treatment weighting (IPTW) were applied to adjust for potential confounders.

Results: SSI occurred at similar rates in both groups (prophylactic vs. non-prophylactic: 11.0% vs. 10.7%, p = 1.0), suggesting that antibiotic prophylaxis may not be effective in reducing infection risk. Neither multivariable logistic regression nor IPTW analysis demonstrated a significant association between prophylactic antibiotic use and SSI prevention. Additionally, clinicians with more years of experience were less likely to prescribe prophylactic antibiotics, indicating greater confidence in withholding antibiotics when not clinically necessary. In contrast, higher serum albumin levels were associated with greater antibiotic use. Although this association reached statistical significance, the actual difference in albumin levels (4.1 vs. 3.8 g/dL) is modest and likely lacks clinical relevance. These findings suggest that antibiotic prescribing may have been influenced more by physician discretion, particularly among less experienced clinicians, as well as by institutional practices, routine habits, or excessive concern about SSI risk, rather than by objective indicators of clinical need.

Conclusion: These findings suggest that routine prophylactic antibiotic use after elliptical biopsy may not be necessary in dermatologic practice. Given increasing concerns about antimicrobial resistance and antibiotic shortages, optimizing antibiotic use is a critical consideration. Emphasizing alternative strategies, such as meticulous wound irrigation, postoperative care, and patient education, may help minimize SSI risk while ensuring safe wound healing. Further prospective studies with larger cohorts and standardized treatment protocols are warranted to confirm these findings.