Can we define surgical site infection accurately in colorectal surgery?

Increasingly, surgical site infection (SSI) is being tied to quality of care. The incidence of SSI after colorectal surgery differs widely. We hypothesize that it is difficult to define SSI reliably and reproducibly when adhering to the U.S. Centers for Disease Control and Prevention (CDC) definitions.

Elective intra-abdominal colorectal procedures via a clean-contaminated incision performed at a single institution between January 1 and May 1, 2011 were queried. Three attending surgeons examined all patients' records retrospectively for documentation of SSI. These data were compared with the institutional National Surgeon Quality Improvement Program (NSQIP) data with regard to deep and superficial incisional SSI.

Seventy-one cases met the inclusion criteria. There were six SSIs identified by NSQIP, representing 8.4% of cases. Review of the three attending surgeons demonstrated a significantly higher incidence of SSI, at 27%, 38%, and 23% (p=0.002). The percent of overall agreement between all reviewers was 82.16 with a kappa of 0.64, indicating only modest inter-rater agreement. Lack of attending surgeon documentation and subjective differences in chart interpretation accounted for most discrepancies between the surgeon and NSQIP SSI capture rates.

This study highlights the difficulty in defining SSI in colon and rectal surgery, which oftentimes is subjective and difficult to discern from the medical record. According to these preliminary data from our institution, there is poor reliability between clinical reviewers in defining SSI on the basis of the CDC criteria, which has serious implications. The interpretation of clinical trials may be jeopardized if we cannot define SSI accurately. Furthermore, according to current CDC definitions and infection tracking strategies, these data suggest that the institutional incidence of SSI may not be a reliable measure by which to compare institutions. Better methods for defining SSI should be implemented if these data are made publicly available and tied to performance measures.