Inter-rater concordance of wound classifications in patients undergoing appendectomy

Despite the widespread utilization of a four-stage wound classification system to risk-adjust operations for surgical site infection (SSI) rates, we are not aware of any study evaluating the definitions of the wound classes for clarity. We limited our study of wound classifications to appendectomies and posed the question whether different reviewers classify individual cases differently.

We evaluated the wound classifications of 105 consecutive appendectomies in our community hospital. Four reviewers graded retrospectively the wound classifications, first after reading the description of the appendix in the operative report and again after reading the pathology report. The wound classifications of the four reviewers were evaluated for concordance with the original operating room nurse (ORN) assignment.

The kappa scores for inter-observer concordance of wound classifications among the four reviewers based on their interpretation of the operative report and the ORN who originally classified the operation ranged from 0.1028 to 0.1597. By conventional standards, this represents no better than "slight agreement" for any of the reviewers. We found that 19%, 50%, 94%, 95%, or 96% of our appendectomies would be considered "high risk," Class 3 or 4, operations depending on which rater classified the operation. The additional information contained in the pathology reports did not change the distribution of wound classifications of the four reviewers significantly.

Our study demonstrated considerable differences in the distribution of wound classifications of appendectomies among our ORNs and retrospective reviewers. A review of the surgical literature supports our finding that the incision classification system utilized commonly lacks precision, at least in the rating of appendectomies. We recommend that further studies be performed to determine whether changes in the definitions of wound classes are warranted.