A. P. Worden1, P. Kandagatla1, I. Rubinfeld1, A. Stefanou1 1Henry Ford Health System/Wayne State University,Surgery,Detroit, MICHIGAN, USA
Introduction: Wound class helps predict wound related complications and is useful for stratifying surgical site infection (SSI) reporting. Misclassification could be significant as report cards increasingly affect reimbursement and publicly reported data. We sought to evaluate misclassification among commonly performed surgeries that are defined to be clean-contaminated or higher. We hypothesized that rates of misclassification are increasing, and this increasing trend may be correlated with laparoscopic approaches.
Methods: The National Surgical Quality Improvement Program (NSQIP) database was queried from 2005-2016 by CPT codes identifying common surgeries that are by definition not clean: colectomy, cholecystectomy, hysterectomy, and appendectomy. Misclassification was defined as a procedure classified as clean. Obtained information included year of surgery, pre-operative patient characteristics, intra-operative characteristics, laparoscopic vs open approach, wound complications, readmission, and mortality. Variables were compared between correctly and incorrectly classified patients. Multivariate logistic regression was performed to derive independent predictors of misclassification.
Results: We reviewed 789,221 cases, of which 17,696 (2.29%) were misclassified as clean. There were 75,684 colectomies (16,749 laparoscopic and 58,935 open), 374,564 cholecystectomies (347,894 laparoscopic and 26,670 open), 65,3940 hysterectomies (15,089 laparoscopic and 63,8851 open) and 25,6905 appendectomies (24,8491 laparoscopic and 8,414 open). Misclassification was associated with the type of procedure (p<0.01). Hysterectomy was the most commonly misclassified procedure (4.8%), and colectomy the most accurately classified (0.8%). Misclassification was lower in laparoscopic cases (2.1% vs 2.7%, p<0.01).
Misclassified cases increased from 2005 to 2016 (0.2% vs 3.7%, p<0.01). Misclassified patients were younger (46.7 vs 47.7 years, p<0.01) and had lower rates of HTN (27.7% vs 30.4%, p<0.01), COPD (2.0% vs 2.7%, p<0.01), smoking history (17.1% vs 18.8%, p<0.01), and steroid use (1.7% vs 3.0%, p<0.01). Post-operatively, misclassified patients had lower rates of Clavien 4 complications (1.0% vs 2.7%, p<0.01), shorter length of stay (2.2 vs 3.2 days, p<0.01), and 30-day readmission (3.7% vs 5.0%, p<0.01). The rate of any SSI is decreased in misclassified patients (1.7% vs 3.4%, p<0.01). Open hysterectomy was the most significant positive predictor for misclassification (OR 3.34, p<0.01), while open appendectomy was the most significant negative predictor (OR 0.20, p<0.01).
Conclusion: Despite guidelines, there is an increasing trend of wound misclassification. Given that misclassified patients have better outcomes, misclassification may be affected by patient characteristics, operative approach, and type of procedure, rather than reflecting the true infectious burden. Further research is warranted to explore this phenomenon.