Surgical Wound Misclassification to Clean From Clean-Contaminated in Common Abdominal Operations

Wound classification helps predict wound-related complications and is useful in stratifying surgical site infection reporting. We sought to evaluate misclassification among commonly performed surgeries that are at least clean-contaminated.

The National Surgical Quality Improvement Program database was queried from 2005 to 2016 by Current Procedural Terminology codes identifying common surgeries that are, by definition, not clean: colectomy, cholecystectomy, hysterectomy, and appendectomy. Univariate analysis and multivariate logistic regression were performed.

Of the 1,208,544 operative cases reviewed, 22,925 (1.90%) were misclassified as clean. Hysterectomy was the most commonly misclassified operation (3.11%), and colectomy the least (0.82%). Misclassification was higher in laparoscopic cases (1.92% versus 1.82%; P < 0.01). Misclassification increased from 2005 to 2016 (0.22% versus 3.11%; P < 0.01). Misclassified patients were younger (46.7 versus 47.7 y; P < 0.01); had lower rates of hypertension, chronic obstructive pulmonary disease, smoking history, and steroid use (P < 0.01); and had shorter length of stay (2.2 versus 3.2 d; P < 0.01), lower 30-d readmission rates (3.7% versus 5.0%; P < 0.01), and less surgical site infections (1.7% versus 3.4%; P < 0.01). Open hysterectomy was the most significant positive predictor for misclassification (odds ratio 3.34; P < 0.01). Open appendectomy was the most significant negative predictor (odds ratio 0.20; P < 0.01).

There is an increasing trend of misclassifying wounds as clean. Misclassified patients have better outcomes, and misclassification may be affected by patient characteristics, operative approach, and type of procedure rather than reflecting the true infectious burden. Further research is warranted.