Multicenter validation of American Association for the Surgery of Trauma grading system for acute colonic diverticulitis and its use for emergency general surgery quality improvement program

The American Association for the Surgery of Trauma (AAST) has developed a new grading system for uniform description of anatomic severity of emergency general surgery (EGS) diseases, ranging from Grade I (mild) to Grade V (severe). The purpose of this study was to determine the relationship of AAST grades for acute colonic diverticulitis with patient outcomes. A secondary purpose was to propose an EGS quality improvement program using risk-adjusted center outcomes, similar to National Surgical Quality Improvement Program and Trauma Quality Improvement Program methodologies. This was a retrospective study of 1,105 patients (one death) from 13 centers. At each center, two reviewers (blinded to each other's assignments) assigned AAST grades. Interrater reliability was measured using κ coefficient. Relationship between AAST grade and clinical events (complications, intensive care unit use, surgical intervention, and 30-day readmission) as well as length of stay was measured using regression analyses to control for age, comorbidities, and physiologic status at the time of admission. Final model was also used to calculate observed-to-expected (O-E) ratios for adverse outcomes (death, complications, readmissions) for each center. Median age was 54 years, 52% were males, 43% were minorities, and 22% required a surgical intervention. Almost two thirds had Grade I or II disease. There was a high level of agreement for grades between reviewers (κ = 0.81). Adverse events increased from 13% for Grade I, to 18% for Grade II, 28% for Grade III, 44% for Grade IV, and 50% for Grade V. Regression analysis showed that higher disease grades were independently associated with all clinical events and length of stay, after adjusting for age, comorbidities, and physiology. O-E ratios showed statistically insignificant variations in risk of death, complications, or readmissions. AAST grades for acute colonic diverticulitis are independently associated with clinical outcomes and resource use. EGS quality improvement program methodology that incorporates AAST grade, age, comorbidities, and physiologic status may be used for measuring quality of EGS care. High-quality EGS registries are essential for developing meaningful quality metrics. Prognostic study, level V.