Hospital-based acute care after outpatient colonoscopy: Implications for quality measurement in the ambulatory setting

Introduction: Ambulatory surgery centers now report immediate hospital transfer rates as a measure of quality. For patients undergoing colonoscopy, this measure may fail to capture adverse events, which occur after discharge yet still require a hospital-based acute care encounter. Objective: We conducted this study to estimate rates of immediate hospital transfer and hospital-based acute care following outpatient colonoscopy performed in ambulatory surgery centers. Research Design and Subjects: Using state ambulatory surgery databases from the 2009-2010 Healthcare Cost and Utilization Project, we identified adult patients who underwent colonoscopy. Immediate hospital transfer and overall acute health care utilization in the 14 days following colonoscopy was determined from corresponding inpatient, ambulatory surgery, and emergency department databases. To compare rates across centers while accounting for differences in patient populations, we calculated risk-standardized rates using hierarchical generalized linear modeling. Results: The final sample included 1,137,381 colonoscopy discharges from 1019 centers. At the ambulatory surgery center level, the median risk-standardized hospital transfer rate was 0.0% (interquartile range=0.0%), whereas the hospital-based acute care rate was 2.1% (interquartile range=0.6%), with few centers (N=36) having no observed encounters. No correlation was noted between the risk-standardized hospital transfer and hospital-based acute care rates (volume weighted correlation coefficient=0.04, P=0.16). Conclusions: Patients more frequently experience hospital-based acute care encounters after colonoscopy than the need for immediate hospital transfer. Broadening existing quality measures to include hospital-based acute care in the postdischarge period may provide a more complete measure of quality.