A comparative study of quality outcomes in freestanding ambulatory surgery centers and hospital-based outpatient departments: 1997-2004

Research Objective. To compare quality outcomes from surgical procedures performed at freestanding ambulatory surgery centers (ASCs) and hospital-based outpatient departments (HOPDs). Data Sources. Patient-level ambulatory surgery (1997-2004), hospital discharge (1997-2004), and vital statistics data (1997-2004) for the state of Florida were assembled and analyzed. Study Design. We used a pooled, cross-sectional design. Logistic regressions with time fixed-effects were estimated separately for the 12 most common ambulatory surgical procedures. Our quality outcomes were risk-adjusted 7-day and 30-day mortality and 7-day and 30-day unexpected hospitalizations. Risk-adjustment for patient demographic characteristics and severity of illness were calculated using the DCG/HCC methodology adjusting for primary diagnosis only and separately for all available diagnoses. Principal Findings. Although neither ASCs nor HOPDs performed better overall, we found some difference by procedure that varied based on the risk-adjustment approach used. Conclusions. There appear to be important variations in quality outcomes for certain procedures, which may be related to differences in organizational structure, processes, and strategies between ASCs and HOPDs. The study also confirms the importance of risk-adjustment for comorbidities when using administrative data, particularly for procedures that are sensitive to differences in severity.