High volume and outcome after liver resection: surgeon or center?

INTRODUCTION: In a case controlled analysis, we attempted to determine if the volume-survival benefit persists in liver resection (LR) after eliminating differences in background characteristics.
METHODS: Using the Nationwide Inpatient Sample (NIS), we identified all LR (n = 2,949) with available surgeon/hospital identifiers performed from 1998-2005. Propensity scoring adjusted for background characteristics. Volume cut-points were selected to create equal groups. A logistic regression for mortality was then performed with these matched groups.
RESULTS: At high volume (HV) hospitals, patients (n = 1423) were more often older, white, private insurance holders, elective admissions, carriers of a malignant diagnosis, and high income residents (p < 0.05). Propensity matching eliminated differences in background characteristics. Adjusted in-hospital mortality was significantly lower in the HV group (2.6% vs. 4.8%, p = 0.02). Logistic regression found that private insurance and elective admission type decreased mortality; preoperative comorbidity increased mortality. Only LR performed by HV surgeons at HV centers was independently associated with improved in-hospital mortality (HR, 0.43; 95% CI, 0.22-0.83).
CONCLUSIONS: A socioeconomic bias may exist at HV centers. When these factors are accounted for and adjusted, center volume does not appear to influence in-hospital mortality unless LR is performed by HV surgeons at HV centers.