To the Editor:
In their careful analysis, Khuri et al 1 found no association between hospital procedural volume and 30-day mortality with eight common operations in the VA Health System. Their findings contrast sharply with consistently strong volume/outcome associations described in the private sector over the past two decades. In explaining the discrepancy, the authors suggest that volume/outcome relationships described in previous studies, based predominantly on administrative data, could be attributable to inadequate case-mix adjustment.
Their own prospective clinical data, however, suggest that case-mix adjustment in volume/outcome analysis may not be important after all. As in most previous studies, the authors found no systematic differences in patient age, illness severity, or other risk factors between high- and low-volume providers in the VA. Under these conditions, adjusted and unadjusted analysis of volume/outcome relationships will produce the same results.
Instead, the lack of an association between hospital procedural volume and mortality in the VA may reflect structural and organizational factors unique to the VA system. Compared to low-volume hospitals in the private sector, low-volume VA hospitals may “overperform” because their staffs often include high-volume surgeons from university affiliates. Conversely, high-volume VA hospitals may “underperform” relative to their private sector counterparts; for example, VA hospitals lack market incentives that encourage surgeons to develop clinical niches and specialized expertise. In addition, surgical residents may be providing a relatively large proportion of care in VA hospitals.
The work by Dr. Khuri and the NSQIP suggests that there may be little to gain from regionalizing surgery within the VA. For the remaining 98% of patients undergoing high-risk surgery in the private sector, however, policies concentrating selected procedures in high-volume centers could potentially save thousands of lives each year. 2
October 28, 1999
John D. Birkmeyer MD
References
- 1.Khuri SF, Daley J, Henderson W, et al. Relation of surgical volume to outcome in eight common operations: results from the VA National Quality Improvement Program. Ann Surg 1999; 230: 414–432. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Birkmeyer JD. Should we regionalize major surgery? Potential benefits and policy considerations. J Am Coll Surg [in press]. [DOI] [PubMed]