L. H. Nicholas1, S. Stith2 1Johns Hopkins University School Of Medicine,Surgery,Baltimore, MD, USA 2University Of New Mexico,Albequerque, NM, USA
Introduction: A pervasive viewpoint in healthcare is that higher patient volume leads to better outcomes, implying that facility volume can be used to identify high-quality hospitals. Hundreds of studies documenting a positive correlation between hospital volume and patient outcomes (better outcomes at higher volume hospitals) have motivated the use of arbitrary minimum volume standards for elective surgical procedures. There is considerable variation across minimum volume standards used by the Centers for Medicare and Medicaid Services and commercial insurers when contracting with organ transplant centers. It is unknown whether some payers are relying on excessively high standards or whether payers are using thresholds that are too small.
Methods: We used data from the Scientific Registry of Transplant Recipients including all adult heart (54,874 patients in 191 transplant centers) and lung (25,128 patients in 103 transplant centers) transplants in the United States from October 1987 – December 2012 to assess whether transplant outcomes including 1-year mortality and 1-year graft failure vary across centers above and below the minimum volume standards. To account for potential confounding between unobserved patient characteristics and transplant center volume, we used an instrumental variables approach to predict volume of a patient's center with the volume of the center closest to a patient's home zip code.
Results: Minimum volume thresholds affect many transplant centers. Only 57% of kidney transplant centers, 71% of liver, 44% of heart, and 61% of lung transplant centers ever meet the highest minimum volume requirement during our study period. We failed to find a significant relationship between transplant center volume and patient outcomes for either patient or graft survival for any of the four organs studied.
Conclusion: Despite good intentions, minimum volume standards currently used by public and private payers are not identifying higher quality transplant centers and may create unnecessary barriers for patients who could be served by smaller, closer centers.