The center effect: is bigger better?

Grouping US kidney transplant centers according to the number of transplants performed during the past 10 years into those that reported more than 1,000 transplants and all others showed: 1. Ten-year graft survival rates at larger centers were no more than 5% higher than those at other centers. 2. Graft survival rates were most similar between the 2 center groups when the donor was an HLA-identical sibling or when the recipient had chronic glomerulonephritis. 3. Larger centers had a slightly but noticeably higher graft survival rate when the patient had juvenile onset diabetes, when the donor was older than age 60 and when the donor was a spouse. 4. Most differences in graft survival rates between larger and all other centers were apparent only 2-3 years after transplantation, suggesting that the differences reflect long-term management of the patients or that an historical difference existed that has disappeared in recent years.