Association of Kidney Transplant Center Volume With 3-Year Clinical Outcomes

Rationale & Objective A robust relationship between procedure volume and clinical outcomes has been demonstrated across many surgical fields. This study assessed whether a center volume–outcome relationship exists for contemporary kidney transplantation, specifically for diabetic recipients, older recipients (aged ≥65 years), and recipients of high kidney donor profile index (KDPI ≥ 85) kidneys. Study Design Retrospective cohort study. Setting & Participants Adult kidney-only transplant recipients who underwent transplantation between 2009 and 2013 (N = 79,581). Exposures The primary exposure variable was center volume, categorized into quartiles based on the total kidney transplantation volume. Quartile 1 (Q1) centers performed a mean of fewer than 66 kidney transplantations per year, whereas Q4 centers performed a mean of more than 196 kidney transplantations per year. Outcomes All-cause graft failure and mortality within 3 years of transplantation. Analytical Approach Multivariable Cox frailty models were used to adjust for donor characteristics, recipient characteristics, and cold ischemia time. Results Minor differences in rates of 3-year deceased donor all-cause graft failure across quartiles of center volume were observed (14.9% for Q1 vs 16.7% for Q4), including in subgroups (diabetic recipients, 18.4% for Q1 vs 19.7% for Q4; older recipients, 19.4% for Q1 vs 22.5% for Q4; recipients of high KDPI kidneys, 26.5% for Q1 vs 26.5% for Q4). Results were similar for 3-year mortality. After adjustment for donor, recipient, and graft characteristics using Cox regression, center volume was not significantly associated with all-cause graft failure or mortality within 3 years, except that diabetic recipients at Q3 centers had slightly lower mortality (compared with Q1 centers, adjusted HR of 0.85 [95% CI, 0.73-0.99]). Limitations Potential unmeasured confounding from patient comorbid conditions and organ selection. Conclusions These findings provide little evidence that care in higher volume centers is associated with better adjusted outcomes for kidney transplant recipients, even in populations anticipated to be at increased risk for graft failure or death.