A Data-Driven Approach to Defining the Volume-Outcome Relationship in Renal Transplantation

E. L. Godfrey¹, M. D. Bailey¹, W. C. Frankel¹, A. Rana²

¹Baylor College of Medicine, Houston, TX, ²Division of Abdominal Transplantation, Department of Surgery, Baylor College of Medicine, Houston, TX

Meeting: 2020 American Transplant Congress

Abstract number: B-224

Keywords: Graft survival, Kidney transplantation, Outcome, Resource utilization

Session Information

Session Name: Poster Session B: Non-Organ Specific: Disparities to Outcome and Access to Healthcare

Session Type: Poster Session

Date: Saturday, May 30, 2020

Session Time: 3:15pm-4:00pm

Presentation Time: 3:30pm-4:00pm

Location: Virtual

*Purpose: Advances in immunosuppression and management continually improve short- and long-term outcomes of renal transplantation. However, center volume and expertise, while commonly believed to affect outcomes, is inconsistently linked to improved endpoint measures, and there is no standardized definition of high-volume and low-volume centers or how their behaviors differ. The aim of the present study is to identify meaningful, data-driven volume thresholds predicting improved outcomes for renal transplant centers.

*Methods: All sole KTx cases performed on patients over the age of 18 between 2003 and 2015 in the United Network for Organ Sharing (UNOS) database were reviewed. Patients listed for or receiving other organs and transplants were excluded. A small number (under 1%) of patients were excluded due to lack of follow-up data. Stratum-specific likelihood ratios (SSLR) were calculated to establish volume thresholds predictive of the primary outcome of 1 year graft loss. Demographic and outcomes data were compared between volume strata and significance tested using chi-squared tests or analysis of variance (ANOVA) and post-hoc Tukey’s.

*Results: A total of 220,006 recipients were included in the final cohort, 184,685 of which were included in threshold-finding. Four distinct volume strata predicting graft failure within one year were identified by SSLR calculation and confidence interval analysis: very low (under 10), low (10-60), intermediate (60-164) and high volume (over 164 transplants/year). As volume increases, outcomes improve including decreasing 1-year mortality (4.5% for very low vs 2.8% for high, p<0.0001) and decreasing length of stay (8.3 days for very low vs 6.6 days for high, p<0.0001). The majority of transplants are performed at intermediate and high volume centers, which utilize older donors with overall higher KDPIs and a longer average wait time . Very low volume centers have markedly inferior outcomes (SSLR of 2.7 for graft loss against centers overall) despite favorable PRAs and KDPIs and short wait times; these lowest volume centers serve relatively more non-white recipients (62% vs 50% for high and intermediate, p<0.0001) but account for only 1.1% of total renal transplants.

*Conclusions: This study adds to the existing literature by estimating data-driven thresholds for annual renal transplant volumes at which meaningful differences in graft survival, length of stay, and mortality can be observed and highlight the gap in outcomes between very low volume centers and all others.

Details of patients undergoing renal transplantation (KTx) stratified by center volume
	Very low volume (<10KTx/year, 69 centers) n=2,430	Low volume (10-60 KTx/year, 108 centers) n=54,349	Intermediate volume(60—164 KTx/year, 75 centers)n=103,175	High volume (>164 LTx/year, 20 centers) n=60,052	P value
SSLR (95% CI)	2.70 (2.28, 3.20)	1.07 (1.02, 1.12)	0.99 (0.96, 1.02)	0.89 (0.86, 0.95)
Time on wait list (days)	549.7 ± 575	709.6 ± 692.9	725.5 ± 703.2	754.5 ± 782.9	<0.0001
Peak PRA	13.2 ± 26.8	15.1 ± 28.9	17.1 ± 29.9	14.6 ± 27.8	<0.0001
Average center KDPI	0.42 ± 0.27	0.46 ± 0.27	0.48 ± 0.27	0.51 ± 0.27	<0.0001
LOS (days)	8.3 ± 6.7	7.5 ± 10.0	6.6 ± 9.0	6.6 ± 15.2	<0.0001
1-year mortality	109 (4.5%)	1,910 (3.5%)	2,949 (2.9%)	1,669 (2.8%)	<0.0001
Graft loss within first year	114 (4.7%)	2,061 (3.8%)	3,794 (3.7%)	2,048 (3.4%)	0.00012

To cite this abstract in AMA style:

Godfrey EL, Bailey MD, Frankel WC, Rana A. A Data-Driven Approach to Defining the Volume-Outcome Relationship in Renal Transplantation [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/a-data-driven-approach-to-defining-the-volume-outcome-relationship-in-renal-transplantation/. Accessed May 31, 2025.

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