The Caseload Requirement for Renal Transplantation

An analysis of German hospital quality assurance data from 2013–2021

The requirement of an annual minimum caseload is an important instrument for ensuring optimal kidney transplantation (KTx) outcomes. In Germany, the Federal Joint Committee (G-BA, Gemeinsamer Bundesausschuss) requires a minimum caseload of 25 KTx/year (1). This is based on a postulated causal relationship between quantity of services provided and quality of outcomes achieved (2). In actual fact, the evidence to support this assumption is mixed with regard to KTx (3, 4, 5). The aim of our study was to review the current cut-off value of 25 transplantations/year.

Methods

We analyzed quality reports of German hospitals, using the reimbursement.info tool, and activity reports of the centers from 2013–2021 published by the German Organ Transplantation Foundation (DSO, Deutsche Stiftung Organtransplantation). Length of hospital stay data were obtained from the nationwide German hospital billing database of the German Federal Statistical Office (Statistisches Bundesamt, Destatis). Available endpoints included perioperative complications (blood transfusion or revision surgery), immediate start of the graft function (maximum of one postoperative dialysis) and good graft quality at discharge from hospital (glomerular filtration rate [GFR] ≥ 20 mL/min). The number of KTx/year was calculated per center as the mean of the procedures performed annually during the period 2013–2021. We analyzed the outcomes with the cut-off value of 25 cases/year and examined potential alternatives in increments of 20 cases/year. The chi-square test was used for group comparisons. In addition, linear models with logistic link function and binomially distributed residuals were used in a generalized fashion, taking cluster effects into account, using an exchangeable covariance structure. As the analysis is not adjusted for multiple testing, statements on statistical significance should be understood as descriptive p-values.

Results

We analyzed 12 409 deceased-donor kidney transplantations and 5096 living-donor kidney transplantations (Tables 1 and 2). For the current cut-off value of 25 KTx/year, which was not reached 72 times across all center sizes, a difference in deceased-donor KTx complication rates in favor of smaller centers was noted. Centers with higher caseloads achieved better results with regard to immediate graft function. There was no difference with respect to good graft quality at discharge. In increments of 20 KTx/year, the lowest complication rate was reached at an annual caseload of ≤ 20 KTx. With regard to immediate graft function, centers with > 80 KTx achieved the best results. Centers with >80 KTx were found to have the highest rate of good graft quality at discharge. When using 25 KTx/year as the cut-off value, there were no differences in complication rates for living-donor KTx. The rate of immediate graft function was higher in centers with ≥ 25 KTx/year. There was no difference in the rate of good graft quality at discharge. For living-donor KTx, the lowest complication rate was achieved in centers with an annual caseload between 61 to 80 KTx. As for immediate graft function, centers with a high caseload of ≥ 80 KTx/year achieved the best outcomes. Centers with ≤ 20 KTx/year were found to have the highest rate of good graft quality at discharge.

Table 1

Perioperative complications, immediate graft function and good graft quality in relation to the minimum caseload requirement of 25 KTx/year

Table 2

Perioperative complications, immediate graft function and good graft quality in relation to performed KTx/year*

For deceased-donor and living-donor kidney transplantations, the mean rates of complete data sets were for perioperative complications 85% and 96%, for immediate graft function 87% and 76%, and for good graft quality 77% and 69%, respectively. The length of hospital stay was longer in centers with low caseloads (Table 2).

Discussion

Our results question the current minimum caseload regulation in Germany concerning KTx. With regard to deceased-donor KTx, organ selection based on stricter criteria could improve outcomes in centers with low caseloads. It is also conceivable that patients with higher disease severity are being treated at larger centers. Thus, one of the limitations of our data set is that it contains no information on patient characteristics and graft properties.

The difference in outcomes for the endpoint „good transplant quality (at discharge)” in low-volume centers could partially be due to the prolonged length of hospital stay. In these low-volume centers, kidney function after deceased-donor kidney transplantation is tested on average six days later compared to higher-volume centers. In centers with larger caseloads, a training-related effect and the splitting of the KTx between several surgeons could be of relevance. We assume that in centers where living-donor KTx is performed, only highly experienced surgeons usually perform living-donor KTx. This could be one reason why high-volume centers have achieved better outcomes with regard to immediate graft function.

The varying completeness of the data sets for the various caseload categories is a further limitation; the quality reports cite data protection requirements as the reason for this shortcoming. Given this incompleteness of the data, the results for living-donor KTx are only of limited use (in centers < 25 KTx/year, data completeness for immediate graft function is 49% and for good graft quality 52%). In addition, the quality criteria are defined in rather broad terms.

Overall, our results do not support the usefulness of a minimum caseload requirement for KTx. Instead, the quality assurance data collected should be closely monitored at center level and be a key factor in deciding whether or not a center is allowed to perform kidney transplantations. After all, even at best, a minimum caseload requirement can only be a surrogate parameter for quality. This value becomes obsolete as soon as quality itself is assessed in a binding manner.

Philipp Reimold, Cem Aksoy, Jonas Beckmann, Aristeidis Zacharis, Christer Groeben, Philipp Karschuck, Nicole Eisenmenger, Josef Geks, Rainer Koch, Luka Flegar, Johannes Huber

Department of Urology, Philipps University Marburg, Marburg, Germany (Reimold, Aksoy, Beckmann, Zacharis, Groeben, Karschuck, Koch, Flegar, Huber)

Reimbursement Institute, Hürth, Germany (Eisenmenger)

Department of General, Visceral and Vascular Surgery, Philipps University Marburg, Marburg, Germany (Geks)

Acknowledgement

This article is dedicated to Prof. Dr. med. Dr. h. c. Manfred Wirth (1949–2024). He was the academic teacher of the authors AZ, CG, PK, LF, and JH.

Conflict of interest statement
The authors declare no conflict of interest.

Manuscript received on 21 January 2024, revised version accepted on 26 sJune 2024

Translated from the original German by Ralf Thoene, M.D.

Cite this as:
Reimold P, Aksoy C, Beckmann J, Zacharis A, Groeben C, Karschuck P, Eisenmenger N, Geks J, Koch R, Flegar L, Huber J: The caseload requirement for renal transplantation—an analysis of German hospital quality assurance data from 2013–2021. Dtsch Arztebl Int 2024; 121: 746–7. DOI: 10.3238/arztebl.m2024.0139

References

1. Gesetze im Internet: § 136b SGB 5-Einzelnorm. www.gesetze-im-internet.de/sgb_5/__136b.html (last accessed on 16 November 2023).

2. Gemeinsamer Bundesausschuss: Mindestmengenregelungen. www.g-ba.de/richtlinien/5/ (last accessed on 16 November 2023).

3. Barbas AS, Dib MJ, Rege AS, et al.: The volume-outcome relationship in deceased donor kidney transplantation and implications for regionalization. Ann Surg 2018; 267: 1169–72

4. Hentschker C, Mennicken R, Reifferscheid AS, Thomas D, Wasem J, Wübker A: Der kausale Zusammenhang zwischen Zahl der Fälle und Behandlungsqualität in der Krankenhausversorgung. Essen: Rheinisch-Westfälisches Institut für Wirtschaftsforschung 2016.

5. Sonnenberg EM, Cohen JB, Hsu JY, et al.: Association of kidney transplant center volume with 3-year clinical outcomes. Am J Kidney Dis 2019; 74: 441–51