The relationship between center volume and patient outcomes has been validated across multiple complex surgical procedures. In this volume of Transplantation, Alqahtani et al1 present their analysis of the SRTR data set between 2007 and 2018 with regards to center volume and surgical outcomes following liver transplantation. Here, they show that patients listed at low-volume centers (ie, <20 liver transplants annually) are less likely to receive a liver transplant and have a higher risk of post-liver transplant mortality than patients transplanted at high-volume centers. Patients listed at low-volume centers were also more likely to be transferred to another center or removed from the waitlist.
Do these data mean that we should avoid performing liver transplants at low-volume centers entirely? One needs to evaluate the source of some of these disparities to answer this question. Transplantation is one the most heavily regulated and scrutinized medical specialities in the United States, with outcomes examined by both the Center for Medicare Services (CMS) and the Organ Procurement and Transplantation Network (OPTN). To maintain public and patient safety and to maintain the ethical principles surrounding the selfless act of organ donation, the National Organ Transplant Act established the principle for solid organ transplant regulation by the federal government in 1984. Under the National Organ Transplant Act, center-specific transplant candidate and recipient outcomes are federally regulated, rigorously analyzed, and reported to a variety of audiences, including regulatory agencies, insurance companies, and the public. The “Final Rule,” enacted by the US Department of Health and Human Services in March 2000, dictated fair and ethical organ allocation and established oversight of transplant outcomes by the OPTN.2 The “Final Rule” requires preferential transplantation of the sickest candidates first while avoiding liver transplant futility, as well as mandating geographic parity. The hope was to shift away from the lack of standard medical criteria for recipient selection, which was felt to contribute to observed significant geographic disparities in allocation.
Oversight was further expanded in 2007 when CMS implemented conditions of participation (CoP) mandating extensive additional regulation of transplant outcomes. The goals of most of these statutes, as well as of the recently implemented acuity circles model,3 has been the establishment of a fair and equitable national allocation system that avoids wasting of organs based on objective medical criteria. Ideally, this would result in unbiased access and treatment of transplant patients, irrespective of geographic location. Sadly, instead of improving organ utilization of decreasing futility, the increased regulatory measures had the unintended consequences of decreasing center volume and increasing discards as programs became more risk averse.4 In response to an executive order to reduce regulatory costs, as well as advocacy by the American Society of Transplant Surgeons, in September of 2019, the duplicate CMS regulatory requirements for program recertification were removed. This somewhat loosened regulatory constraints on transplant programs. In the context of the present article, the analysis period spanned 2007 to 2018, before the implementation of these changes. This period was arguably the most stringent for regulatory oversight in transplantation. The adverse consequences of this regulation have been previously characterized and likely significantly impacted the outcomes reported here with respect to center size.
The current allocation criteria utilizing MELD or MELD-Na is explicitly designed to reduce the likelihood of patients dying while waiting for a liver, rather than choosing those patients most likely to have the best posttransplant survival. Based on the “Final Rule,” the current transplantation policy seeks to reduce short-term risk of death (ie, waitlist mortality) over long-term posttransplant survival.5 In complete contrast to these principles of organ allocation, CMS and OPTN metrics for transplant programs’ performance are principally based on posttransplant graft and patient survival. In 2007, the CoP issued by CMS required a minimum risk-adjusted posttransplant graft and patient survival rate for CMS certification and insurance reimbursement.6 The CoP criteria are contingent on 2 metrics: risk-adjusted 1-y posttransplant patient survival and 1-y graft survival,7 and waitlist outcomes do not feature on the assessments. With these regulations in mind, low-volume transplant centers are often less willing to take on transplant of high risk recipients or to accept marginal liver offers.8 This may impact the finding by the authors that patients listed at low-volume transplant centers are less likely to receive a liver and more likely to be transferred to another center or be removed from the waitlist.1 When the denominator is small, low-volume centers cannot afford poor outcomes, as a single adverse outcome could trigger the threshold for Membership and Professional Standards Committee review.
The authors further identify age, race, ethnicity, education, and socioeconomic status as independent risk factors for liver transplant outcomes. These social determinants of health are established risk factors in listing, waitlist mortality, and posttransplant survival.9 Unfortunately, they are also inadequately accounted for in the risk-adjusted outcomes scores utilized for measuring transplant center performance. As a result, already disadvantaged groups may be disproportionately affected by risk-averse transplant centers not willing to absorb such risk.8 We agree with the authors’ contention that this important issue warrants further in-depth evaluation.
Particularly applicable to the US healthcare system with its lack of a single payer, access to liver transplant is further affected by insurance coverage. This article demonstrates that patients with Medicare or Medicaid coverage have poorer waitlist and transplant outcomes, even after adjustment for clinicodemographic confounders.1 Access to liver transplantation requires both adequate insurance and financial means to cover the transplant, related hospitalization, and necessary immunosuppression. While provisions under the Affordable Care Act provided a mechanism for universal coverage in the United States, the adoption, timing of implementation, and level of coverage by these programs is state specific and has been variable. Some “Marketplace Plans” notoriously under-cover participants and institute unnecessary barriers to healthcare access. Insurance limits plan-approved transplant centers, which may increase the distance required to travel for transplantation.10 In addition, insurance plans may dictate covered conditions, timing, and medications available for treatment of liver disease, all of which may alter pretransplant and posttransplant mortality. For example, many state Medicaid programs mandate 6 mo of sobriety before transplant,11 despite evidence suggesting that early liver transplant in alcoholic liver disease improves survival.12 In addition, availability of Medicaid coverage for direct- acting antivirals improves pretransplant mortality in HCV patients.13
Finally, a major impetus of the recently implemented Acuity Circles allocation system has been the normalization of the geographic disparities in liver transplantation. The data from this article predates the recently adopted allocation changes, but it suggests geographic disparities may extend beyond regional borders. Risk-averse behavior may be encouraging low-volume centers to refer high risk patients to nearby high-volume centers, which could explain the finding by the authors that low- and medium- volume centers situated close to high-volume centers have lower posttransplant mortality.1 The geographic disparity also favored patients in smaller metropolitan areas, suggesting an impact of supply and demand for patients in more densely populated areas. Whether the newly implemented liver allocation policies will improve geographic access for waitlisted candidates remains to be seen.
Although the data show lower posttransplant mortality in high-volume centers when analyzed as a whole, closer analysis of the temporal trend relationship between center volume and patient outcomes for liver transplantation demonstrates that the difference has become less pronounced over time.14 Furthermore, the unintended consequences of transplant over-regulation likely skewed transplant center behavior, especially in low-volume centers. Such volume-based disparities may persist following the recent changes to both allocation and regulation, but these considerations suggest that the use of procedure volume as a sole marker of liver transplant center quality may not be entirely justifiable. Appropriate measures to define center quality should focus on both pretransplant and posttransplant outcomes, with robust risk adjustment strategies to encourage growth and innovation in this field,8 rather than to suppress it through excessive oversight.
1. Alqahtani SA, Stepanova M, Kabbara KW, et al. Liver transplant center size and the impact on the clinical outcomes and resource utilization. Transplantation. [Epub ahead of print. August 5, 2021]. doi:10.1097/TP.0000000000003915
2. Batra RK, Mulligan DC. Current status: meeting the regulatory goals of your liver transplant program. Curr Opin Organ Transplant. 2021;26:146–151.
3. Organ Procurement and Transplantation Network. OPTN Policy Notice: Liver and Intestine Distribution Using Distance From Donor Hospital. 2020.
4. White SL, Zinsser DM, Paul M, et al. Patient selection and volume in the era surrounding implementation of Medicare conditions of participation for transplant programs. Health Serv Res. 2015;50:330–350.
5. Schaubel DE, Guidinger MK, Biggins SW, et al. Survival benefit-based deceased-donor liver allocation. Am J Transplant. 2009;9:970–981.
6. Centers for Medicare & Medicaid Services. Medicare program; hospital conditions of participation: requirements for approval and re-approval of transplant centers to perform organ transplants. Fed Reg. 2007;72:15197–15280.
7. Axelrod DA. Balancing accountable care with risk aversion: transplantation as a model. Am J Transplant. 2013;13:7–8.
8. Adler JT, Axelrod DA. Regulations’ impact on donor and recipient selection for liver transplantation: how should outcomes be measured and MELD exception scores be considered? AMA J Ethics. 2016;18:133–142.
9. Rosenblatt R, Lee H, Liapakis A, et al. Equitable access to liver transplant: bridging the gaps in the social determinants of health. Hepatology. [Epub ahead of print. June 1, 2021]. doi:10.1002/hep.31986
10. Cicalese L, Shirafkan A, Jennings K, et al. Increased risk of death for patients on the waitlist for liver transplant residing at greater distance from specialized liver transplant centers in the United States. Transplantation. 2016;100:2146–2152.
11. Zhu J, Chen P-Y, Frankel M, et al. Contemporary policies regarding alcohol and marijuana use among liver transplant programs in the United States. Transplantation. 2018;102:433–439.
12. Mathurin P, Moreno C, Samuel D, et al. Early liver transplantation for severe alcoholic hepatitis. N Engl J Med. 2011;365:1790–1800.
13. Wahid NA, Lee J, Kaplan A, et al. Medicaid expansion association with end-stage liver disease mortality depends on leniency of Medicaid hepatitis C virus coverage. Liver Transpl. [Epub ahead of print. June 12, 2021]. doi:10.1002/lt.26209
14. Tracy ET, Bennett KM, Aviki EM, et al. Temporal trends in liver transplant centre volume in the USA. HPB (Oxford). 2009;11:414–421.