2007年11月20日 Archives of Surgery 11月的一项研究报告指出，肝移植等待名单上的患者死亡率在经历了短暂的上升之后，新的终末期肝病模型（MELD）评分标准使得等待期死亡率有所下降，同时也使患者等待新肝脏的时间有所缩短。
美国田纳西州范德比尔特大学医学中心的Mary T. Austin博士和他的同事们写到，“在1999年，医学会（IOM）认为等待时间不是医疗紧急程度的指标，而移植率、病情严重程度和等待期死亡率才更加重要。IOM建议，尸体捐肝者的肝脏分配可以通过建立某种机制得到改进，这种机制倾向于病情的严重程度，不再强调患者的等待时间……”。而MELD则被认为能够满足以上要求。
在1999年3月1日至2004年7月30日期间美国器官资源共享网络（UNOS）的移植数据的基础上，研究人员对肝移植等待者中的所有成年人进行了研究。该研究的目的在于等待期的死亡率、从等待到进行移植手术的时间、新注册等待移植的患者数目、移植术后的生存期等。
研究者表示，在经历了最初的上升之后，等待期死亡率和等待时间都有所下降，这种变化与MELD的分配政策有关。
“随着从‘强调等待时间’的分配政策，到‘倾向于病情严重程度、不再强调患者的等待时间’分配政策的过渡，等候名单上很多病情不严重、仅为了增加等待时间的患者将被除名，因此，名单上剩余患者从等待到接受移植的时间也就整体缩短了。”
最后，研究人员总结说：“在实体器官移植中，肝脏移植是第一个以客观评分为基础的器官分配政策。仔细评估尸体捐赠者肝脏分配政策的主要变化是至关重要的，因为这些变化可能指引着将来分配政策的发展方向……”从某种程度上来说，美国卫生资源和服务管理局支持这项工作，但文章作者透露没有任何相关的财政支持。
来自美国马里兰大学的Benjamin Philosophe博士和Stephen T. Bartlett医生在评论文章中指出，“MELD对生存期的影响仍然存在争议......MELD评分系统对终末期肝病总体负担的影响并不能得到充分的评估。长期的公开评论促使了MELD评分系统的实施；因此，肝脏移植中心有很长的时间对政策的变化做出反应。通过这些数据不能得到充分评估的范围包括以下几点：政策的变化是否会对移植中心等待名单的实施产生影响、对终末期肝病所有患者的死亡率和疗效的影响，包括不在移植等候名单上的终末期肝病患者。
New MELD Liver Transplant Criteria Have Decreased Waiting List Death Rate
November 20, 2007 — After a temporary increase in death rate among those on the waiting list, the new Model for End-Stage Liver Disease (MELD) criteria for allocating livers for transplant have decreased the waiting list mortality rate as well as the amount of time patients spend waiting for a new liver, according to a study reported in the November issue of the Archives of Surgery.
"In 1999, the Institute of Medicine（IOM）deemed that waiting time was a poor indicator of medical urgency and that rates of transplantation, illness severity, and waiting list mortality were much more meaningful," write Mary T. Austin, MD, MPH, from Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues.
"The IOM recommended that allocation of deceased donor livers could be improved by instituting a mechanism that favored disease severity and deemphasized patient waiting time.... The [MELD] was identified as potentially meeting these requirements.
The objective of this study was to assess the effect of MELD on waiting list mortality, using an interrupted time series design with a nominal inception point of the intervention (implementation of the MELD policy) on February 27, 2002.
Using the United Network for Organ Sharing Standard Transplant Analysis and Research database from March 1, 1999, to July 30, 2004, the investigators studied all adult candidates on the waiting list for liver transplantation in the United States.
The primary endpoints were mortality while on the waiting list, waiting time to transplantation, number of new registrants, and survival after transplantation.
Before implementation of MELD, no trend was identified. However, after the intervention, there was an immediate effect of increasing waiting list mortality by 2.2 deaths per 1000 registrants per month (from approximately 11 to 13 deaths per 1000 registrants per month; 95% confidence interval [CI], 1.1 – 3.4; P = .001). Subsequently, waiting list mortality decreased over time ( 0.09 death per 1000 registrants per month; 95% CI, 0.16 to 0.03; P < .001). There was also an immediate effect of decreased waiting time (from approximately 294 to 250 days; 44.4 days; 95% CI, 77.1 to 11.7 days; P < .001), which stabilized to a lower postintervention steady state.
The number of new registrants listed per month and 3- and 6-month posttransplantation survival were not affected by the MELD policy change.
"After an initial increase in waiting list mortality, the implementation of the MELD-based allocation policy was associated with an overall decline in waiting list mortality and time to transplantation," the study authors write.
"With the transition in allocation policy from a system that emphasized waiting time to one that favored disease severity with a de-emphasis on patient waiting time, many less-ill registrants placed on the list for the sole purpose of 'banking time' may have been removed, leading to an overall decrease in the time to transplantation for the remaining registrants."
"In solid-organ transplantation, the liver transplantation community was the first to adopt an objective score as the basis of organ allocation policy," the study authors conclude.
"Careful evaluation of this major change in the allocation of deceased donor livers is essential because it may direct future allocation policies.... Because significant resources are expended in efforts to equitably allocate organs, this work provides empiric justification of this policy change."
The Health Resources and Services Administration supported this work in part. The authors have disclosed no relevant financial relationships.
In an invited critique, Benjamin Philosophe, MD, PhD, and Stephen T. Bartlett, MD, from the University of Maryland in Baltimore, note that the effect of MELD on survival remains controversial.
"The impact of the MELD scoring system on total burden of end-stage liver disease cannot be fully assessed by the study," Dr. Philosophe and Dr. Bartlett write."A long period of public comment preceded the implementation of the MELD scoring system; therefore, liver transplantation centers had a long lead time to react to the policy change. What cannot be fully assessed by these data are whether the policy change affected listing practices of transplantation centers and the effect on mortality and outcome for all patients with end-stage liver disease, including those who were not on transplantation waiting lists."
Arch Surg. 2007;142(11):1079–1085.
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