In the US liver allocation system, nonstandardized model for end-stage liver disease (MELD) exceptions (NSEs) increase the waitlist priority of candidates whose MELD scores are felt to underestimate their true medical urgency. We determined whether NSEs accurately depict pretransplant mortality risk by performing mixed-effects Cox proportional hazards models and estimating concordance indices. We also studied the change in frequency of NSEs after the National Liver Review Board’s implementation in May 2019. Between June 2016 and April 2022, 60,322 adult candidates were listed, of whom 10,280 (17.0%) received an NSE at least once. The mean allocation MELD was 23.9, an increase of 12.0 points from the mean laboratory MELD of 11.9 (P < .001). A 1-point increase in allocation MELD score due to an NSE was associated with, on average, a 2% reduction in hazard of pretransplant death (cause-specific hazard ratio: 0.98; 95% CI: 0.96, 1.00; P = .02) compared with those with the same laboratory MELD. Laboratory MELD was more accurate than allocation MELD with NSEs in rank-ordering candidates (c-index: 0.889 vs 0.857). The proportion of candidates with NSEs decreased significantly after the National Liver Review Board from 21.5% to 12.8% (P < .001). NSEs substantially increase the waitlist priority of candidates with objectively low medical urgency.

中文翻译：

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终末期肝病评分异常的非标准化模型与成人肝移植候选者候补名单死亡率的关联


在美国肝脏分配系统中，终末期肝病非标准化模型 （MELD） 例外 （NSE） 增加了 MELD 评分被认为低估了其真实医疗紧迫性的候选人的候补名单优先级。我们通过执行混合效应 Cox 比例风险模型和估计一致性指数来确定 NSE 是否准确描述移植前死亡风险。我们还研究了 2019 年 5 月国家肝脏审查委员会实施后 NSE 频率的变化。2016 年 6 月至 2022 年 4 月期间，列出了 60,322 名成年候选人，其中 10,280 名 （17.0%） 至少获得了一次 NSE。平均分配 MELD 为 23.9，比平均实验室 MELD 11.9 增加 12.0 分 （P < .001）。由于 NSE 导致的分配 MELD 评分增加 1 分与移植前死亡风险降低 2% 平均相关（原因特异性风险比：0.98;95% CI：0.96,1.00;P = .02） 与具有相同实验室 MELD 的受试者相比。在对候选者进行排名排序方面，实验室 MELD 比带有 NSE 的分配 MELD 更准确 （c-index： 0.889 vs 0.857）。在美国国家肝脏审查委员会之后，具有 NSE 的候选人比例从 21.5% 显着下降到 12.8% （P < .001）。NSE 大大提高了客观上医疗紧急程度较低的候选人的候补名单优先级。