BACKGROUND: Status 1A patients are prioritized over liver disease patients regardless of model for end-stage liver disease (MELD) score. We aimed to identify groups with high waitlist mortality in Status 1A and MELD\u3e/=40 patients to determine who would most benefit from transplantation. METHODS: Data on patients listed as Status 1A (n=4447) and MELD\u3e/=40 (n=3663) over 15 years (2002 to 2017) obtained from UNOS/OPTN registry. They were divided into two; derivation and validation groups. Risk factors associated with 28-day waitlist mortality were identified in derivation group and provided risk scores to divide patients into risk groups. Score system was applied to validation group to check its applicability. RESULTS: Risk factors for waitlist mortality in Status 1A included life support, performance status, severe coagulopathy, severe hypo or hypernatremia, and grade 3-4 encephalopathy. Risk factors in MELD\u3e/=40 included higher MELD scores (\u3e/=45), age, sex, race, life support, and encephalopathy. On comparing 7-day and 28-day mortality, both were higher in Status 1A and MELD\u3e/=40 high-risk groups compared to low-risk groups in the derivation group (p\u3c0.001). Probability of transplantation was lowest for high-risk MELD\u3e/=40 patients compared to all other groups (p\u3c0.001). These findings were reproduced in the validation set. Our proposed risk stratification system also showed acceptable 1 year graft and patient survival in high-risk groups. CONCLUSIONS: Our risk scoring system for extremely ill liver transplant candidates successfully stratified risk of waitlist mortality. Waitlist outcomes might be improved by modifications involving categorization of patients based on presence/absence of risk factors
