The system designed to fairly allocate donated livers in the United States has inadvertently disadvantaged women for more than two decades, according to medical research. A 2020 study found that women were 8.6 percent more likely than men to die waiting for a liver transplant and 14.4 percent less likely to receive a deceased donor liver transplant compared to men.
The disparity stems from the Model for End-Stage Liver Disease (MELD), a scoring system introduced in 2002 that ranks liver transplant candidates based on how urgently they need an organ. Introduced to replace a first-come, first-served allocation system, MELD calculates scores using blood test values including bilirubin, creatinine, and blood clotting time, with sodium levels considered in later refinements. Traditionally, scores range from 6 to 40, with higher scores indicating greater urgency.
The problem lies in how the system uses creatinine, a waste product produced by muscles during metabolism. Creatinine levels are used to assess kidney function since the kidneys filter and remove this compound from the bloodstream. Women typically have lower muscle mass than men, meaning a man and woman with identical kidney dysfunction will have different creatinine levels. The original MELD model did not account for this biological difference, causing women's scores to appear lower than their actual medical severity warranted, placing them farther down the waiting list.
Dr. Ray Kim, a transplant hepatologist at Mayo Clinic in Arizona who developed the original MELD system, introduced MELD 3.0 in 2023 to address these disparities. The new model adjusts women's scores upward by 1.33 points to account for differences in creatinine levels between the sexes. MELD 3.0 also measures an additional biomarker called albumin and adjusts for interactions between variables to improve accuracy for all patients.
Despite these changes, early research on MELD 3.0's effectiveness has produced sobering findings. The new system has not yet brought men and women to parity on the liver waitlist, according to preliminary data cited in available reports. Researchers have begun questioning whether the focus on creatinine adjustment addresses the root causes of the disparity or whether other factors in the allocation system may be contributing to unequal access.
The significance of achieving gender parity in liver transplant allocation extends beyond statistical equity. Liver disease affects both men and women, and the ability to access transplants can mean the difference between life and death. The fact that a system explicitly designed for equitable allocation inadvertently disadvantaged women for over two decades underscores how bias can be embedded in medical algorithms even when designers intend fairness.
The findings raise broader questions about how medical scoring systems are designed and evaluated. As healthcare increasingly relies on algorithms to allocate scarce resources, the MELD experience demonstrates the importance of examining how biological differences between populations are—or are not—factored into those models.
