MELD score disadvantages women on the liver transplant waiting list

Last Updated: 2020-05-28

By Marilynn Larkin

NEW YORK (Reuters Health) - The Model for End-stage Liver Disease (MELD) organ allocation system has led to sex disparities, with women less likely to receive a deceased donor liver transplant (DDLT) and more likely to die on the waiting list, researchers say.

"MELD was developed to be an unbiased measure to assess disease severity and ensure the sickest patients receive the highest priority for transplant," Dr. Jayme Locke of the University of Alabama at Birmingham told Reuters Health by email. "However, MELD as a measure of disease severity is biased against women."

"Multiple studies have demonstrated that serum creatine (sCr) overestimates renal function in women compared to men such that women with the same (glomerular filtration rate) as men have a lower sCr and...lower calculated MELD scores, and therefore lower priority for transplant," she said. "Sex-based differences in sCr generation are not accounted for by MELD, suggesting MELD may not accurately prioritize the sickest patients for transplantation."

"Women at the top of the priority list are more likely than men to have livers declined, with donor-recipient size mismatch reported four times more often among women than men," she noted. "Women with at least one decline are 26% more likely than men to die."

"Although more common among women, small stature is not unique to one biologic sex or the other," she added. "Despite this, studies have demonstrated that even compared to small men, small women have 1.2-fold higher odds of having a liver declined for donor-recipient size mismatch."

Dr. Locke and colleagues studied adult liver-only transplant listings reported to the Organ Procurement and Transplantation Network from June 2013 to March 2018.

As reported in JAMA Surgery, among 81,357 wait-listed adults (mean age, about 55), 36.1% were women. After weighting for United Network for Organ Sharing (UNOS) region, as Dr. Locke noted, women were 8.6% more likely than men to die while on the waiting list (adjusted hazard ratio, 1.11) and 14.4% less likely to receive a DDLT (aHR, 0.86).

With regard to geography, organ procurement organization was the only variable that was significantly associated with increased disparity between female sex and wait-list mortality (22.1% increase), whereas no measure was associated with DDLT.

The allocation MELD score was associated with a 53% increase in the disparity between the sexes, such that women had a 14.4% greater risk of wait-list mortality than men (aHR, 1.14); when weighted by sCr level, the aHR was 1.13, representing a 35.5% increase in the disparity versus the unweighted model.

A candidate's body size - e.g., weight, height, circumference, body mass index - and liver measurements had the strongest association with disparities in wait-list mortality (corresponding to a 125.8% increase in risk of death on the waiting list among women compared with men) and DDLT (49% increase).

Dr. Locke said, "These data suggest implicit bias may be at play, and further motivate the need to incorporate an objective, unbiased metric for optimizing donor-recipient size matching into our existing MELD-based allocation system."

Dr. Elizabeth Verna of Columbia University Irving Medical Center in New York City, coauthor of a related editorial, commented in an email to Reuters Health, "Ultimately the U.S. Secretary for Health and Human Services has authority to mandate that UNOS... address these issues."

"However, I think it is important to note that part of the reason these changes have not occurred is that we do not have an accurate measure of kidney function in the setting of extremes of muscle mass (e.g., men vs. women; end-stage liver disease vs. general population)," she said. "We also do not have an accurate/reliable way to measure size that fits reasonably within the constraints of deceased donation."

"Given this, what may prove most helpful would be for the Secretary for HHS to encourage scientists to pursue this line of research and for the National Institutes of Health to fund these types of studies," she concluded.

SOURCE: https://bit.ly/2TNHTQN, https://bit.ly/2Bc8CzW and https://bit.ly/2TNmWoZ JAMA Surgery, online May 20, 2020.