Persistent sex disparity in liver transplantation rates.

Background: Studies have demonstrated that there are sex disparities in the rate of liver transplantation. However, little is known statistically about whether this disparity is caused by liver compartment size, Model for End-Stage Liver Disease adjustments, or regional differences.

Methods: We use retrospective data from the United Network for Organ Sharing Standard Treatment Analysis and Research data files for liver transplantation from 1995 through 2012. The final sample consists of 150,149 patients. These data contain information on all individuals who registered for the liver transplant waiting list as well as updated outcome data. Linear probability and logistic regression models were both used.

Results: Women were 4.8 percentage points less likely to receive a transplant. Adjustment for race, weight, body mass index, region, education, and other characteristics attenuated the sex difference by roughly 19% (from 4.8 to 3.9 percentage points). The disparity was consistent across the 11 United Network for Organ Sharing allocation regions. Comparing the heaviest women to the lightest men, the disparity flipped. Pairwise comparisons between men and women of various sizes suggest that disparities in favor of men increase with the ratio of male-to-female size.

Conclusion: Our results document persistent sex disparity in liver transplantation, only 19% of which is explained by size differentials between men and women. Differences in rates of transplantation are increasing in the ratio of male-to-female height and weight, suggesting that some of the disparity is explained by differences in liver compartment size.