The matching and offer process not only uses patient and donor data to determine physical and immunogenic compatibility, but also assesses recipient priority based on medical urgency as well as utility, which is sometimes measured as the number of years gained for the patient through the transplant. While a very elderly patient may have high medical urgency, they may be less able to utilize the kidney of a young patient which may last 20 plus years.
These questions are ethically complex and also have a strong equity element. Ongoing negotiation of scoring variables that prioritize some patients will necessarily exclude others.
For example, Pediatric End-Stage Liver Disease (PELD) score is used to determine the degree of liver dysfunction in pediatric patients and therefore medical urgency. This in turn influences allocation and scoring. Because the complications of liver disease make patients sicker than the actual liver function and PELD score might indicate (e.g., infections, growth failure, other complications), patients can request exception points (or, in some jurisdictions, exemptions) that result in higher medical urgency to make things more equitable. However, we know that non-white patients request exception points at a lower frequency than white patients do.
Another example is the effect scoring pre-dialysis waiting time points for kidney patients. This waiting time was originally supposed to support equity. But in the US, getting on the transplant list as soon as possible in the progression of kidney disease can allow for unlimited pre-dialysis “waiting time” points to accumulate because there is no cap. This advantages demographics more likely to have private insurance, get diagnoses sooner, and join the wait list before receiving dialysis.
Some fixes related to how candidates are prioritized are simpler problems that require better measurements. Women waiting for liver transplants are more likely to die on the waitlist likely due to creatine measures underestimating kidney function in women, an issue further exacerbated by serum sodium level calculations. These differences can be addressed by laboratory, policy and algorithm changes that measure and score these parameters more accurately.
While attempts are made to predict such impacts through the process of improving policies, it is not always possible to do so quickly and effectively.
Source: (National Research Council. 2022. Realizing the Promise of Equity in the Organ Transplantation System. Washington, DC: The National Academies Press. https://doi.org/10.17226/26364)