Why the new system for organ allocation is an improvement

My thoughts on the new framework for prioritizing lung transplant candidates

Samuel Kirton avatar

by Samuel Kirton |

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On Tuesday, Sept. 15, 2020, I received an email asking if I would participate in an exercise on how deceased donor organs are allocated. The opening statement read:

“The Organ Procurement and Transplantation Network [OPTN] is developing a more equitable system of allocating deceased donor organs. The new approach, continuous distribution, will provide organ offers by considering all factors that contribute toward a successful transplant, at once. We need your input on the next steps in developing this framework.”

At that point, I was three years and nine months into my journey with idiopathic pulmonary fibrosis and had been approved but deferred for a lung transplant due to COVID-19. My disease was progressing, and I knew my best option for living a longer life was a transplant.

I did participate in the exercise, and I can now see the results of my and others’ input in the OPTN’s new model for allocating donated lungs.

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The lung allocation score

Until recently, one hallmark of being listed for lung transplant was having your lung allocation score (LAS) calculated to help the United Network for Organ Sharing (UNOS) prioritize those on the waitlist. Scores ranged from 0 to 100, with a higher score indicating a higher priority for transplant. After I was listed, my LAS increased with each clinic visit until I received the call that lungs were available for me.

The LAS system considered four key attributes: medical urgency, distance from the donor hospital, candidate biology, and predicted one-year post-transplant survival. Potential transplant candidates would go through a sequential review, which meant that their priority could be determined by any one attribute.

If prioritization was based on distance, for example, a person with a low medical urgency who lived 230 nautical miles (nm) from the donor hospital might have been selected over someone with high medical urgency who lived 251 nm from the hospital.

A new day in organ allocation

Today, a new system is in place. Since March 9, the continuous distribution model considers multiple factors that contribute to a successful transplant at the same time, hopefully improving fairness and equity in the organ allocation process.

Under this framework, candidates will receive a composite allocation score (CAS). According to OPTN, the lung CAS considers five main goals that encompass nine candidate attributes. The score is calculated using a mathematical model, which weighs each attribute differently.

  1. Goal: Prioritize medically urgent candidates
    • Attribute: Expected one-year survival without transplant
  2. Goal: Improve post-transplant survival
    • Attribute: Expected five-year survival after transplant
  3. Goal: Increase transplant opportunities for patients who are medically harder to match
    • Attribute: Blood type
    • Attribute: Human leukocyte antigen (HLA) antibody sensitization
    • Attribute: Height
  4. Goal: Increase transplant opportunities for candidates who are younger than 18 or have previously donated an organ
    • Attribute: Pediatric age group
    • Attribute: Living donor
  5. Goal: Promote the efficient management of organ placement
    • Attribute: Travel efficiency
    • Attribute: Proximity

Is the new model an improvement?

I suppose this question is subjective. Because the organ allocation system is blinded to identities, I know nothing about my donor. It’s impossible for me to determine whether this new model would have affected the timing of my transplant.

In my view, the new continuous distribution framework is an improvement. Increasing the weight of medical urgency, with the goal of reducing waitlist deaths, is a positive thing. I especially want to celebrate two attributes that now factor into a candidate’s priority: being a pediatric patient or a prior living donor. I know several living donors, and the decision they made to improve and extend another person’s life was bound in love.

The lung-transplant community was the first to implement the CAS model, but it will roll out to other solid organs soon. My message to donor families is that OPTN is making a concerted effort to ensure that the organs you selflessly donated are put to the best use. Thank you for the love of your donation and for helping me make every breath count.

Note: Pulmonary Fibrosis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The opinions expressed in this column are not those of Pulmonary Fibrosis News or its parent company, BioNews, and are intended to spark discussion about issues pertaining to pulmonary fibrosis.


Adele B Friedman avatar

Adele B Friedman

Good explanation-thank you.

Samuel Kirton avatar

Samuel Kirton


Thanks for reading my column. I am glad you found the explanation helpful. Please return often.

Sam ...


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