Why Can a MELD Exception Score Change With the Donor? Understanding MMaT in Liver Allocation

By Brooke Wallace, BSN, RN, CCRN — founder of CPTCexam.com. ICU RN; previously worked as an Organ Procurement Coordinator and authored CPTC handbooks. CPTCexam.com is independent exam-prep and is not affiliated with or endorsed by ABTC.

A Liver Allocation Detail That Surprises New OPCs

Here is a counterintuitive point many new organ procurement coordinators learn the hard way:

A liver candidate’s MELD exception score may not be a single fixed number.

For many candidates with approved MELD exceptions, the score used on a match run is tied to the Median MELD at Transplant (MMaT) associated with the donor hospital where the liver is recovered—not to one permanent number that follows the candidate everywhere.

On September 23, 2026, HRSA/OPTN updated those MMaT values for donor hospitals nationwide. That update is a good reason to revisit the bigger teaching question:

Why should the location of the donor hospital affect a recipient’s exception score?

First: What Is MELD?

MELD stands for Model for End-Stage Liver Disease. It is the score used to prioritize most liver transplant candidates age 12 and older. Higher scores generally mean greater medical urgency—greater risk of death without transplant.

The current adult calculation (often called MELD 3.0) uses laboratory values including bilirubin, creatinine, INR, sodium, and albumin, plus a sex adjustment for adult candidates. Age matters mainly for which scoring pathway applies (MELD for candidates 12 and older; PELD for younger pediatric candidates)—not as a continuous “age points” term you plug into the adult formula.

Keep this section short on purpose. The real subject of this article is exception scoring and MMaT, not memorizing the MELD equation.

What Is a MELD Exception?

Some liver diseases create substantial transplant urgency that laboratory MELD alone does not fully capture. Certain candidates with hepatocellular carcinoma (HCC) and other OPTN-defined exception diagnoses are examples of situations where policy allows an exception pathway.

Core concept:

An exception score is meant to let allocation priority better reflect the candidate’s transplant need when the calculated (lab) MELD is not enough.

Then comes the twist that trips up new OPCs:

Many exception scores are linked to MMaT rather than permanently assigned as one fixed whole number.

What Does MMaT Mean?

Median MELD at Transplant (MMaT) is the median MELD score at which liver transplantation has recently occurred in the transplant environment around a particular donor hospital.

MMaT acts as a reference point for many exception candidates. A common policy pattern awards something like MMaT − 3.

Simple teaching example (illustrative numbers, not a real hospital lookup):

  • Exception policy awards MMaT − 3
  • Relevant donor hospital MMaT = 30
  • Candidate’s exception score on that match run = 27

Another donor hospital can have a different MMaT—so the same approved exception can produce a different numerical score on a different offer.

Why Is MMaT Based on the Donor Hospital?

This is the key teaching section.

Historically, transplant access—and the MELD level at which candidates actually receive transplants—has varied geographically. MMaT was developed so many exception scores track the transplant environment surrounding the donor hospital, rather than giving every exception candidate the same numerical priority nationwide.

In other words, the system tries to use a locally relevant benchmark for transplant access when it builds certain exception scores.

OPTN has calculated MMaT using recent liver-transplant activity within a geographic radius around each donor hospital (commonly described as about 150 nautical miles in OPTN/UNOS education materials), and those values are revised periodically as transplant patterns change. Since mid-2022, that reference has been anchored to the donor hospital generating the match—not the transplant hospital where the candidate is listed.

Why the Candidate’s Score Can Change From One Offer to Another

This is the section that should stick.

Donor Hospital A

  • MMaT = 29
  • Candidate exception = MMaT − 3
  • Match-run score = 26

Donor Hospital B

  • MMaT = 32
  • Same candidate
  • Same approved exception
  • Match-run score = 29

The candidate has not become sicker overnight. The diagnosis did not change. The exception approval did not vanish. The reference value changed because the donor hospital changed.

HRSA specifically notes that for these candidates, the exact exception score may not be known until the match is run for an individual donor.

That sentence alone is worth more than memorizing the acronym.

Why This Matters to Organ Procurement Coordinators

An OPC looking at a liver match run may wonder:

  • Why did this candidate suddenly appear with a different MELD?
  • Why isn’t the exception score the same as it was on another donor?
  • Why does the match sequence look different for this liver?

The answer may be MMaT.

Key teaching point:

Match runs aren’t simply a static ranking of recipients. Certain allocation variables depend on characteristics or location associated with the individual donor.

That is a more useful lesson for a newer coordinator than simply memorizing what MMaT stands for.

What Changed on September 23, 2026?

Here is the news hook, kept in its proper place.

HRSA/OPTN updated the MMaT values for every donor hospital nationwide, effective September 23, 2026. Those values are updated periodically as transplant patterns change. An updated data table is available on the Liver and Intestine resource page of the OPTN website.

Therefore, some candidates whose exception scores are based on MMaT may now receive a different numerical score on current match runs than they would have under the previous MMaT table.

Important distinction:

The underlying exception policy did not necessarily rewrite itself overnight—the reference values did.

Primary notice: HRSA/OPTN — Updated Median MELD at Transplant Scores Effective Sept. 23, 2026.

What About Pediatric Candidates?

Median PELD at Transplant (MPaT) works differently.

For the September 23, 2026 update:

  • National MPaT remains 31
  • It is calculated nationwide
  • It is not dependent on donor-hospital location

Useful comparison:

  • MMaT = donor-hospital–specific
  • MPaT = national

Why This Matters Beyond Memorizing Allocation Rules

Zoom out.

Liver allocation is trying to balance several competing goals at once:

  • Medical urgency
  • Fair access
  • Geographic variation in transplant practice
  • Appropriate recognition of exception diagnoses
  • Efficient organ placement

MMaT is one concrete example of how allocation policy turns those principles into an actual match sequence. It is also why transplant allocation can feel much more complicated in practice than it appears in a classroom or textbook chapter.

What OPCs Should Remember

For the OPC:

  • MELD and MELD exception scores are not the same thing.
  • Many exception scores are based on MMaT.
  • MMaT varies by donor hospital.
  • Therefore, an exception candidate’s score can change between donor match runs.
  • You may not know the candidate’s actual exception score until the donor-specific match is generated.
  • MMaT values were updated nationwide September 23, 2026.

Conclusion

One of the biggest shifts from learning allocation in a classroom to working actual donor cases is realizing how dynamic the match process can be.

A candidate can have the same diagnosis, the same exception approval, and the same clinical condition—yet appear with a different allocation score depending on the donor involved.

Understanding why that happens is far more useful than simply memorizing what MMaT stands for.

If you are a new OPC building confidence in liver allocation—or studying for the CPTC exam—CPTCexam.com has free and structured prep materials, including CPTC exam study resources and the OPO New Coordinator to CPTC-Ready Curriculum ($200). Use what helps you read the next match run with clearer eyes.

Field-honest allocation education from someone who has done the work—CPTCexam.com.

Sources

  1. HRSA / OPTN. Updated Median MELD at Transplant Scores in Effect Sept. 23; Median PELD at Transplant Score Unchanged. Sept. 23, 2026. https://www.hrsa.gov/optn/news-events/news/updated-median-meld
  2. OPTN / UNOS. Median MELD at transplant now based around donor hospital (June 28, 2022 policy context). https://unos.org/news/median-meld-at-transplant-based-donor-hospital-june-28/
  3. OPTN. Report lists median MELD at transplant score for each donor hospital (150 NM / periodic update context). https://optn.transplant.hrsa.gov/news/report-lists-median-meld-at-transplant-score-for-each-donor-hospital
  4. HRSA / OPTN. Questions and Answers About Liver Allocation (patient-facing MMaT−3 explanation). https://www.hrsa.gov/optn/patients/resources/liver/liver-allocation-faqs
  5. OPTN. MELD Calculator. https://optn.transplant.hrsa.gov/data/allocation-calculators/meld-calculator
Back to blog