The match run

The match run is the computer-generated, organ-specific, rank-ordered list of transplant candidates that the Organ Procurement and Transplantation Network (OPTN) computer system produces for each individual deceased-donor organ.[1][2] When an organ procurement organization (OPO) enters a donor's clinical, laboratory, and anatomical data into the national system, the system applies the relevant OPTN allocation policy and returns an ordered list of candidates to whom that specific organ will be offered, beginning with the highest-ranked candidate.[1][2] As UNOS describes it, "this match is unique to each donor and each organ," because the ranking factors and the donor's characteristics differ for every organ from every donor.[1]

The match run is the operational expression of allocation policy: the order in which candidates appear is dictated entirely by OPTN policy, and that policy, under the federal OPTN Final Rule (42 CFR §121.8), permits only medical and logistical ranking factors, not a candidate's place of residence or listing except where geography is medically necessary.[3][1] This article describes what the match run is, the factors it uses, and how an organ is offered down the list; the policy framework behind it is described in OPTN allocation policy.

What the match run is

A match run is not a single standing waiting list that is worked from top to bottom for every donor.[1][4] Instead, the national waiting list is a pool of candidates, and a fresh, donor-specific ranked list is generated each time an organ becomes available.[1][4] The same candidate may appear near the top of one donor's match run and far down another's, because ranking depends on how that candidate's characteristics (blood type, body size, urgency, sensitization, distance from the donor) interact with that particular donor's characteristics.[1][4]

The list is produced by the OPTN's secure information system (historically operated by UNOS and known as UNet, with the donor- and offer-facing component called DonorNet).[2][4] An OPO recovering a deceased donor enters the donor's data and requests a match run; the system confirms that the required donor parameters are present and then runs the organ-specific allocation algorithm to produce the ranked candidate list.[2][4]

Factors used to rank candidates

The match run ranks candidates using medical and logistical factors that vary by organ; UNOS summarizes the principal factors as follows.[1]

Factors considered for every organ include:[1]

• Blood type (ABO) compatibility between donor and candidate;
• Body size (matching donor organ size to candidate);
• Medical urgency (how sick the candidate is, expressed through an organ-specific measure);
• Distance between the donor hospital and the candidate's transplant hospital; and
• Pediatric status (priority for child candidates for certain organs).

Additional organ-specific factors include:[1]

• Kidney: waiting time, immune sensitization measured by calculated panel-reactive antibody (cPRA), prior living-donor priority, and survival benefit (longevity matching);
• Lung: medical urgency, expected post-transplant survival, cPRA, and height/size match, combined since 2023 into a single Composite Allocation Score;
• Liver and heart: medical urgency (the MELD/MELD 3.0 score for liver; the six-status system for heart), distance from the donor hospital, and pediatric status.

Because these factors are organ-specific, the match run is generated by a different algorithm for each organ, even from the same donor.[1][2] All of the factors are medical or logistical; consistent with 42 CFR §121.8, allocation "shall not be based on the candidate's place of residence or place of listing" except to the extent geography is required by sound medical judgment and best use of organs.[3]

How an organ is offered down the list

Once the ranked list is produced, the OPO offers the organ to transplant programs in match-run order, starting with the first candidate.[4] The mechanics, per UNOS, are:[4]

• Donation professionals at the OPO use DonorNet to send an electronic organ offer to the transplant team caring for the first candidate on the list.
• The transplant team reviews the donor record to evaluate the organ's suitability for that candidate and chooses to accept or decline the offer.
• By OPTN policy, the transplant team has a limited time (UNOS describes a one-hour window) to respond before the organ is offered to the next candidate.
• If the organ is declined, the OPO continues offering it to candidates in the order they appear on the match run until it is accepted.[4]

An organ may be declined for many reasons, including the candidate's condition at the time of the offer, the organ's quality, or logistical constraints; declines are common and expected, and the sequential offer process is designed to find a suitable, willing recipient quickly while the organ remains viable.[1][4] The time pressure is real because organ viability is limited by cold-ischemia time, which is one of the medical reasons geography (distance from the donor hospital) appears as a ranking and weighting factor in allocation policy.[1][3]

Relationship to allocation policy and continuous distribution

Because the match run mechanically applies policy, changes in OPTN allocation policy change the order candidates appear in.[1][3] Under the historical system, candidates were grouped into discrete tiers and then ordered within each tier, with hard geographic boundaries (the donation service area and OPTN region) determining who was considered "local."[5] Under continuous distribution, adopted first for lung in 2023, the discrete tiers and hard boundaries are replaced by a single weighted composite score, so the match run is ordered by a continuous numeric ranking rather than by a sequence of categorical brackets.[5][6] The match run remains the same fundamental object, a donor- and organ-specific ranked list, but the way candidates are ordered within it reflects whichever allocation framework is in force for that organ.[5][6]

See also

• OPTN allocation policy
• Continuous distribution and the Composite Allocation Score
• MELD / MELD-Na / MELD 3.0 (and PELD)
• Heart allocation status system
• Geographic distribution and acuity circles
• Human leukocyte antigen (HLA) and tissue typing
• The donation pathway

References

• UNOS. How we match organs. https://unos.org/transplant/how-we-match-organs/
• HRSA / OPTN. Donor matching system. https://www.hrsa.gov/optn/patients/organ-donation/donor-matching-system
• 42 CFR §121.8, Allocation of organs (OPTN Final Rule). Legal Information Institute, Cornell Law School. https://www.law.cornell.edu/cfr/text/42/121.8
• UNOS. Is it really a list? What determines how organs are allocated, and the role UNOS technology plays in it. https://unos.org/news/is-it-really-a-list-what-determines-how-organs-are-allocated-and-the-role-unos-technology-plays-in-it/
• HRSA / OPTN. Continuous Distribution. https://www.hrsa.gov/optn/policies-bylaws/policy-issues/continuous-distribution
• UNOS / OPTN. New lung allocation policy in effect. https://unos.org/news/new-lung-allocation-policy-in-effect/