Lung allocation score

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The lung allocation score or LAS is a numerical value used by the United Network for Organ Sharing (UNOS) to assign relative priority for distributing donated lungs for transplantation within the United States. The lung allocation score takes into account various measures of a patient's health in order to direct donated organs towards the patients who are in direst need of a lung transplant.

The LAS system replaces the older method within the United States of allocating donated lungs strictly on a first-come, first-serve basis, according to blood type compatibility and distance from the donor hospital. The older method is still used for patients under the age of 12.

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[edit] Lung allocation scoring method

The lung allocation score is calculated from an a series of formulas that take into account the statistical probability of a patient's survival in the next year without a transplant, how long that survival would be, the probability of survival following a transplant, and the projected length of survival post-transplant. A raw allocation score, summarizing all of the above values, is calculated, and finally this score is normalized to obtain the actual LAS, which has a range from 0 to 100.

[edit] Factors in calculating the LAS

There are many factors that are used to calculate the lung allocation score.

UNOS requires that the various medical results must be current, i.e. obtained within the last six months, or the relevant factor is assigned a zero value. Exceptions can be made if a patient is deemed unable to complete a test due to his or her current condition. In such a case, the physician must obtain permission from the UNOS Lung Review Board to submit a reasonable estimate of how the patient would perform.

In certain instances, a physician may petition the UNOS Lung Review Board to modify a patient's assigned LAS if it is felt that a patient's particular circumstances are not adequately represented by the regular LAS calculation system.

[edit] How the LAS score is used

The lung allocation score is an important part of the recipient selection process, but other factors are also considered. Patients who are under the age of 12 are still given priority based on how long they have been on the transplant waitlist. The length of time spent on the list is also the deciding factor when multiple patients have the same lung allocation score.

  • blood type compatibility - the blood type of the donor must match that of the recipient due to certain antigens that are present on donated lungs. A mismatch in blood type can lead to a strong response by the immune system and subsequent rejection of the transplanted organs. In an ideal case, as many of the human leukocyte antigens as possible would also match between the donor and the recipient, but the desire to find a highly compatible donor organ must be balanced against the patient's immediacy of need.
  • age of donor - The donated lung(s) must be large enough to adequately oxygenate the patient, but small enough to fit within the recipient's chest cavity. Therefore age is a consideration in the transplant process.


Donor age <12 Donor age 12-17 Donor age 18+
1st priority candidate Age <12 Age 12-17 Age 18+
2nd priority candidate Age 12-17 Age <12 Age <12
3rd priority candidate Age 18+ Age 18+


  • distance from the donor hospital - as donated lungs should be transplanted into the recipient within 4-6 hours of harvesting, ideally both donor and transplant hospitals should be relatively near each other.

[edit] An illustrative example

For example, a lung from a 16 year old donor would first be offered to the person in the age group 12-17 with the highest lung allocation score and matching blood type in the vicinity of the transplant center. If there no suitable recipient in that age group, it would next be offered to the highest LAS-scoring candidate who is under 12 years of age. Finally, it would be offered to the highest LAS-scoring person of age 18 or older. If there is no suitable candidate within the area, the lung may be offered to someone farther away, within certain time and distance constraints.

[edit] References

United Network for Organ Sharing

Transplantation edit
Types of Transplants: Allograft - Alloplant - Allotransplantation - Autotransplantation - Xenotransplantation

Tissue and Organs Transplanted: Organ transplant - Bone grafting - Bone marrow - Corneal - Face - Hand - Heart - Heart-Lung - Kidney - Liver - Lung - Pancreas - Penis - Skin grafting - Spleen

Related issues: Cellular memory - Biomedical tissue - Edmonton protocol - Eye bank - Graft-versus-host disease - Immunosuppressive drugs - Islet cell transplantation - Living donor liver transplantation - Lung allocation score - Machine perfusion - Medical grafting - Non-heart beating donation - Organ donation - Post-transplant lymphoproliferative disorder - Total body irradiation - Transplant rejection

Organizations related to Transplants: Human Tissue Authority - National Marrow Donor Program - United Network for Organ Sharing

People related to transplants: Isabelle Dinoire - Jean-Michel Dubernard - Gregory Scott Johnson - List of notable organ transplant donors and recipients