[citation needed] The LAS system replaces the older method within the United States of allocating donated lungs strictly on a first-come, first-served basis, according to blood type compatibility and distance from the donor hospital.
The final lung allocation score, which is meant to reflect the overall transplant benefit, incorporates this element as well.
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.
[citation needed] The lung allocation score is an important part of the recipient selection process, but other factors are also considered.
The length of time spent on the list is also the deciding factor when multiple patients have the same lung allocation score.