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Updated Cohort for Calculation of the Lung Allocation Score (LAS)

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What is current policy and why change it?

OPTN lung allocation policy for candidates 12 years and older uses the Lung Allocation Score (LAS) as a factor that impacts priority in organ offers. The data used for the score has not been updated in over 10 years. Additionally, some factors used to calculate LAS do not help predict waitlist or post-transplant survival and should be removed from the calculation.

Updated Cohort for Calculation of the Lung Allocation Score

Dr. Erika Lease, Chair of the OPTN Lung Transplantation Committee, reviews the Updated Cohort for Calculation of the Lung Allocation Score policy proposal.

Terms you need to know

  • Lung Allocation Score (LAS): In the OPTN lung allocation system, every lung transplant candidate age 12 and older receives a lung allocation score. The LAS is used with blood type and the distance between the candidate and the donor hospital to determine priority for receiving a lung transplant. The score is made up of factors that help determine a candidate’s waitlist urgency and post-transplant survival.
  • Waitlist Urgency:A candidate’s risk of death if they do not receive a transplant.
  • Post-Transplant Survival: Likelihood of recipient to survive for one year after receiving their organ.

Click here to search the OPTN glossary

What’s the proposal?

  • Update the patient population data used to determine the LAS to include candidates and recipients from March 1, 2015 to March 31, 2018
  • Remove factors that no longer help predict waitlist or post-transplant survival

What’s the anticipated impact of this change?

  • What it’s expected to do
    • Update the data to reflect more recent patient populations
    • Provide up-to-date LAS data to inform the Lung Transplantation Committee’s project to develop a new allocation system for lungs
    • Change some candidates’ LAS to better reflect their need for transplant
  • What it won’t do
    • Will not change data collection elements

Themes to consider

  • Potential for factors used in calculating LAS to become more or less important
  • How often patient population data should be updated

Provide feedback

Overview

Status: Public Comment

Sponsoring Committee: Lung Transplantation Committee

Strategic Goal: Improve waitlisted patient, living donor, and transplant recipient outcomes

Contact:

Sara Rose Wells

Comments

Andrew Rivard | 08/24/2020

The outcome of the Lung Allocation Score is a composite number of acuity factors leading to a ranking of recipients. The score result should ideally tie to something that is testable as a hypothesis and comparable to prior publications, for example, 1 yr and 5 yr post transplant survival. The outcome of the composite number thus should ideally be able to produce an estimated 1yr and 5 yr survival rate (+/- SD). Therefore the patient with the highest composite score can be compared not only on their estimated survival; but their actual survival following transplantation. Thus the new cohort of transplant patients using the continuous distribution model can assist revision of the new scoring model by comparing estimated to actual survival. Furthermore, the new paradigm can be quickly compared with the prior transplant patient survival using the DSA model without having to wait a year.

Region 4 | 08/26/2020

Region 4 vote: 4 Strongly Support, 10 Support, 9 Neutral/Abstain, 0 Oppose, 0 Strongly Oppose This proposal was on the non-discussion agenda for the regional meeting.

Region 5 | 08/28/2020

Region 5 vote: 4 Strongly Support; 19 Support; 8 Neutral/Abstain; 0 Oppose; 0 Strongly Oppose. No comments

Anonymous | 09/01/2020

Being a candidate for a lung transplant I agree that allocation scores should be revised That however is not the only issue. People that have great insurance have an edge by being double listed. In todays society we have the ability to transfer donors lungs anywhere in the United states yet we have regions which are unfairly limited. Many candidates in region 5 have short wait times and have lower LAS allocation scores yet they are given lungs ahead of those that are in grater need. I myself have waited almost 4 years. Those who get on the list in region 6 go to region 5 and wait on occasion less than 30 days and these are candidates that have the same diagnosis and lowers LAS acores. That is what should be addressed.

Region 7 | 09/10/2020

Region 7 vote: 7 Strongly Support, 4 Support, 3 Neutral/Abstain, 0 Oppose, 0 Strongly Oppose No Comments

Region 3 | 09/15/2020

Region 3 vote: 0 Strongly Support, 15 Support, 10 Neutral/Abstain, 0 Oppose, 0 Strongly Oppose This proposal was on the non-discussion agenda for the regional meeting.

Region 8 | 09/22/2020

Region 8 vote: 4 strongly support, 9 support, 6 neutral/abstain, 0 oppose, 0 strongly oppose

American Society of Transplantation | 09/24/2020

The American Society of Transplantation supports this proposal, but offers the following comments and recommendations for consideration: This intent of this proposal is to update the variables, coefficients, and probabilities used in calculating the lung allocation score (LAS). An additional goal is the refinement of variables to those that are predictive within the waitlist mortality and post-transplant mortality models. The current iteration of the LAS is based up on a patient cohort that is now nearly 12 years old. The updated cohort for LAS calculation includes candidates and recipients from March 1, 2015 through March 30, 2018. Given that there were substantial changes made in 2008 it might have been instructive to include in the current proposal more information about the effects of those changes? We should have more than ten years of data to consider. For example, in what ways did removal of the FVC, or the addition of cardiac index, affect candidate selection in subsequent years? Several variables were identified as non-predictive due to small numbers of candidates or recipients. Waitlist variables proposed for removal include: obliterative bronchiolitis; lymphangioleiomyomatosis; Eisenmenger’s syndrome; and Bilirubin increase > 50%. Post-transplant variables proposed for removal include: lymphangioleiomyomatosis; creatinine increase > 150%; and Eisenmenger’s syndrome. - Our adult pulmonology representatives noted that the removal of variables due to small numbers of candidates or recipients is reasonable and appropriate. We agree with this change as well as continued collection of data with reference to these variables for future assessment. - Our pediatric pulmonology representatives noted that the removal of certain waitlist variables due to “small numbers” is a statistical practice that is different than the removal of variables because they have been proven to be accounted for by other variables. For example, they are not arguing, that Eisenmenger’s physiology is irrelevant; rather, simply, that they cannot prove whether it is relevant. Given that there might be a delay of ten years or more until there is further significant revision of the LAS, they suggest that we should be open to the possibility that further research will prove the relevance of some of these “orphan variables.” They would expect that allocation could be adapted accordingly to such a contingency (including, for example, another LAS revision, or the accommodation of exception requests based on these understudied variables). Several variables identified in the previous cohort were noted to have reversed sign (changed from positive to negative or negative to positive prediction of mortality) in the updated cohort. Waitlist survival variables in this category include: pulmonary fibrosis, other; diabetes; FVC <80% spline, group D; cardiac index < 2 L/min/m2; and CVP > 7, spline group B. The Committee proposes to remove 4/5 of these variables with the exception of pulmonary fibrosis, other. This hazard ratio for waitlist mortality for pulmonary fibrosis, other changed from -0.21 (p= 0.6297) to 0.21 (p=0.2093). This variable was retained in the model as the committee felt that the change in hazard ration could be consistence with their medical experience. - The removal of cardiac index <2 L/min/m2 may have adverse effects on patients in group B. In other models this parameter has been shown to correlate positively with mortality in pulmonary hypertension (particularly group 1 PAH). Was this variable analyzed separately for group B patients alone and was consideration given to retaining this variable for group B patients only. - Retention of pulmonary fibrosis other. Group D includes many different diagnosis codes and the category of pulmonary fibrosis, other is the most vague and therefore may be quite heterogeneous in composition. It is unclear how this diagnosis category is utilized by centers and effort to use more specific coding should be encouraged. The hazard ratio for this variable for mortality switched from positive to negative but without significant p-values. As there is no statistical correlation with mortality in the model, and this category is not very clearly defined we question the decision to retain it in the model. Post-transplant survival variables in this category include: pulmonary fibrosis, other; sarcoidosis, PA>30; sarcoidosis, PA <=30; and functional status, no assistance. The Committee proposes removal of pulmonary fibrosis, other; and functional status, no assistance. These variables were noted to no longer be predictive based upon high p-values. The sarcoidosis variables changed from negative to positive hazard ratios for post-transplant 1-year mortality. The sarcoidosis variables were retained as they were noted to be still predictive (p<0.0001 for sarcoidosis, PA > 30) or possibly predictive (p = 0.0736 for sarcoidosis PA <= 30) based upon low p-values and the Committee felt that the findings of the model were consistent with medical expertise. Implementation Considerations - Requested feedback: The Committee would like feedback regarding whether there is a benefit to waiting to implement changes concurrently with continuous distribution. - There does not appear to be a clinical justification for delay in implementation of changes to the model. Therefore, the decision of whether to implement changes now or concurrently with continuous distribution may largely be based upon the ability to analyze the impact of these changes in the future. Potential impact on select patient populations: - As noted above, the removal of cardiac index <2 could adversely affect group B candidates. However, this does not appear to be apparent in figure 2. - While the LAS model appears to identify and prioritize the highest risk patients it is less sensitive in its ability to stratify and identify risk amongst certain groups of patients, particularly those with COPD and cystic fibrosis resulting in large cohorts of patients with minimal difference in LAS values. Future incorporation of other disease specific variables into the model could help to more accurately reflect prognosis for such patient groups. Additional feedback requested: Are the appropriate variables being removed from the calculation? - See comments above re.: cardiac index < 2 and pulmonary fibrosis, other. Should the committee add any transition procedures to protect any specific population - No recommendations re. transition procedures. The Committee may wish to remind transplant centers of the potential to request a LAS adjustment when they are concerned that the patient’s transplant urgency is not reflected in their LAS>. - The pediatric practitioners did not feel that there was a need for transition procedures to protect our populations. We would expect, however, given the drop in LAS rank for diagnosis group A candidates, that there will be ongoing analysis to ensure that there is not a significant increase in waitlist mortality following implementation of the current proposal.

Region 1 | 09/24/2020

Region 1 vote: 4 Strongly Support, 3 Support, 5 Neutral/Abstain, 0 Oppose, 0 Strongly Oppose Comments: No Comments

Region 2 | 09/25/2020

Region 2 vote: 7 Strongly Support, 14 Support, 9 Neutral/Abstain, 0 Oppose, 0 Strongly Oppose Comments: No comments