The U.S. Department of Health & Human Services Organ Procurement and Transplantation Network (OPTN) has released modified guidelines to their Lung Allocation Score (LAS) system, effective February 19, 2015.
Dr. Maryam Valapour, the Director of Lung Transplant Outcomes at the Cleveland Clinic in Cleveland, Ohio was instrumental in the analysis of the new LAS guidelines, and also has just coauthored the OPTN/SRTR 2013 Annual Data Report on the state of the lung transplant medicine.
The report, published in an American Journal of Transplantation Special Issue (Volume 15, Issue S2, pages 128, 2015 first published online: 27 January 2015 DOI: 10.1111/ajt.13200) is coauthored by Dr. Valapour of the Cleveland Clinic Department of Pulmonary Medicine Respiratory Institute at Cleveland, Ohio, along with other colleagues. The coauthors note that available lungs are allocated to adult and adolescent transplant candidates based on criteria of age, geography, blood type compatibility, and the lung allocation score (LAS), which reflects risk of wait-list mortality and probability of post-transplant survival.
They report that bilateral lung transplant remains the preferred procedure, representing approximately 70 percent of lung transplants in 2013, that both short-term and long-term survival have plateaued since the LAS’s original implementation of in 2005, and that as of June 30, 2013, nearly 11,000 recipients were living with a lung transplant in the US.
The coauthors also observe that lung transplant is increasingly used in treating patients who have end-stage lung diseases or are critically ill, and that lungs are allocated to US transplant candidates aged 12 years or older primarily on the basis of age, geography, blood type (ABO) compatibility, and the lung allocation score (LAS).
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Implemented in 2005, the LAS calculation reflects the risk of wait-list mortality while avoiding transplants in candidates whose likelihood of survival is poor, and applies to adolescent (aged 12-17 years) and adult (aged 18 years or older) candidates. They note that as of June 10, 2013, pediatric candidates (aged younger than 12 years) can ask for an exception from the national Lung Review Board and be assigned a LAS to give primary access to lung offers from adult and adolescent donors.
The biggest change under the revised guidelines is that people with pulmonary hypertension will be accorded higher priority. From her report, Dr. Valapour also explains that one of the biggest shifts seen in lung transplant medicine is that there are more older people on the list and much sicker people, so some changes in the system were needed in order to reflect that.
In an email interview, Dr. Valapour explained the reasoning behind the LAS changes in greater detail.
Lung Disease News: Is it any more difficult to match a patient with pulmonary hypertension with a donor than it is any other organ recipient?
Dr. Valapour: “Patients with pulmonary hypertension almost always require a bilateral lung transplant; therefore, donors who can donate only a single lung are not suitable for pulmonary hypertension patients. In that sense it is more challenging to find organs for patients with pulmonary hypertension than some others. However, the same can be said for patients with a number of other lung diseases such as Cystic fibrosis who also require bilateral transplants. “
Lung Disease News: What clinical/scientific aspect of pulmonary hypertension gives patients a higher LAS and thus higher priority for transplant?
Dr. Valapour: “The original Lung Allocation Score (LAS) system did not fully include all the parameters that capture the severity of illness and therefore risk of mortality of patients with pulmonary hypertension on the waiting list. Once that was recognized, a mechanism was developed by the OPTN/UNOS to give patients with pulmonary hypertension with a high risk of mortality a higher LAS score by the national Lung Review Board. The new Revised LAS which was implemented on February 19, 2015 includes measures of heart function and heart failure that will result in a more accurate predicted risk of wait-list mortality for this population. Patients with pulmonary hypertension are expected to have higher LAS under the revised LAS system.”
Lung Disease News: Are there many patients who were very close to being “the next in line” for a lung transplant who will now need to wait even longer due to a shift in priority?
Dr. Valapour: “The Scientific Registry for Transplant Recipients models changes in the US organ allocation system in order evaluate the possible impact of all changes before they go into effect. In simulations, the 30% of patients who were in front of the line for transplant were not impacted by the change in the LAS. Of course it is inevitable that some patients will have to wait longer for a transplant but they will likely not be the sickest among the waiting list patients. However, it is important to remember that these are simulations and that real-time impact of the Revised LAS will be closely monitored.”
Lung Disease News: How is the rate of pulmonary hypertension diagnosis compared to the diagnosis rates of ‘competing’ diseases for lung transplants?
Dr. Valapour: “At the end of 2013, patients with pulmonary hypertension (group B in the figure below-right) represented 6.2% of patients awaiting a lung transplant in the US. Citation is below the table – this is the annual report from the Scientific Registry of Transplant Recipients (SRTR) describing the trends in US lung transplant.”
In summary, the LAS revisions mainly incorporate policy changes that have been developed based on numerous proposals advanced over several years, including modifications to variables used in the LAS calculation and to the relative weight of the variables used to predict risk of death in the next year without transplant and in the first year after transplant. The revised LAS will further improve the survival prediction for all diagnostic groups, with these effects likely have the most impact on candidates in diagnosis group B.
New Data Variables
The new LAS revision is largely based on variables in transplant programs already reporting to the OPTN for lung transplant candidates. Provision is already in place for transplant programs to report cardiac index (CI) and central venous pressure (CVP) their lung candidates in WaitlistSM to the OPTN. As of February 19, these variables are now being factored into the LAS calculation, and in addition, the system now allows for CVP data obtained through means other than a heart catheterization to be entered.
Total bilirubin is the only new variable added to the calculation that was not previously being collected in the system. Bilirubin is collected and stored serially, like PCO2, and attending clinicians can now add the candidate’s current bilirubin value, as well as historical values. Serum creatinine is also collected and stored serially, and as with bilirubin and PCO2, transplant programs can report current and historical serum creatinine values. While entry of historic values for the serial data (PCO2, bilirubin, and serum creatinine) is optional, these values may impact a candidate’s Lung Allocation Score.
Missing, Expired, or Below Threshold Data
Previously, if data were missing or expired for either the candidate’s functional status or assisted ventilation fields, the candidate’s LAS was set to zero. Under the updated system, policy default values for these variables are used in the calculation when the data are missing or expired.
Lung Diagnoses
In the LAS system, lung diagnoses are divided into four diagnosis categories: A) obstructive lung disease; B) pulmonary vascular disease; C) cystic fibrosis; and D) restrictive lung diseases. The list of lung diseases and their diagnosis groupings are largely the same as the previous LAS system, but more diagnoses have been added.
Added to Group B
– Pulmonary capillary hemangiomatosis
Added to Group D
ABCA3 transporter mutation
– Idiopathic interstitial pneumonia (IIP), with at least one or more of the following disease entities:
– Acute interstitial pneumonia
– Desquamative interstitial pneumonia
– Nonspecific interstitial pneumonia
– Respiratory bronchiolitis-associated interstitial lung disease
– Pulmonary lymphangiectasia (PL)
– Secondary pulmonary fibrosis (specify cause)
– Surfactant protein C mutation
The OPTN/SRTR 2013 Annual Data Report can be downloaded here (PDF format):
http://onlinelibrary.wiley.com/doi/10.1111/ajt.13200/full
For more information, on the LAS guidelines revision see:
http://optn.transplant.hrsa.gov/news/preparing-your-patients-for-changes-to-the-lung-allocation-system/
About Dr. Valapour
Dr. Valapour, named a Fellow of the American College of Chest Physicians in 2010, is a physician-scientist with expertise in transplant medicine. Her clinical work is focused on caring for lung transplant candidates and recipients, with a research focus on the ethics and policies of organ transplantation – her work in these areas funded by the NIH and Department of Health and Human Services. Dr. Valapour serves as Senior Investigator for Lung Transplant for the Scientific Registry of Transplant Recipient (SRTR), in which capacity she works to evaluate the influence of policy on the practice of lung transplant and performs research to inform revision and refinement of US thoracic transplant allocation policy. She also serves on a number of national organ transplant committees.