A lung disease patient’s priority on the national organ transplant waiting list is based on a weighted score calculated using multiple factors, with the biggest drivers being medical urgency and the likelihood of survival past five years if they are transplanted. But when patients with secondary pulmonary hypertension (SPH) are recognized in the system with that diagnosis rather than their primary lung disease, it could hurt their chances of receiving a lung transplant, according to new research by Luke Benvenuto, MD, a transplant pulmonologist at NewYork-Presbyterian and Columbia.
Dr. Benvenuto and his colleagues analyzed data from 2005 to 2021 from the United Network for Organ Sharing (UNOS), the organization that manages the nation’s transplantation network, and found that patients receive transplants at a lower rate when their diagnosis is listed as SPH instead of a primary diagnosis like interstitial lung disease (ILD), which can cause SPH. Below, Dr. Benvenuto shares why he believes retiring SPH from the lung allocation criteria could help save more patients with advanced lung disease.
Why Using an SPH Diagnosis Is Counterproductive
When doctors list a patient for a lung transplant, we are trying to advocate for our patients as much as we can within the system set in place for the national transplantation network. This means we have to capture the complete nature of the patient’s disease so they can receive a score that accurately represents their level of sickness. Waitlist urgency and post-transplant survival can vary significantly based on the provided diagnosis.
By nature, secondary pulmonary hypertension is always going to be accompanied by another disease. However, under the Lung Allocation Score (LAS) that was in place when this data was recorded, an SPH diagnosis sometimes gave patients a slightly higher starting score than the primary lung disease that led to their SPH. In 2023, the scoring system was changed to the lung Composite Allocation Score (CAS) and took additional factors into account, but even with these changes, some patients would still start with a higher score when listed with SPH. As a result, many physicians continue to list SPH as a patient’s diagnosis instead of a primary diagnosis like ILD or chronic obstructive pulmonary disease (COPD).
Until now, we did not have data to back up whether this practice was successful, but as a result of this analysis, we now know that SPH does not help position our patients higher; rather, it creates ambiguity for clinicians and researchers and can actually hurt patients by potentially lowering their score, thereby decreasing their chances of receiving a transplant.
We came to these conclusions by comparing outcomes for patients listed in UNOS under SPH with the outcomes of patients who were listed under primary pulmonary hypertension, and with patients whose diagnosis was listed as having ILD or COPD but who also met the criteria for SPH.
We found that patients with both ILD and SPH were more likely to receive a transplant when their diagnosis was listed as ILD rather than SPH. We also noticed that when providers listed a patient’s diagnosis as SPH, their score may start higher when they are first listed, but as the patient becomes sicker while they wait to receive a new organ, it actually drops.
That’s because patients with ILD have relatively short pretransplant survival times compared to patients with other lung diseases and their oxygen requirement rises quickly, which increases the medical urgency portion of their score. However, patients listed with an SPH diagnosis are treated as pulmonary hypertension (PH) patients rather than ILD patients, and a rising oxygen requirement does not increase their score as dramatically. Therefore, patients with ILD who are listed under the SPH diagnosis have lower waitlist urgency scores and, consequently, lower transplant rates, causing them to spend more time deteriorating on the waitlist.
How Removing SPH from Lung Allocation Criteria Can Improve Clarity and Accuracy
In principle, the predictive algorithms used to prioritize lung transplant patients should function so that the sicker a patient is, the higher they are placed on the list. But SPH can have many root causes, and by not pinpointing what they are, we are reducing clarity in the lung allocation system. SPH alone is too heterogeneous of a diagnosis to help predictive models do their jobs in a way that prioritizes the patients in most dire need.
If we remove SPH from the list of diseases in the system, doctors will be unable to choose it accidentally or incorrectly as a diagnosis, thus preventing them from inadvertently creating a disadvantage for their patients. Removing SPH also comes with benefits for future research: Without the SPH label creating ambiguity, it will be easier to accurately categorize data for patients with COPD and ILD.
But until everyone who cares for patients on the lung transplant list agrees that SPH should be removed, we will continue to experience issues with delayed transplantations and ambiguous data for research purposes. So, for as long as SPH remains a diagnostic option, I urge physicians to consider listing their patients under their primary diagnosis — whether it is ILD, COPD, or another lung disease — to both better serve the patient and advance pulmonology research.
