Researchers reported that patients with pulmonary arterial hypertension (PAH) remain least likely to receive a lung transplant and hence most likely to die while on the waiting list, despite recommendations made in 2015. The findings were published in the American Journal of Respiratory and Critical Care Medicine.

PAH, characterized by elevated pulmonary vascular resistance, is potentially fatal. Despite advancements in the therapeutic landscape, lung transplantation remains an important option for patients with severe disease. 

To make lung transplantation more equitable, the Lung Allocation Score (LAS) was introduced by the United Network for Organ Sharing (UNOS). This score was intended to help physicians make the decision on which cases to prioritize in the allocation of lung transplants. In 2015, this score was revised again to better reflect the severity of PAH and to increase waitlist survival. 

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“Despite these efforts, recent studies demonstrate that patients with PAH continue to comprise the majority of exception requests, and survival is worse in patients with PAH when exceptions are not approved, a discrepancy not found in other diagnostic groups,” the authors of the study wrote. 

Read more about PAH epidemiology 

They hence conducted a study to determine if the LAS made a significant difference in how lung transplants were allocated among patients with PAH. They obtained data from the Organ Procurement and Transplantation Network. They divided the study population into patients who were listed prior to the 2015 LAS revision and those who were listed after. The research team assessed if LAS was a credible scoring model to assess the needs of patients with PAH who were on the lung transplantation waiting list. 

The results of the study revealed that LAS was a modest success in that it improved waitlist mortality across different diagnostic categories. The 2015 revision benefited patients with PAH by highlighting specific parameters of disease progression in PAH. 

“However, the 2015 LAS Revision did not fully achieve equitable access to transplant for patients with PAH,” the researchers wrote. “Participants with PAH still had the highest waiting list mortality and lowest likelihood of transplant in all three of our sensitivity analyses.”

This study highlights the need for future LAS revisions to go even further in providing equitable care for patients with PAH. 


Kolaitis NA, Chen H, Calabrese DR, et al. The Lung Allocation Score remains inequitable for patients with PAH, even after the 2015 revisionAm J Respir Crit Care Med. Published online September 12, 2022. doi:10.1164/rccm.202201-0217OC