The Secondary Pulmonary Hypertension Diagnosis is Not Useful in Lung Allocation

In lung transplant, the United Network for Organ Sharing (UNOS) contains a diagnosis of secondary pulmonary hypertension (SPH). SPH and pulmonary arterial hypertension are treated the same in the allocation scoring system. It is not clear whether utilizing the SPH diagnosis instead of the primary diagnosis is helpful to patients or providers.

Analysis of UNOS data from May 2005 through July 2021, comparing patients listed under the SPH diagnosis with patients listed under COPD and interstitial lung disease (ILD) who met criteria for PH (COPD-PH and ILD-PH, respectively), as well as patients listed under pulmonary arterial hypertension (primary pulmonary hypertension, PPH). Competing-risk analysis examined waitlist and post-transplant outcomes. An exploratory analysis of UNOS spirometry data was performed.

Compared to patients listed under the SPH diagnosis, patients with ILD-PH were more likely to undergo transplantation (adjusted HR: 1.34, 95% confidence interval: 1.16-1.54, P < .001), with no significant difference comparing the SPH diagnosis to PPH or to COPD-PH. Waitlist mortality did not vary between groups. Post-transplant survival was lower in patients with PPH (adjusted HR: 1.35, 95% confidence interval: 1.04-1.75, P = .025), with no significant difference comparing the SPH diagnosis to COPD-PH or ILD-PH. Spirometry failed to demonstrate a clear phenotype within the SPH diagnosis.

In an adjusted analysis, patients with advanced lung disease and secondary PH were more likely to undergo transplantation when listed for ILD than when listed under the SPH diagnosis. The SPH diagnosis is too clinically heterogeneous to be useful in predictive models and should be considered for removal from UNOS.