Disparities in Lung Transplant among Patients with Idiopathic Pulmonary Fibrosis: An Analysis of the IPF-PRO Registry

Rationale: Lung transplant offers the potential to extend life for patients with idiopathic pulmonary fibrosis (IPF); yet, this therapeutic modality is only available to a small proportion of patients. Objectives: To identify clinical characteristics and social determinants of health that differentially associate with lung transplant compared with death in patients with IPF. Methods: We evaluated data from the Idiopathic Pulmonary Fibrosis Prospective Outcomes (IPF-PRO) Registry, a multicenter U.S. registry of patients with IPF that was diagnosed or confirmed at the enrolling center in the previous 6 months. Patients were enrolled between June 2014 and October 2018. Patients who were listed for lung transplant were not eligible to enroll in the registry, but patients could be listed for transplant after enrollment. We performed a multivariable time-to-event analysis incorporating competing risks methodology to examine differential associations between prespecified covariates and the risk of lung transplant versus death. Covariates included factors related to lung transplant eligibility, clinical characteristics of IPF, and social determinants of health. Covariates were modeled as time independent or time dependent as appropriate. Results: Among 955 patients with IPF, event rates of lung transplant and death were 7.4% and 16.3%, respectively, at 2 years. Covariates with the strongest differential association were age, median zip code income, and enrollment at a center with a lung transplant program. Lung transplant was less likely (hazard ratio [HR], 0.13 [95% confidence interval (CI), 0.06-0.28] per 5-yr increase) and death more likely (HR, 1.41 [95% CI, 1.22-1.64] per 5-yr increase) among those older than 70 years of age. Higher median zip code income was associated with lung transplant (HR, 1.22 [95% CI, 1.13-1.31] per $10,000 increase) but not death (HR, 0.99 [95% CI, 0.94-1.04] per $10,000 increase). Enrollment at a center with a lung transplant program was associated with lung transplant (HR, 4.31 [95% CI, 1.76-10.54]) but not death (HR, 0.99 [95% CI, 0.69-1.43]). Oxygen use with activity was associated with both lung transplant and death, but more strongly with lung transplant. A higher number of comorbidities was associated with an increased likelihood of death but not lung transplant. Conclusions: For patients in the Idiopathic Pulmonary Fibrosis Prospective Outcomes Registry, median zip code income and access to a lung transplant center differentially impact the risk of lung transplant compared with death, regardless of disease severity measures or other transplant eligibility factors. Interventions are needed to mitigate inequalities in lung transplantation based on socioeconomic status. Clinical trial registered with www.clinicaltrials.gov (NCT01915511).