Validation of a post-transplant chronic lung allograft dysfunction classification system.

Background: Long-term survival after lung transplantation (LTx) is hampered by chronic lung allograft dysfunction (CLAD). Our study evaluated the prevalence and prognostic importance of obstructive and restrictive CLAD phenotypes, with or without an identifiable underlying cause, to validate the recently proposed classification system for CLAD.

Methods: Data for patients who underwent LTx between 2004 and 2015 with a minimal survival of 180 days post-LTx were retrospectively collected. Double LTx patients with CLAD (defined as a persistent forced expiratory volume in 1 second decline of ≥ 20% compared with baseline) were subsequently classified according to obstructive (forced expiratory volume in 1 second /forced vital capacity [FVC] < 70%, total lung capacity > 90%, and FVC > 80%) or restrictive (total lung capacity ≤ 90% or FVC ≤ 80%) pulmonary function and to the presence of an unknown (bronchiolitis obliterans syndrome [BOS]/restrictive allograft syndrome [RAS]) or known (non-BOS/non-RAS) underlying cause.

Results: After a median of 3.2 years, CLAD developed in 39% of double LTx patients (n = 219), of which 20% (n = 43) had an identifiable cause. Survival was worse in patients with restrictive CLAD (26%) compared with obstructive CLAD (64%; p < 0.0001). Non-BOS patients suffered from inferior survival compared with BOS patients (p = 0.0016), whereas there was no significant difference in survival between RAS and non-RAS (p = 0.17). Patients who evolved from an obstructive (BOS) to a restrictive (RAS) phenotype (10%) experienced better survival than RAS patients and a worse outcome compared with BOS patients (p < 0.0001).

Conclusions: Given the differences in outcome, accurate diagnosis of CLAD phenotypes is important, because this helps to inform patients about their prognosis, to reveal underlying pathogenesis, to identify homogenous patient populations for clinical trials, and to guide future therapeutic approaches.