Chronic Lung Allograft Dysfunction: Definition, Diagnostic Criteria, and Approaches to Treatment

As a consequence of observations supporting the heterogeneity within bronchiolitis obliterans syndrome (BOS), the term chronic lung allograft dysfunction (CLAD) has been proposed as an umbrella term to describe the clinical manifestations of a range of pathologic processes in the airway and parenchymal compartments of the lung allograft that lead to a significant and persistent deterioration in lung function (with or without chest radiologic changes) and occur >3 months after LTx.

The lack of a consensus definition of CLAD and how it relates to BOS has been problematic. Factors including the varied timing and reproducibility of spirometry and the frequent presence of potentially reversible conditions, such as infection, pleural effusion, or acute rejection, that subsequently fail to improve with treatment may result in lack of agreement about the presence and timing of onset of CLAD. Furthermore, some authors have used the term CLAD as a synonym for BOS, or a combination of BOS and RAS, whereas others proposed to use CLAD for every possible post-transplant decline in FEV₁.

As a consequence, the Pulmonary Council of the ISHLT assembled a group of experts to create a robust description for the term CLAD that would encompass its definition, etiology, phenotypes, pathology, treatment, and outcome. It was acknowledged that the lack of literature available on this specific topic mandated the generation of a consensus report based on expert opinion.

The primary aim of this consensus report is to standardize the nomenclature of CLAD and its clinical phenotypes to facilitate collaboration among centers investigating the pathogenesis, prevention, and treatment of CLAD.