Reply to Nett et al.: Collecting Occupational Exposure Data Would Strengthen Idiopathic Pulmonary Fibrosis Registries.

From the Authors:

We appreciate the perspective shared by Nett and colleagues regarding the potential utility of registries to assess the contribution of occupational and environmental exposures to the development and outcomes of idiopathic pulmonary fibrosis (IPF). We agree that exposures constitute an important source of risk for patients with IPF, and also perhaps for susceptible individuals at risk for developing clinically overt fibrosis. In this regard, expanding occupational assessments to include cohorts of patients with interstitial lung abnormalities may facilitate easier identification of exposure relationships through the sheer proportions of patients with interstitial lung abnormalities compared with narrowly defined IPF.

Measuring exposure relationships with IPF poses several challenges, which unfortunately have not yet been overcome. However, our plea for future IPF registries to consider investigating novel aspects of pulmonary fibrosis certainly accords with the idea of more in-depth occupational assessments (1). Given the small numbers of patients in any given occupation, collaborations among registries, as has been proposed for several European registries, may enhance the likelihood of identifying culpable exposures (2).

The absence of validated exposure tools that can be completed by patients and harried clinicians is a current difficulty. There are several other barriers to identifying occupational relationships with pulmonary fibrosis, many of which are not easily addressed with registries that focus on disease manifestations and patient-centered outcomes. These barriers include nagging issues regarding the aggressiveness of exposure assessments, poor recall in an elderly population, latency, the complex effects of gene–environment interactions, and potentially modifying effects of evolving environmental controls in a disease that typically requires many years to fully develop.

IPF is widely regarded to be due to deranged wound-healing responses to epithelial cell injury. The label “idiopathic” is probably no longer appropriate, as a variety of nonoccupational lung exposures have been linked to the development and prognosis of IPF, including tobacco use, gastroesophageal reflux, and air quality (3, 4). It is unsurprising, therefore, that any occupation that involves the generation of respirable particles may be a risk factor for IPF. Epidemiologic data are indeed necessary to help clinicians and policy-makers identify which particle types are likely to injure the epithelium the most, driving the progression of fibrosis. Moreover, further elucidation of gene–environment relationships in pulmonary fibrosis may eventually allow for better screening of at-risk workers.

We welcome continued dialogue among pulmonologists, epidemiologists, industrial hygienists, occupational medicine specialists, preclinical scientists, and patients. We agree that collaboration among all relevant parties will be instrumental in further refinement of historical and future IPF risk factors.