Collecting Occupational Exposure Data Would Strengthen Idiopathic Pulmonary Fibrosis Registries.

To the Editor:

We read with interest the article by Culver and colleagues (1), who describe the use of idiopathic pulmonary fibrosis (IPF) patient registries to capture clinically relevant data on the clinical course and impact of IPF. The authors summarize the attributes of IPF registries, including descriptions of current diagnostic and management practices and collection of biological specimens (1), but they do not discuss the role patient registries can play in the collection of occupational and environmental exposure data.

A diagnosis of IPF includes a presumption that known potential explanations have been excluded (2). The most recent diagnostic criteria for IPF recommend collection of a detailed environmental and occupational exposure history from patients who are clinically suspected of having IPF (2). Between 30,000 and 40,000 incident cases of IPF are diagnosed each year in the United States (3), and an estimated 26% of these cases are attributable to occupational exposures, including metal, silica, wood, and agricultural dusts (4).

The National Institute for Occupational Safety and Health analyzed 1999–2013 mortality data from 21 states that included supplemental employment history information and an underlying or contributing cause of death coded as International Classification of Diseases, 10th Revision J84.1 (other interstitial pulmonary diseases with fibrosis). After adjustment for age, sex, and race, IPF decedents who were employed in the engineered wood product manufacturing industry had a proportionate mortality ratio (PMR) of 2.62 (95% confidence interval, 1.58–4.09). Other industries with >100 IPF deaths and an elevated and statistically significant PMR included foundries (PMR, 1.78), offices of dentists (1.44), offices of physicians (1.36), and aerospace product and parts manufacturing (1.32) (unpublished data). These findings indicate associations between workplace exposures and IPF, but death certificate data are a lagging indicator and have poor sensitivity for identifying occupational lung diseases (5). Using IPF patient registries to capture occupation and environmental exposure data could provide more sensitive, specific, and timely data. The systematic collection of key occupational and environmental data (e.g., usual industry, occupation, and history of dust exposure) across multiple IPF registries could allow for pooled analyses to identify occupational and environmental exposures that might be contributing to the global interstitial lung disease burden.

We applaud Culver and colleagues for encouraging IPF registries to develop creative methodologies to explore specific hypotheses rather than continue to duplicate existing efforts. It is notable that not all cases of IPF are truly idiopathic, and some cases are likely attributable to occupational or environmental exposures (6). We encourage IPF registries to also collect occupational and environmental exposure data in a standardized and systematic fashion. These data could be pooled and analyzed to improve our understanding of the contribution of occupational and environmental exposures to the burden of interstitial lung disease and to inform recommendations for exposure control and medical monitoring.