Prevalence and Incidence of Chronic Fibrosing Interstitial Lung Diseases with a Progressive Phenotype in the United States Estimated in a Large Claims Database Analysis

INTRODUCTION: Many fibrosing interstitial lung diseases (ILDs) develop a chronic progressive phenotype. While idiopathic pulmonary fibrosis, which is always progressive, is well characterized with established treatment options, the epidemiology of other chronic fibrosing ILDs with a progressive phenotype has not been widely investigated. Treatment options are limited, with a high unmet need. This claims database study estimates the incidence and prevalence of these diseases in the USA. METHODS: Diagnosis, procedure and resource utilization codes from insurance claims were used to identify patients with fibrosing ILD and those with a chronic progressive phenotype among 37,565,644 adult patients in the IBM(®) MarketScan(®) Research Database 2012–2015. Two eligible ILD claims were required for a fibrosing ILD diagnosis. Progression was defined using a novel algorithm constituted by criteria considered proxies for progression. Patients were defined as having incident (new) or existing diagnoses based on claims during a 365-day period before study entry. RESULTS: The estimated age- and sex-adjusted prevalence per 100,000 persons of fibrosing ILD (95% confidence interval) was 117.82 (116.56, 119.08) and of chronic fibrosing ILDs with a progressive phenotype was 70.30 (69.32, 71.27). The estimated adjusted incidence per 100,000 patient-years of fibrosing ILD was 51.56 (50.88, 52.24) and of chronic fibrosing ILDs with a progressive phenotype was 32.55 (32.01, 33.09). Among incident fibrosing ILD patients, 57.3% experienced progression over a median of 117 days (interquartile range 63–224), with largely comparable rates of progression among different diseases. CONCLUSIONS: Chronic fibrosing ILDs with a progressive phenotype comprise a relatively new disease construct requiring varied approaches to obtain reliable estimates of prevalence and incidence. This is the first large claims database study using real-world data to provide estimates of the prevalence and incidence of these diseases among a very large segment of the US population and could form the groundwork for future studies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12325-021-01786-8.