Estimation of the Prevalence of Progressive Fibrosing Interstitial Lung Diseases: Systematic Literature Review and Data from a Physician Survey

Abstract

Some patients with interstitial lung diseases (ILDs) other than idiopathic pulmonary fibrosis exhibit a progressive clinical phenotype. These chronic progressive fibrosing ILDs have a variety of underlying diseases, and their prevalence is currently unknown. Here we carry out the first systematic review of literature on the prevalence of fibrosing ILDs and progressive fibrosing ILDs using data from physician surveys to estimate frequency of progression among different ILDs. We searched MEDLINE and Embase for studies assessing prevalence of ILD, individual ILDs associated with fibrosis and progressive fibrosing ILDs. These were combined with data from previously published physician surveys to obtain prevalence estimates of each chronic fibrosing ILD with a progressive phenotype and of progressive fibrosing ILDs overall. We identified 16 publications, including five reporting overall ILD prevalence, estimated at 6.3-76.0 per 100,000 people in Europe (four studies) and 74.3 per 100,000 in the USA (one study). In total, 13-40% of ILDs were estimated to develop a progressive fibrosing phenotype, with overall prevalence estimates for progressive fibrosing ILDs of 2.2-20.0 per 100,000 in Europe and 28.0 per 100,000 in the USA. Prevalence estimates for individual progressive fibrosing ILDs varied up to 16.7 per 100,000 people. These conditions represent a sizeable fraction of chronic respiratory disorders and have a high unmet need.

Keywords: Epidemiology; Fibrosis; Interstitial lung disease; Prevalence; Progressive.

Fig. 1

Conceptual diagram of prevalence estimation for progressive fibrosing ILDs [5]. Figure is not to scale. “Autoimmune ILDs” includes RA-ILD, SSc-ILD, PM-ILD, DM-ILD, Sjögren’s-ILD, SLE-ILD, CTD-ILD and MCTD-ILD; “Non-IPF IIPs” includes iNSIP and unclassifiable IIP; “Environmental ILDs” includes asbestosis, silicosis and coal worker’s pneumonitis. CTD-ILD connective tissue disease-associated interstitial lung disease, DM-ILD dermatomyositis-associated interstitial lung disease, HP hypersensitivity pneumonitis, IIP idiopathic interstitial pneumonia, ILD interstitial lung disease, iNSIP idiopathic non-specific interstitial pneumonia, IPF idiopathic pulmonary fibrosis, MCTD-ILD mixed connective tissue disease-associated interstitial lung disease, PM-ILD polymyositis-associated interstitial lung disease, RA-ILD rheumatoid arthritis-associated interstitial lung disease, SLE-ILD systemic lupus erythematosus-associated interstitial lung disease, SSc-ILD systemic sclerosis-associated interstitial lung disease. Adapted with permission of the © ERS 2020. European Respiratory Journal 51 (5) 1800692; https://doi.org/10.1183/13993003.00692-2018 Published 17 May 2018

Fig. 2

Prevalence of ILD in Europe and the USA. ^aAs calculated from [21]. ^bAs reported by [30]. ^cAs reported by [26]. ^dAs reported by [1]. ^eAs recalculated from [24], using the total population as the denominator. ILD interstitial lung disease

Fig. 3

Prevalence of fibrosing ILDs in Europe and the USA. ^aAs reported by or calculated from [2, 24, 26]. ^bAs reported by or calculated from [24, 26, 30]. ^cAs reported by or calculated from [2, 21, 24, 26, 30]. ^dAs reported by or calculated from [24, 26]. ^eAs reported by or calculated from [2, 21, 24, 26, 30]. ^fAs reported by [21, 26]. ^gAs reported by [16, 21, 26]. ^hAs reported by or calculated from [24, 30]. ⁱAs reported by or calculated from [, –26, 30]. CTD-ILD connective tissue disease-associated interstitial lung disease, DM-ILD dermatomyositis-associated interstitial lung disease, HP hypersensitivity pneumonitis, IIP idiopathic interstitial pneumonia, ILD interstitial lung disease, iNSIP idiopathic non-specific interstitial pneumonia, IPF idiopathic pulmonary fibrosis, MCTD-ILD mixed connective tissue disease-associated interstitial lung disease, PM-ILD polymyositis-associated interstitial lung disease, RA-ILD rheumatoid arthritis-associated interstitial lung disease, SLE-ILD systemic lupus erythematosus-associated interstitial lung disease, SSc-ILD systemic sclerosis-associated interstitial lung disease