Effect on the Prevalence of Various Diffuse Parenchymal Lung Diseases due to Paradigm Change in the Guidelines

Abstract

Background: Diffuse parenchymal lung diseases (DPLDs) have gone through various changes in nomenclature and classification since they were first described in 1868. Increasing knowledge about their etiopathogenesis has since led to several reclassifications and changes in the nomenclature. This has had a major impact on the prevalence of each interstitial lung disease (ILD) reported by the different registries worldwide. In this study, we attempted to describe the distribution of the different DPLDs in our population and reported changes in prevalence due to changing diagnostic criteria for the disease. Materials and methods:We analyzed retrospective data of 434 patients. For the initial 75 patients, ATS/ERS guidelines published in 2002 were followed in the diagnosis of the ILD (group I). In the later part of the study (359 patients), the diagnosis was based on the computed tomography (CT) patterns defined by ATS/ERS/JPS/ALAT statement on diagnosis of idiopathic pulmonary fibrosis (IPF) and updated 2013 ATS/ ERS guidelines (group II). Results: Of the 75 patients in group I, IPF was the most common diagnosis (52%) made at that time, followed by sarcoidosis and connective tissue-related ILD (CTD-ILD) with 12% each. Group II had 359 patients, with IPF again being the most commonly diagnosed ILD with 21.3%. This was followed by CTD-ILD (18.6%), sarcoid (14.7%), and idiopathic nonspecific interstitial pneumonitis (iNSIP; 13.3%). The changing guidelines have an impact on reporting of different DPLD by our multidisciplinary teamover a period of time. Though IPF was the most commonest DPLD reported among both the groups, the diagnosis of IPF had fallen by more than half in the second group. It was paralleled by an increase in the diagnosis of iNSIP and chronic hypersensitivity pneumonitis. These reported changes in the prevalence of DPLDs may reflect the better-defined criteria in the latest guidelines and a better understanding of the fibrotic ILDs other than IPF by the multidisciplinary team. Conclusions: The frequency of diagnosis of the different DPLDs has changed, following the publication of several guidelines in the last decade. It has recognized newer entities with greater clarity, such as idiopathic NSIP and interstitial pneumonia with autoimmune features.