Clinical and Functional Characteristics of Patients with Unclassifiable Interstitial Lung Disease (uILD): Long-Term Follow-Up Data from European IPF Registry (eurIPFreg).

Ekaterina Krauss,Mustapha El-Guelai,Joern Pons-Kuehnemann,Bruno Crestani,Werner Seeger,Ludger Fink,Martina Korfei,Poornima Mahavadi,Silke Tello,Raphael W Majeed,Ruth C Dartsch,Andreas Breithecker,Andreas Guenther,Mark Stoehr

doi:10.3390/jcm9082499

Abstract

(1) Aim of the study: In spite of extensive research, up to 20% of interstitial lung diseases (ILD) patients cannot be safely classified. We analyzed clinical features, progression factors, and outcomes of unclassifiable ILD (uILD). (2) Methods: A total of 140 uILD subjects from the University of Giessen and Marburg Lung Center (UGMLC) were recruited between 11/2009 and 01/2019 into the European Registry for idiopathic pulmonary fibrosis (eurIPFreg) and followed until 01/2020. The diagnosis of uILD was applied only when a conclusive diagnosis could not be reached with certainty. (3) Results: In 46.4% of the patients, the uILD diagnosis was due to conflicting clinical, radiological, and pathological data. By applying the diagnostic criteria of usual interstitial pneumonia (UIP) based on computed tomography (CT), published by the Fleischner Society, 22.2% of the patients displayed a typical UIP pattern. We also showed that forced vital capacity (FVC) at baseline (p = 0.008), annual FVC decline ≥10% (p < 0.0001), smoking (p = 0.033), and a diffusing capacity of the lung for carbon monoxide (DLco) ≤55% of predicted value at baseline (p < 0.0001) were significantly associated with progressive disease. (4) Conclusions: The most important prognostic factors in uILD are baseline level and decline in lung function and smoking. The use of Fleischner diagnostic criteria allows further differentiation and accurate diagnosis.

Highlights

Interstitial lung diseases (ILD) are a heterogeneous group of parenchymal fibrosing lung diseases characterized by varying degrees of inflammation and scarring [1]
Some of the interstitial lung diseases (ILD) entities are associated with a progressive fibrosing phenotype, being clinically characterized by progressive respiratory symptoms, a faster decline of lung function, limited response to antifibrotic or immunomodulatory therapies, decreased health-related quality of life (HRQoL), and as a consequence, early death [2,3]
This term was introduced in the American Thoracic Society/European Respiratory Society (ATS/ERS) Consensus Classification of the interstitial pneumonias (IIPs) in 2002, as a description of an ILD subgroup that cannot be classified within the confines of the current diagnostic framework [12]

Summary

Introduction

Interstitial lung diseases (ILD) are a heterogeneous group of parenchymal fibrosing lung diseases characterized by varying degrees of inflammation and scarring [1]. In up to 20% of ILD patients, a specific diagnosis cannot be defined, even after thorough MDT discussion. In such a situation, the disease would be labeled as an “unclassifiable ILD” (uILD) [11]. The disease would be labeled as an “unclassifiable ILD” (uILD) [11] This term was introduced in the American Thoracic Society/European Respiratory Society (ATS/ERS) Consensus Classification of the IIPs in 2002, as a description of an ILD subgroup that (at least temporarily) cannot be classified within the confines of the current diagnostic framework [12]. A recent International Working Group suggested that uILD should be defined by the absence of a leading diagnosis that is considered more likely than not (after MDT discussion of all available information) [13]

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