The Keys to Making a Confident Diagnosis of IPF

Abstract

Diffuse parenchymal lung diseases (DPLDs) are characterized by injury primarily to the interstitium of the lung, but may involve alveolar spaces, airways, and vessels (American Thoracic Society/European Respiratory Society. Am J Respir Crit Care Med 165(2):277–304, 2002). Many DPLDs are idiopathic (referred to as idiopathic interstitial pneumonias, or IIPs), but DPLD can develop secondary to other factors, including connective tissue disease (CTD), environmental exposures, and drugs/toxins (American Thoracic Society/European Respiratory Society. Am J Respir Crit Care Med 165(2):277–304, 2002). The IIPs include idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia (COP), respiratory bronchiolitis interstitial lung disease (RB-ILD), acute interstitial pneumonia (AIP), lymphocytic interstitial pneumonia (LIP), and desquamative interstitial pneumonia (DIP) (American Thoracic Society/European Respiratory Society. Am J Respir Crit Care Med 165(2):277–304, 2002). There is significant overlap in the clinical features of the IIPs, including chronic dyspnea, interstitial changes on imaging studies, reduction in lung volumes, and impairment in diffusion capacity (DLCO) (American Thoracic Society/European Respiratory Society. Am J Respir Crit Care Med 165(2):277–304, 2002). Distinct radiographic and histopathological features can distinguish between the clinical entities, and establishing an accurate diagnosis is critical to determining treatment and understanding prognosis (Flaherty et al. Eur Respir J 19(2):275–83, 2002; Bjoraker et al. Am J Respir Crit Care Med 157(1):199–203, 1998).Of the over 150 recognized types of DPLDs, IPF is the most common and has the worst prognosis (Flaherty et al. Eur Respir J 19(2):275–83, 2002; Bjoraker et al. Am J Respir Crit Care Med 157(1):199–203, 1998). IPF is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown etiology that occurs primarily in older adults, is limited to the lungs, and is associated with a histopathological and/or radiologic pattern of usual interstitial pneumonia (UIP) (Raghu et al. Am J Respir Crit Care Med 183(6):788–824, 2011). As outlined in the ATS/ERS 2011 consensus statement, the diagnosis requires the exclusion of known causes of DPLD and the presence of a UIP pattern on high-resolution computed tomography (HRCT) or surgical lung biopsy (SLB) (Raghu et al. Am J Respir Crit Care Med 174(7):810–6, 2006). The incidence and prevalence of IPF increase with age, and the diagnosis should be considered in older adult patients who present with nonproductive cough, dyspnea, and bibasilar crackles (Raghu et al. Am J Respir Crit Care Med 174(7):810–6, 2006; Douglas et al. Am J Respir Crit Care Med 161(4 Pt 1):1172–8, 2000; Fell et al. Am J Respir Crit Care Med 181(8):832–7, 2010).This chapter reviews the key historical, physiologic, radiographic, and histopathological features that are key to establishing a confident diagnosis of IPF.KeywordsPulmonary fibrosisPhenotypeMimicsMultidisciplinaryConfidence