IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH TO DIAGNOSIS 2005-12-16¢  Idiopathic Pulmonary

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  • IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH

    TO DIAGNOSIS

    Sponsored by

    M O N O G R A P H

  • General Information 2

    Idiopathic Pulmonary Fibrosis: A Systematic Approach to Diagnosis 4 Charlie Strange, MD Professor of Pulmonary Medicine Division of Pulmonary and Critical Care Medicine Medical University of South Carolina Charleston, South Carolina

    References 18

    Contents 1

    IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH TO DIAGNOSIS

    CONTENTS

  • NEEDS STATEMENT Idiopathic pulmonary fibrosis (IPF) is a debilitating disease for which there is no known cause or cure. Progressive scarring or fibrosis of the lungs occurs, gradually interfering with a patient’s ability to breathe and ultimately resulting in death. Recent studies have identified that approximately 80,000 individuals suffer from IPF in the United States and an estimated 30,000 new cases develop each year. IPF is often misdiagnosed or diagnosed at an advanced stage in the disease, since it may mimic other diseases. Education to enhance physician awareness and assist in the early recognition of IPF is essential to improving overall patient care.

    LEARNING OBJECTIVES After completing this monograph, the participant will be able to: • Differentiate idiopathic pulmonary fibrosis (IPF) from other interstitial lung diseases (ILDs) • Formulate a higher index of suspicion for the early recognition of IPF • Summarize the clinical, radiographic, and pathologic tools used to identify IPF • Diagnose IPF earlier and with greater accuracy, improving patient outcomes

    INTENDED AUDIENCE This educational activity is intended for pulmonologists, pathologists, radiologists, and primary care physicians.

    METHOD OF PARTICIPATION This monograph should take approximately 1 hour to complete. The participant should, in order, read the objectives and monograph.

    DISCLAIMER The content and views presented in this educational activity are those of the author and do not necessarily reflect those of The France Foundation. This material is prepared based upon a review of multiple sources of information, but it is not exhaustive of the subject matter. Therefore, health care professionals and other individuals should review and consider other publications and materials on the subject matter before relying solely upon the information contained within this educational activity.

    IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH TO DIAGNOSIS

    2 General Information

  • FACULTY MEMBER Charlie Strange, MD Professor of Pulmonary Medicine Division of Pulmonary and Critical Care Medicine Medical University of South Carolina Charleston, South Carolina

    General Information 3

  • INTRODUCTION

    Idiopathic pulmonary fibrosis (IPF) is a chronic and often fatal lung disease characterized by progressive fibroproliferation, destruction of the alveolar architecture, and a relentless decline in pulmonary function. It affects more than 80,000 men and women in the United States, and approximately 30,000 new cases are diagnosed each year.

    The diagnosis of IPF represents a significant challenge for the clinician. The earliest clinical signs of the disease, which include a gradual onset of worsening dyspnea and a chronic nonproductive cough, are rather nonspecific and indistinguishable from those associated with several common diseases, including a number of pulmonary, cardiac, connective tissue, and vascular disorders. Moreover, the absence of reliable biomarkers or specific diagnostic tests further complicates the diagnostic process.

    As a result of these challenges, the diagnosis of IPF is often either missed or delayed until it has reached an advanced stage. In a recent prospective study of 238 patients with IPF, King and colleagues reported that the median duration of illness prior to diagnosis was 24 months (range 12–46 months).1 In light of emerging evidence suggesting that early intervention may improve patient outcomes, there is a critical need to provide physicians with practical, comprehensive continuing education aimed at facilitating the early and accurate diagnosis of IPF.

    The following pages outline a detailed approach to the diagnosis of IPF, highlighting the key elements of the clinical, radiographic, and pathologic evaluation of patients with suspected interstitial lung disease. The goal of the monograph is to provide a scientifically based, yet practical approach to the early and accurate diagnosis of IPF.

    DEFINITION OF IDIOPATHIC PULMONARY FIBROSIS

    In 2000, the American Thoracic Society (ATS) and the European Respiratory Society (ERS) published an international consensus statement that defined idiopathic pulmonary fibrosis as a specific form of chronic fibrosing interstitial pneumonia limited to the lung and associated with the histologic appearance of usual interstitial pneumonia (UIP).2 The hallmark features of the UIP include dense peripheral fibrosis, scattered foci of fibroblast proliferation, microscopic honeycombing, and a temporally heterogeneous pattern (alternating areas of fibrosis adjacent to normal lung tissue).

    IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH TO DIAGNOSIS

    4 Idiopathic Pulmonary Fibrosis: A Systematic Approach to Diagnosis

    IDIOPATHIC PULMONARY FIBROSIS: A SYSTEMATIC APPROACH TO DIAGNOSIS

  • Idiopathic Pulmonary Fibrosis: A Systematic Approach to Diagnosis 5

    In 2002, the ATS and ERS published an additional international consensus statement that provided a uniform classification system for the various idiopathic interstitial pneumonias, each of which has a reasonably characteristic clinical/radiologic/histologic pattern (Figure 1).3

    FIGURE 1. IDIOPATHIC INTERSTITIAL PNEUMONIAS

    According to the 2000 ATS/ERS statement, idiopathic pulmonary fibrosis is a diagnosis of exclusion. Even when a surgical lung biopsy reveals a histopathologic pattern of UIP, a definitive diagnosis requires the exclusion of other known causes of interstitial lung disease, including collagen vascular disease, drug toxicity, and various environmental exposures (Table 1).2

    TABLE 1. DEFINITIVE DIAGNOSIS OF IPF IN THE PRESENCE OF UIP ON LUNG BIOPSY

    1. Exclusion of other known causes of interstitial lung diseases, such as drug toxicities, environmental exposures, and collagen vascular diseases

    2. Abnormal pulmonary function studies that include evidence of restrictive disease (decreased VC, increased FEV1/FVC) and/or impaired gas exchange (increased AaPO2 difference, decreased DLco)

    3. Specific abnormalities on conventional chest radiographs or high-resolution computed tomography (HRCT) scans

    In some patients, surgical lung biopsy is unobtainable or simply not necessary to diagnose IPF, and a combination of clinical presentation and noninvasive evaluations can strongly suggest a diagnosis of IPF. The consensus statement further describes 4 major and 4 minor criteria, and suggests that the presence of all 4 major and 3 of the 4 minor criteria significantly increases the likelihood of a correct diagnosis of IPF (see Table 2).2

    Histologic Pattern

    Usual interstitial pneumonia (UIP) Nonspecific interstitial pneumonia (NSIP) Organizing pneumonia (OP) Diffuse alveolar damage (DAD) Respiratory bronchiolitis (RB)

    Desquamative interstitial pneumonia (DIP) Lymphoid interstitial pneumonia (LIP)

    Diagnosis

    Idiopathic pulmonary fibrosis (IPF) Nonspecific interstitial pneumonia (NSIP) Cryptogenic organizing pneumonia (COP) Acute interstitial pneumonia (AIP) Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) Desquamative interstitial pneumonia (DIP) Lymphoid interstitial pneumonia (LIP)

  • TABLE 2. CRITERIA FOR DIAGNOSING IPF IN THE ABSENCE OF LUNG BIOPSY

    Major Criteria • Exclusion of other known causes of interstitial lung disease, such as drug toxicities,

    environmental exposures, and connective tissue diseases • Abnormal pulmonary function studies exhibiting restrictive disease and impaired gas

    exchange • Bibasilar reticular pattern with a minimum of ground glass opacities on HRCT • Transbronchial biopsy or bronchoalveolar lavage (BAL) without features that support

    an alternate diagnosis

    Minor Criteria • Age > 50 years • Insidious onset of otherwise unexplained dyspnea on exertion • Duration of illness ≥ 3 months • Bibasilar, inspiratory crackles (dry or “Velcro” type)

    Many factors must be weighed before making the decision to perform a surgical lung biopsy. Raghu and colleagues demonstrated that a thorough clinical assessment and HRCT are both associated with a very high specificity (97% and 90%, respectively) but a relatively low sensitivity (62% and 78.5%, respectively) for the diagnosis of new-onset IPF.4 Thus, the investigators concluded that not all patients with suspected IPF require a surgical biopsy for accurate diagnosis, but when the diagnosis is unclear, a biopsy is indicated.

    MEDICAL HISTORY

    The evaluation of a patient with suspected IPF begins with a thorough medical history. Patients may note a variety of symptoms. The most prominent is a dry cough and shortness of breath on exertion.5 Cough is often of insidious onset, occurring in paroxysms that are refractory to treatment with antitussive agents, while dyspnea is the most disabling of symptoms, progressive in nature, and is usually present for greater than 6 months prior to initial presentation. On the other hand, low-grade fevers, weight loss, malaise, fatigue, myalgias, and other constitutional symptoms are infrequent in patients with IPF, and their existence and re