Interstitial lung diseases (ILDs) are a diverse group of inflammatory and fibrotic disorders with similar manifestations. However, accurate classification and diagnosis of the ILD subtype is required so that patients receive adequate treatment.
Researchers at the Iuliu Hatieganu University of Medicine and Pharmacy, in Romania, described particular clinical features that are characteristic of each subtype of ILD, focusing particularly on idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP). The study, “State of the art in the diagnosis and management of interstitial lung disease,” was published in Clujul Medical.
The main ILD categories include ILD related to environmental exposures, connective tissue disease (CTD)-related ILD, sarcoidosis, and idiopathic interstitial pneumonias (IIPs) when IPF and NSIP are included.
It is important to distinguish idiopathic NSIP from IPF because of considerable distinct prognosis. In fact, NSIP has a 5-year survival of approximately 80% while IPF’s 5-year survival rate drops to 30%.
IPF, characterized by the morphologic pattern of usual interstitial pneumonia (UIP), is a chronic disease that highly impairs functional status and quality of life. Despite recent advances in understanding the disease development, no current therapies improve patient respiratory symptoms or functional status.
Current diagnostic criteria for IPF include exclusion of other known causes of ILD, presence of a UIP pattern on high-resolution computed tomography (HRCT) scans in patients who were not subjected to surgical lung biopsy, and specific combinations of HRCT and lung biopsy patterns in patients who underwent lung biopsy. The sensitivity and specificity for the diagnosis of IPF ranges from 60% to 80%, even when assessed by expert clinicians and radiologists.
NSIP is characterized by expansion of the alveolar walls caused by inflammation or fibrosis. It may be idiopathic (of unknown cause), but it mostly occurs in association with CTD and its clinical manifestations can range from a predominant inflammatory process to the more common predominant fibrosis. Approximately 50% of NSIP cases are missed when a biopsy is not performed.
The clinical manifestations of both IPF and NSIP are similar. Patients report shortness of breath and cough, and show respiratory sounds on auscultatory examination. Other common symptoms include fatigue, anorexia, and weight loss.
In the recent study, researchers suggest that patients should have a thorough history examination and other functional, physiological, and radiological tests to further investigate.
The six minute walk test (6MWT) reflects the functional capacity of IPF patients, and is often used to assess changes in disease status over time. HRCTs are proven reliable to diagnose UIP in IPF patients, but their ability to diagnose NSIP patients proves more challenging.
Biochemical analysis and pulmonary function tests may also prove helpful in distinguishing IPF from NSIP patients, as the impaired gas exchange in IPF patients may be identified through arterial saturation. Additionally, the tests can be used to provide an estimate of patient prognosis and disease progression by measuring proteins associated with adverse outcome.
Despite some controversial data, analysing respiratory secretions through a bronchoalveolar lavage may also help in the proper diagnosis of NSIP versus IPF.
A surgical lung biopsy can be made when physicians cannot diagnosed the patient based on the available information, though the procedure increased complications and postoperative mortality.
The study shows that patients with ILDs must be subjected to a number of tests, involving experts from many medical fields, for adequate and consensus diagnosis.