Diagnostic approach to the patient with interstitial lung disease

Interstitial lung diseases (ILDs) consist of a heterogeneous group of parenchymal lung disorders that vary in etiology, clinicoradiologic presentation, histopathologic features, and clinical course. In approximately 50% of ILDs, the cause is unknown although the clinicopathologic syndrome may be well recognized, e.g., idiopathic pulmonary fibrosis. Clinical evaluation of patients with suspected ILD aims to identify the underlying cause or the clinicopathologic syndrome, assess prognosis, and determine the optimal management strategy. Thus, the elicited history and subsequent clinical evaluation are tailored to meet these goals in an individual patient. Although the diagnostic approach will vary depending on individual circumstances, it is useful to focus on 3 parameters in the diagnostic evaluation: clinical context, tempo of the disease process, and radiologic findings. The clinical context provides the initial set of data based on which the diagnostic possibilities can be prioritized and includes demographic and clinical data as well as the results of the initial evaluation. Although most ILDs are chronic disorders, acute presentation can be seen in several disorders such as hypersensitivity pneumonitis, acute interstitial pneumonia, and diffuse alveolar hemorrhage syndromes. Radiologic imaging, particularly high-resolution computed tomography of the chest, is very helpful in narrowing the broad differential diagnosis and guiding subsequent diagnostic steps. Each of these parameters can yield important clues in identifying the underlying clinicopathologic entity and the cause. Concise formulation of these essential parameters will facilitate the diagnostic process and lead to optimal management in patients with ILDs.