Some signs, such as clubbing and crackles, are often features of advanced disease. The clinical search must consider signs of CHF in order to rule it out as a cause of the interstitial changes. It is also imperative to know the patient's immunological status and risk of acquiring certain infectious and noninfectious diseases. Another important initial step in the diagnostic approach is to review the entire series of chest x-rays to establish the degree of disease activity. The radiographic pattern also has discriminating power.
Reticular pattern is most common in lymphangitic spread, asbestosis, or scleroderma.
A miliary pattern is seen in patients with tuberculosis, histoplasmosis, or varicella pneumonia. Kerley-B lines may be seen in patients with lymphatic congestion of CHF, lymphangitic carcinomatosis, LAM, lymphoma, and post radiation lymphangiectasis. Finally a ground-glass appearance, although not specific for any particular disease, usually indicates a sign of active inflammation. The predominance of certain subgroups of cells in patients with DPLD might be helpful in the differential diagnosis. Transbronchial lung biopsy is often diagnostic in cases of sarcoidosis, lymphangitic carcinomatosis, bronchoalveolar cell carcinoma, eosinophilic pneumonia, pulmonary alveolar proteinosis, and is occasionally helpful in cases of eosinophilic granuloma, HSP, BOOP, lymphocytic interstitial pneumonitis, and amyloidosis.