[Optimal screening tool for thoracic diseases: chest X ray or CT?]

There are good reasons to believe that screening of lung parenchymal diseases by CT is superior to chest radiographs. Nevertheless, conventional chest radiography often remains the first examination performed for evaluation of thoracic diseases and, irrespective of clinical indication, it plays an important role in screening procedures. The interpretation methodology of a chest radiograph in a screening condition is reviewed. Specific attention to poor detectability zones is emphasized and a check-list is proposed, mainly to reduce the risk of overlooking lesions. Techniques, indications and respective diagnostic values for both chest radiography and CT scan are analyzed and applied to the screening of lung cancer, asbestos exposure and tuberculosis.