Screening examinations are tests performed to find disease before symptoms begin. The goal of screening is to detect disease at its earliest and most treatable stage. In order to be widely accepted and recommended by medical practitioners, a screening program must meet a number of criteria, including reducing the number of deaths from the given disease.

Screening tests may include laboratory tests to check blood and other fluids, genetic tests that look for inherited genetic markers linked to disease, and imaging tests that produce pictures of the inside of the body. These tests are typically available to the general population; however, an individual's needs for a specific screening test are based on factors such as age, gender and family history.

In lung cancer screening, individuals who have a high risk of developing lung cancer but no signs or symptoms of the disease undergo low-dose computed tomography (LDCT) scanning of the chest.

LDCT is a unique CT scan technique that combines special x-ray equipment with sophisticated computers to produce multiple, cross-sectional images or pictures of the inside of the body. LDCT produces images of sufficient quality to detect many abnormalities while using up to 90 percent less ionizing radiation than a conventional chest CT scan.

In the past, two other tests have been used to check for lung cancer: chest x-ray and sputum cytology. A chest x-ray makes images of the heart, lungs, airways, blood vessels and the bones of the spine and chest. X-rays are the oldest and most frequently used form of medical imaging. Sputum cytology is a laboratory test in which a sample of sputum (mucus that is coughed up from the lungs) is viewed under a microscope to check for cancer cells. However, the use of chest x-ray and sputum cytology, individually or in combination, has not resulted in a decreased risk of dying from lung cancer.

Lung cancer is cancer that forms in tissues of the lung, usually in the cells lining air passages.

Lung cancer is the leading cause of cancer deaths in the United States and worldwide. Approximately 85 percent of lung cancer deaths occur in current or former cigarette smokers.

The most common type is non-small cell lung cancer. The type of cancer diagnosed is based on how the cells look under a microscope.

Lung cancer that is detected early — before spreading to other areas of the body — is more often successfully treated. Unfortunately, when lung cancer is diagnosed, occasionally the disease has already spread outside the lung.