There are many different laboratory tests for diagnosing cystic fibrosis and monitoring the progression of cystic fibrosis symptoms. That said, most cystic fibrosis cases are first diagnosed through universal genetic testing at birth. A positive genetic test is usually followed up by a sweat test, which is highly reliable for diagnosing cystic fibrosis. Moreover, lung function in infants with cystic fibrosis tends to be normal. Therefore, a lung X-ray early in development would not typically reveal any concerns [source: NHLBI].

Chest X-rays are generally used to determine lung function throughout the life of a person with cystic fibrosis. Early detection of diminished lung function or inflammation is essential for effective intervention before irreversible lung damage occurs. An X-ray is a painless test that quickly and effectively determines inflammation of the lungs, bronchial tubes and sinuses. Your cystic fibrosis doctor may also order a computerized tomography (CT) scan. A CT scan produces more detailed imagines of the lungs, leading to a more accurate assessment of lung function. Finally, your doctor may also order a magnetic resonance imagining (MRI) test of the lungs, which also produces a more detailed image of internal organs [source: Mayo Clinic]. Typically, a chest X-ray is combined with a lung function test. A lung function test determines the size of your lungs, how much air you can hold, how quickly you can breathe, and your lung efficiency for delivering oxygen into your bloodstream [source: NHLBI].

A recent study found that high-resolution computed tomography (HRCT), a version of a CT scan, is the most useful tool for identifying early lung problems in cystic fibrosis patients. HRCT can detect even mild respiratory symptoms in the lungs [source: Santamaria et al.].