Cystic Fibrosis - Diagnosis

A number of factors may suggest that a child be tested for cystic fibrosis. The presence of any of the described symptoms may lead to such tests. These symptoms include gastrointestinal or respiratory problems that do not disappear, and the presence of salty sweat. A baby born with meconium ileus will be tested before leaving the hospital. Some hospitals now require routine CF screening for newborn babies.

The easiest and most accurate test for CF is a sweat test. A sample of an individual's sweat is collected. The sample is then tested for salt content. If the salt content is 1.5 to 2 times greater than normal, the individual probably has CF.

Genetic testing can also be used to diagnose CF. A small blood or tissue sample is taken from the patient. The sample can then be analyzed to determine whether the individual's CFTR gene is normal or defective. The presence of a defective gene means that the person has cystic fibrosis.

Screening of newborn babies is done with a test known as the IRT test. This test measures the amount of a particular chemical in the blood known as immunoreactive trypsinogen (pronounced trip-SIN-uh-juhn). Babies with CF have a high level of this chemical.