Common Medical Tests for Cystic Fibrosis Diagnosis and Monitoring

The Cystic Fibrosis (CF) Center provides outpatient testing and services to pediatric, adolescent, and adult patients with CF. Below are some of the tests used to diagnose and monitor the disease.

Sweat Testing

People with CF have a higher concentration of salt in their sweat. The sweat test is a painless procedure and can be performed on individuals of any age. Doctors apply a chemical and light electrical stimulation to the skin to induce sweating. Then they collect sweat either on a filter paper, a piece of gauze, or in a plastic receptacle, and analyze the results. The sweat test has been the gold standard for diagnosing cystic fibrosis (CF) for more than 40 years.

Genetic Testing

CF is a genetic disease caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. There are more than 1,800 known mutations of that gene, but only some of these cause CF. Different mutations cause different effects, and with advances in current therapies, knowing the exact kind of mutation can help identify more effective treatments. In addition to the sweat test, genetic testing for CF is now standard and recommended. We offer a 139-mutation panel for enhanced screening as well as full gene sequencing for suspected diagnoses.

Pancreatic Function Testing

Approximately 85 percent of all CF patients have “pancreatic insufficiency,” in which the pancreas does not produce enough of the enzymes that aid in digestion. This condition may affect nutrition and growth. It can be easily treated with enzyme therapy. The “fecal elastase” test is a stool test that can determine the level of pancreatic function.


Bloodwork enables physicians to check blood counts, electrolytes, liver function, clotting times, fat soluble vitamin levels, glucose tolerance, liver function, lipid panel, and immunoglobulins.

Sputum Cultures

Sputum is mucus from the lungs that is produced when you cough. It is not saliva. A sputum culture enables doctors to see what bacteria you may have and what antibiotics can be effective in fighting it. You will be asked to cough into a cup to collect the sample. Children and adults who cannot produce a sputum sample will receive a cough swab.

Oral Glucose Tolerance Test

Doctor and child - CF testsStarting at age 10, patients should have an oral glucose tolerance test (OGTT) once annually to screen for CF-related diabetes (CFRD). CFRD is common among people who have the disease, as the pancreas may have difficulty producing enough insulin. This test is usually done the same day as other annual bloodwork. Pediatric patients get annual labs and OGTT testing in our Same-Day Suite and adult patients use the outpatient labs.


A chest X-ray is recommended annually to monitor for disease progression or any abnormalities in the lungs that should be treated. From adolescence, it is recommended that people also receive a CT scan of the chest sometimes as frequently as every two years.

Pulmonary Function Testing

Pulmonary function tests (PFT) are tests that measure how well your lungs are working. PFTs are done at every clinic visit beginning at age 6. A full range of PFTs is done once a year in the hospital Pulmonary Function Lab.

Bone Mineral Density Scan

Also known as dual-energy X-ray absorptiometry (DEXA) scan, a bone mineral density scan is a test to check for the presence of osteopenia or osteoporosis. This test is done anywhere between one and five years apart, depending on the results. Normal DEXA scans do not need to be repeated for five years. When scans show abnormal results, treatment is required and the scan will be repeated within one to two years.


A bronchoscopy is a procedure in which a physician threads a thin tube with a camera and a light at the end down your throat to view your airways. If you are not responding to therapy as well as expected, are getting sick more frequently, or the doctor suspects there is unidentified bacteria in the lungs which needs treatment, a bronchoscopy may be prescribed. During a bronchoscopy, the doctor can obtain sputum cultures from deeper sections of the lungs for testing. The doctor also has an opportunity to clear mucous plugs from the lungs during the procedure.

Annual Testing

The Cystic Fibrosis Foundation recommends that people with CF have following tests every year:

  • Bloodwork
  • Bone mineral density scan
  • Full pulmonary function testing
  • Imaging
  • Oral glucose tolerance test (for non-diabetic patients 10 years and up)

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