Labs and Tests

Many tests are needed to help monitor a patient with cystic fibrosis.

The Cystic Fibrosis Foundation patient care guidelines state that CF patients should be seen at least quarterly. These guidelines also recommend that laboratory tests are evaluated at least yearly.

There are numerous reasons these labs are done:

  • To rule out infection
  • Assess iron level
  • Check for CF liver disease
  • Make sure fat soluble vitamin levels are adequate
  • Check nutritional status
  • Check for CF related diabetes
  • Make sure bleeding times are appropriate
  • If someone has CF related diabetes, checking blood hemoglobin A1c and urine microalbumin is essential to avoid diabetes complications.

The importance of annual labs in your health and well being cannot be overstated!

In any patient with CF, lung infections, inflammation, and scarring can occur early in life. These lung problems may or may not create symptoms, and may or may not show in pulmonary function testing. The chest x-ray allows the team to see if there is any damage, to establish a baseline allowing comparison of subsequent chest x-rays, and to provide a diagnostic tool. The CF team also can use these results to help determine the need for inhaled medications, such as pulmozyme or hypertonic saline.
The chest X-ray is usually performed with the patient standing.

High Resolution Computerized Tomography of the Chest (HRCT)

The HRCT is used to see if structural damage has occurred in the lungs. A baseline is also established for comparision. The HRCT is sensitive enough to find small areas of mucus plugging, inflammation and early damage in the lungs.

The HRCT is performed with the patient lying on his or her back while a special X-ray machine rotates around the body. The HRCT takes pictures of thin sections of the lungs. Wear comfortable clothes, and leave jewelry at home. You may be asked to hold your breath to get the clearest picture.

During each clinical visit, a hand held device called a spirometer will measure a FVC (forced vital capacity) and a FEV1 (forced expiratory volume in one second).

The FVC measures the total amount of air a person can breathe out forcefully after one deep breath. The FEV1 measures the amount of air forced out in the first second of the FVC.

With the results of these 2 tests,  a clinician is able to tell if there are any lung volume abnormalities and which therapies can help to improve them.  The respiratory therapist will provide you with a copy of the PFT performed in clinic.  From time to time, you may also receive a copy of FEV1 results from the registry.

Actual documentation of testing begins around age 6.  The results are based on the child’s age, sex, height, and weight.

The child may be introduced to the equipment and the deep breathing manuevers as early as 5, with noisemakers to blow into.

Formal PFTs are done yearly in the hospital PFT lab, for more complete testing and information.

For questions about PFTs, contact your clinic respiratory therapist or your CF physician.

Pulse oximetry is used to estimate the amount of oxygen in the blood. This measurement is taken by shining specific wave lengths of light through one side of an appendage and measuring the amount that makes it through to the other side. A computer then runs this information through algorithms based on study data and calculates an estimated percentage. Health care providers typically refer to this percentage as an oxygen saturation or sat for short. Technically, the sat is the percentage of hemoglobin in the red blood cells that is combined with oxygen. Normal levels  over 90 percent when breathing room air. A sat lower than 90 percent can place a great strain on the body. In order to deliver as much oxygen as possible  to living cells, the heart, lungs, and blood vessels must work much harder than usual. Over time, this extra work can cause permanent injury.

Often, an inadequate oxygen level in the blood is caused by a problem with the lungs. If lung tissue is damaged, inflamed, or blocked off, your body cannot capture enough oxygen from the air you breath.

At the CF clinic we check oxygen saturation as part of your routine checkup.

What are they?

At each clinic, the respiratory therapist will obtain a sputum sample or a throat culture to test for respiratory infection. You will be asked to cough into a sterile cup for the sputum sample.

If you can not cough out a sample, the respiratory therapist will swab the back of your throat with a soft, flexible Q tip.


It is best if you have not had anything to eat or drink for at least 2 hours before having a throat culture or sputum sample. Please do not use mouthwash before coming to clinic. You may be asked to rinse your mouth out with water before the sample. Having a throat culture may cause some mild discomfort or gagging.

Per St. Luke’s patient identification policy, your sputum sample or throat culture will be marked as yours in front of you.

When do we get the results?

The sample is sent to the lab. The sample is then placed on a special plate that enables growth of certain bacteria if they are present in the sputum. The results come back in 3 to 5 days. If there is a new infection present, you will be contacted by the doctor or nurse coordinator and prescribed antibiotics.


Other common tests in CF include:  Dexa Scan for bone density, sleep study, audiology (hearing tests), ophthalmology referral (for CFRD)

If you have any questions about lab tests, please contact your CF physician or the CF Center of Idaho nurse coordinator, Mary Nelsen. Mary can be reached at 381-7092.