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Cystic fibrosis


Cystic fibrosis is a genetic disease that mainly affects the respiratory and digestive systems. It causes secretions to become thick, interfering with the proper function of the lungs and pancreas. The disease can be mild to severe and can affect people in different ways.

It is estimated that 1 in every 2 500 children in Québec is born with cystic fibrosis.


The symptoms of cystic fibrosis and their severity can vary from person to person.

The main symptoms are:

  • persistent cough with thick secretions;
  • wheezing and shortness of breath, even serious respiratory problems;
  • poor absorption of food which can lead to:
    • poor weight gain,
    • weight loss,
    • delayed growth,
    • vitamin deficiencies;
  • recurrent respiratory tract infections, such as pneumonia, which can worsen from one time to the next;
  • intestinal disturbances such as intestinal obstruction and frequent, fatty stools;
  • fertility problems.


Cystic fibrosis is a recessive hereditary disease that is passed on to the child by two parents who carry the same defective gene. The affected person is born with the disease. To learn more, go to the page Recessive hereditary diseases transmission.

Diagnosis by sweat test

Under the Québec Neonatal Blood and Urine Screening Program, a blood sample is taken from your baby’s heel to screen for a number of diseases, including cystic fibrosis. If the result is abnormal for the disease, an additional test must be done. It is called a sweat test and will determine whether or not your child has cystic fibrosis and if follow-up is necessary.

A sweat test involves collecting a small amount of sweat from your child to measure the salt concentration. People with cystic fibrosis have a higher concentration of salt in their sweat.

Test procedure

A sweat test is done in a referral centre. It is painless and takes around 30 to 40 minutes.

The child’s sweat is collected from their arm. The steps are as follows:

  1. A device that stimulates sweating is strapped to the child’s arm and kept in place for a few minutes.
  2. The device is removed and a piece of filter paper is taped to the area stimulated.
  3. Plastic film is placed over the area to keep the arm warm and allow the sweat to collect on the filter paper for around 30 minutes. You can hold your child to comfort and reassure them and you can even breastfeed them or give them a bottle.
  4. The filter paper is removed and the staff takes 5 to 10 minutes to check if enough sweat has been collected. The arm may be a little red, but this is normal and does not hurt.
  5. The filter paper is sent to the laboratory for testing.

The test result will be available within hours. A member of the cystic fibrosis team at the referral centre will come and explain the result to you and answer all your questions.

Test results

In most cases, the sweat test confirms that the child does not have cystic fibrosis.

If the test confirms that your child has cystic fibrosis, they will receive the care they need.

If your child is a carrier, they will not require any particular follow-up. A healthy carrier is not sick and is not at risk of developing the disease.

Carrier status

In Québec, around 1 in 20 people is a cystic fibrosis carrier. A carrier has one defective gene associated with cystic fibrosis. They are not sick and are not at risk of developing the disease. To learn more about how genes are passed on, go to the page Recessive hereditary diseases transmission.

There is a chance that the sweat test comes back normal but the child does actually have the disease. It is, however, very low. A sweat test can identify around 90% of all the defective genes associated with cystic fibrosis, that is, the most common ones. Although it is very unlikely, your child might have a second defective gene that was not identified during the test. These less common defective genes that are not identified during the test often cause milder forms of the disease that appear later.

If you are worried about your child’s health or if they have frequent respiratory or digestive problems or delayed growth, talk to your doctor. They may order another assessment if necessary.

If your child’s sweat test shows that they are a carrier for the disease, you might want to find out your carrier status or that of other family members.

Parents’ carrier status

If the sweat test confirms that your child carries a defective gene for cystic fibrosis, one of the parents must necessarily carry the gene. The second parent might be carrying a defective gene for cystic fibrosis that they did not pass on to the child. Screening tests will be offered to both parents.

Carrier status of other children in the family

Your other children might also be healthy carriers. If they are healthy, additional tests will not be necessary. Later, when they are old enough to be parents and if they want to, they can be seen in medical genetics to find out if they carry the defective gene.


There is no cure for people who have cystic fibrosis. A number of treatments can, however, relieve the symptoms and prevent numerous complications.

Doing exercises to clear thick mucus build-up from the airways is one of the most important treatments. If done regularly, these exercises help the lungs to function at full capacity and reduce the number of lung infections that people with cystic fibrosis are prone to.

Antibiotics may be given as prevention to lower the risk of lung infections.

Other measures recommended to the affected person are as follows:

  • avoid contact with tobacco and other products that may irritate the airways;
  • have the flu vaccine; this measure is also recommended for all family members;
  • have the respiratory syncytial virus (RSV) vaccine;
  • take pancreatic enzymes, vitamins or other medications prescribed by a physician.

Continued breastfeeding is recommended for the affected child, if possible.

Information and support resource

Last update: February 14, 2020


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