Contributed by: Nanci Baren
What is Cystic Fibrosis?
Cystic fibrosis (CF) is an inherited disease caused by a genetic defect that interferes with the body's ability to carry salt and water to and from cells. This causes buildup of thick mucus that clogs up the lungs and digestive organs. Many people recognize cystic fibrosis as a lung disease but are unaware that the mucus buildup affects other organs as well.
Organs affected by CF include:
Lungs
Pancreas
Liver
Intestines
Sinuses
Reproductive organs
Cystic fibrosis is one of the most common genetic diseases and affects about 1 in every 2500 babies born in the United States. It is most common among Caucasians and Hispanics, and rarely occurs in people of African or Asian descent.
What Are the Symptoms of Cystic Fibrosis?
The symptoms of CF can vary depending on the stage of the disease and the organs that are affected.
Early symptoms:
Increased appetite
Poor growth
Oily, bulky, foul-smelling bowel movements
Salty tasting skin
Frequent coughs
Frequent respiratory infections
Difficulty breathing
Advanced symptoms appear in the form of complications, including:
Unexplained weight loss
Diabetes
Pancreatitis
Liver disease
Infertility
How is Cystic Fibrosis Diagnosed?
Cystic fibrosis is diagnosed by testing blood, sweat or fetal cells for the presence of substances or genes found in CF patients.
Pregnancy
If an expectant couple knows or suspects that they might be carriers of the CF trait, an amniocentesis or chorionic villus sampling can be done during pregnancy to determine if the baby will have the disease.
Newborn
Currently, 40 states include cystic fibrosis in their newborn screening tests. Blood is taken from the baby's heel before he or she goes home from the hospital. The blood is sent to a state laboratory and if the defect is detected the primary care physician and local health agencies will be notified.
Infancy and Childhood
If not detected at birth, cystic fibrosis is often diagnosed in the first year or two of life when a child begins to show the typical warning signs. The traditional test for cystic fibrosis is the sweat test. Because the body is not able to use all the salt it takes in, most people with cystic fibrosis will usually excrete larger than normal amounts of salt in their sweat.
In a sweat test, electrodes are placed on the patient's skin to stimulate the sweat glands. Sweat is collected and sent to a laboratory to measure the salt content. The sweat test is not painful, and has been used for many years to diagnose cystic fibrosis.
How is Cystic Fibrosis Treated?
There is no cure for cystic fibrosis. Treatment involves a combination of medication, diet, exercise, and therapies designed to control symptoms and prevent complications.
Medications are prescribed to:
Prevent and control respiratory infections
Keep airway open and help with breathing
Loosen and remove sticky mucous
Help the body absorb nutrients
Diet and nutrition plans are prescribed to:
Replace vitamins that cannot be stored
Ensure calorie intake meets high energy demands
Ensure adequate nutrient intake for proper growth and development
Replace salt that is lost through sweat
Exercise and therapies are prescribed to:
Strengthen the heart and lungs
Loosen and clear mucus
Improve endurance and overall physical condition
Increase the amount of oxygen delivered to tissues
What Causes Cystic Fibrosis?
CF is caused by a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The job of the CFTR gene is to make a protein that controls the movement of salt and water in and out of all the cells in our bodies.
Each of us has two copies of the CFTR gene because we got one from each of our parents. Sometimes the CFTR gene that we get from our parents is abnormal, but that doesn't always mean we will have CF.
If a person inherits:
2 normal CFTR genes: He or she will not have CF and will not be a carrier.
1 normal CFTR gene and 1 abnormal CFTR gene: He or she will not have CF but will carry the defective gene and could pass it on to his or her children.
2 abnormal CFTR genes: He or she will have CF disease.
Can Cystic Fibrosis Be Prevented?
Because cystic fibrosis is an inherited disease, it cannot be prevented. However, the presence of the defective CFTR gene can be detected by a simple blood test. Before conceiving a child, couples who know or suspect that one or both partners might carry the CF defect should seek genetic counseling to determine their risk of passing on CF disease.
What Is Life with Cystic Fibrosis Like?
It wasn't so long ago that children with cystic fibrosis rarely lived beyond adolescence. Now, much is known about the disease that was not known in the past. This knowledge has led to treatment regimens that allow people with cystic fibrosis to live active and productive lives well into adulthood. People living with cystic fibrosis need to take extra precautions against infections. They will also need to take digestive enzymes, inhaled antibiotics, and other medicines for the rest of their lives. Men are usually infertile, women may be less fertile but still able to conceive.
Sweat Test
The Gold Standard Diagnostic Test for Cystic Fibrosis
Electrodes placed on arm for sweat test
Photo © A.D.A.M.
The sweat test has been the test of choice for diagnosing cystic fibrosis (CF) since 1959. Newer methods, such as genetic testing, have been developed but in most situations, the sweat test is still the test that leads to CF diagnosis. Some reasons for having a sweat test are:
A baby has had a positive newborn screening for CF
A person of any age has symptoms of CF
What Happens During a Sweat Test?
The sweat test is usually done on the forearm, but may be done on the thigh of infants and children with small arms.
First Step - Stimulating Sweat: The technician will place two electrodes containing a sweat-inducing drug called pilocarpine on the skin. A small electric current is delivered through the electrodes to help the pilocarpine stimulate sweat. The current is not painful, but a slight tingling sensation may be felt.
Second Step – Collecting Sweat: After about 10 minutes, the technician stops the current and removes the electrodes. The skin is wiped dry and a piece of filter paper covered with plastic, sometimes called a "sweat patch" is placed on the site to collect the sweat. When a sufficient amount of sweat is collected, usually about 30 to 45 minutes, the sweat-drenched paper is removed and sent to the lab for testing.
What Does the Sweat Test Look For?
People with cystic fibrosis have high levels of salt, known as sodium chloride, in their sweat. The sweat test measures the amounts of sodium and chloride in the sweat, but the amount of chloride is the factor that determines the outcome of the test.
Chloride Ranges in Infants:
less than 30 = normal
30 – 59 = borderline
60 or greater = positive for CF
Chloride Ranges in Children and Adults:
less than 40 = normal
40 – 59 = borderline
60 or greater = positive for CF in children, but could still be normal for adults. If an adult has a result close to 60 mmol/liter, genetic testing may be done to confirm the diagnosis.
How Accurate is the Sweat Test?
The sweat test is 98% accurate, but some factors can cause the results to be incorrect or inconclusive.
False positives: Certain rare disorders can also produce high chloride levels in sweat, but those disorders have different symptoms than cystic fibrosis. If a sweat test produces positive results in a person who has symptoms that are not typical for CF, further testing should be done to confirm the diagnosis.
False negatives: Sometimes, a person with cystic fibrosis will have a normal chloride level in his or her sweat. If this happens, it is usually either because not enough sweat was provided in the sample, or the sweat was diluted.
False negatives are most often seen in:
Infants less than 2 weeks old or weighing less than 7 pounds who may not be able to produce enough sweat.
People with tissue swelling caused by fluid retention, known as edema, whose sweat may become diluted with tissue fluids.
Treating Cystic Fibrosis
Keeping Things Running Smoothly
Cystic fibrosis is a disease for which there is no known cure. The goals of treatment are to alleviate symptoms, slow the progress of the disease, prevent complications, and thereby increase the quality of life for the CF patient.
Team Approach
Studies have shown that outcomes are better when cystic fibrosis patients receive treatment by a team of specially trained professionals at one of the 115 accredited CF centers throughout the United States.
The CF team members often include:
Doctors
Nurses
Nutritionists
Social Workers
Physical Therapists
Respiratory Therapists
Psychologists
Pharmacists
Medications
People with cystic fibrosis will have to take medications for the rest of their lives. Some of the common medications are:
Antibiotics: Taken to prevent or cure an infection. Sometimes the antibiotics are taken by mouth, and sometimes they are a liquid that is vaporized and inhaled using a machine called a nebulizer.
Anti-inflammatory: An anti-inflammatory is a drug that reduces irritation and swelling. Anti-inflammatory drugs may be prescribed to CF patients to reduce the swelling in the lungs and breathing passages.
Steroids are one type of anti-inflammatory drug, but they are not used very often in CF treatment anymore because they can cause diabetes or problems with the kidneys and bones. Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are more commonly prescribed in CF treatment.
Enzymes: One of the problems caused by CF is that the thick secretions in the pancreas prevent it from releasing the enzymes the body needs to digest food. If the food is not digested, the body can't absorb any nutrients. People with CF need to take pills that contain the necessary enzymes before each meal.
Mucolytics: Mucolytics are medicines that help to thin mucus and make it easier to cough out. They are often prescribed to cystic fibrosis patients to help them clear their airways of the thick, sticky mucus that CF causes. Sometimes mucolytics are taken by mouth and sometimes they are inhaled using a nebulizer.
Airway Clearance
An essential part of cystic fibrosis treatment is the use of a variety of techniques to help loosen and remove mucus. Cystic fibrosis patients must have this therapy several times a day. The therapy will involve one or more of these techniques:
Chest Physical Therapy (CPT): This therapy uses a technique called percussion that involves rhythmic tapping of the hands on strategic areas of the chest. With newly diagnosed CF patients, a respiratory therapist or nurse will usually do CPT but parents will be taught how to do it so they can take over therapy at home. A typical CPT session lasts about 30 minutes, and will need to be done up to four times per day.
Vibration: Another technique that is sometimes done along with percussion during CPT is vibration. This is also done with the hands, but as the name implies, a vibrating motion is used rather than a tapping motion.
Postural Drainage: During CPT, the patient is placed in positions that will allow gravity to help the loosened secretions flow out of the lungs. This is known as postural drainage.
Inflatable Therapy Vest: Sometimes, instead of manual CPT, a device called and airway clearance vest will be used. The vest inflates and deflates rapidly to loosen mucus through a gentle squeezing motion. The benefits of the using the vest are that the patient can do therapy without help, and the sessions last only about 20 minutes.
Flutter Device: Also known as a flutter valve, this small hand-held device looks similar to an inhaler. The patient puts the mouthpiece in his or her mouth and exhales forcefully. The device uses the exhaled air to create vibrations of the chest.
Diet
People with cystic fibrosis don't absorb nutrients properly from the food that they eat, and the work of breathing causes them to burn extra calories. This double whammy causes malnutrition and poor growth. To combat nutrition problems, CF patients require up to 50% more calories than other people their age. Nutritionists create individualized diet plans tailored to the needs of each patient, but usually people with cystic fibrosis can expect to:
Eat 3 meals and 2-3 snacks per day
Eat foods high in protein and fat
Drink nutrition shakes once or twice a day
Take vitamin supplements, especially vitamins A, D, E, and K, which are not stored well in people with CF.
Exercise
Physical activity has both short-term and long-term benefits for people with cystic fibrosis. The immediate benefit is that exercise forces more air through the lungs and helps loosen mucus. The long-term benefit of exercise is that it helps improve cardiovascular health and endurance, which gives the body extra stamina to fight the effects of CF.
Lung Transplantation
When cystic fibrosis progresses and causes severe lung damage, lung transplation may be a treatment option for people who meet the criteria. While lung transplantation is not an option for everyody, it has proven to be quite successful for some CF patients. More than 1600 people with cystic fibrosis have received lung transplants, and about half of them have survived for at least five years after after receiving their new lung.
Sources:
Bilton, D. (2008). Cystic fibrosis. Medicine. 36, 273 – 278.
Pitts, J., Flack, J., & Goodfellow, J. (2008). Improving nutrition in the cystic fibrosis patient. Journal of Pediatric Health Care. 22, 137-140.
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