Cystic fibrosis is an inherited disease that affects mainly the lungs, pancreas, and sweat glands. It leads to the production of thick, sticky mucus and can cause recurrent respiratory infections and impaired function of the pancreas.
The CF mutation panel can be used as part of a prenatal workup to establish carrier status in prospective parents and therefore determine the risk of CF in their infant. The American College of Obstetricians and Gynecologists recommends that carrier screening be made available to all women of reproductive age to identify couples at risk of having a child with CF. This is typically done by sequential testing. In a sequential strategy, the mother is usually tested first. If she is not a carrier, then any child she had would, at most, be a carrier from the father's side. Using this logic, the father is not tested. The American College of Medical Genetics recommends that a positive result for the mother should include the recommendation of testing her partner and at-risk family members and that all positive results for diagnostic tests or for positive/positive couple screening should indicate the need for genetic counseling. In addition, all CFTR carriers and any individuals who have a family history of CF should also be referred for genetic counseling.
CF gene mutation testing can also be used for prenatal diagnosis if both parents are known to be carriers and if their gene mutations have been previously identified. DNA from amniocentesis and chorionic villus sampling procedures, although somewhat invasive, can be used to test the fetus for the known parental mutations.
For prospective parents prior to conception or for a fetus to diagnose CF when mutations have been identified in both parents
To determine carrier status whenever it is desired or recommended and/or when someone has a close relative who has been diagnosed with CF
When a newborn infant has meconium ileus or when a person has symptoms of CF such as salty sweat, persistent respiratory infections, wheezing, persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, vitamin deficiency, or male infertility
Diagnostic test results If a CF gene mutation panel is positive - it comes back with two identified gene mutations - then the person has CF. The test, however, cannot predict how severe or mild the symptoms may be. People with the exact same mutations may have very different outcomes.
If the CF gene mutation panel reveals a single mutation or is negative and the patient is symptomatic, further mutation testing, a sweat chloride test, and/or other laboratory testing to check organ function are warranted. The person may have a more rare form of CF that has not been identified or may have a lung or pancreatic disease or condition other than cystic fibrosis.
Carrier test results If the CF gene mutation panel comes back with a single identified mutation and the patient is asymptomatic, then chances are that the person is a CF carrier. This may be information some individuals want to know before having children. If someone is identified as a carrier, then the siblings of this person may also want to verify their carrier status.
If the panel comes back negative for mutations and the person is asymptomatic, chances are that the person does not have CF and is not a carrier. There is still a slight risk that someone who tests negative could be a carrier of a rare mutation not identified with the standard panel.
Early detection of CF allows those affected to be referred to CF centers for specialized care, individualized treatment plans, and careful monitoring. Beginning treatments such as taking oral enzyme supplements and fat-soluble vitamins, learning how to clear mucus out of airways, and learning to recognize respiratory infections can improve a person's quality of life and minimize CF complications.
Doctors may have varying approaches to screening and diagnosing CF, and gene mutation testing may involve a series of steps. Sometimes, a doctor will choose to order a standard panel that includes 23 of the most common mutations. If results are negative and the clinical suspicion is still high that a person has CF, the doctor may then request that an expanded panel be performed, or a negative result may automatically generate (reflex) a request for an expanded panel. Based on the ancestry of the individual tested, some doctors may immediately start with the expanded panel. In either scenario, a negative screening panel result may lead to a request for gene sequencing, a method that can identify rare mutations not detected by the standard or expanded panel.
This article was last reviewed on January 17, 2013. | This article was last modified on January 17, 2013.
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