CF gene mutation testing can be done to screen the general population or to screen a targeted (higher risk) subset of the population for carrier status. It can be used to confirm the diagnosis of CF in a symptomatic patient with an elevated IRT or sweat chloride test.

It can be used, along with genetic counseling, to establish carrier status and the risk of an infant with CF as part of a prenatal workup. This may be done by sequential or couple testing. In a sequential strategy, the mother is 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. If she is a carrier, then the father is also tested for carrier status. With couple testing, both parents are tested at the same time. In either case, follow-up counseling provides couples with information on what it means to be a carrier, and they are informed about the residual risk of being a carrier even if their panels were negative (e.g. there is still a slight risk that rare mutations might be present).

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.

A doctor may order CF gene mutation testing to rule out CF if the patient has symptoms such as salty sweat, persistent respiratory infections, wheezing, persistent diarrhea, foul-smelling bulky greasy stools, malnutrition, vitamin deficiency or male infertility.

CF gene mutation testing may also be ordered to confirm a CF diagnosis following a positive sweat chloride or IRT test. It may also be ordered as a targeted general population screen, as part of a genetic counseling workup prior to conceiving, or as an “at risk” screen, if, for example, the patient has a close relative who has been diagnosed with CF.

If the CF gene mutation test is positive - it comes back with two identified gene mutations - then the patient has CF. The test, however, cannot tell how severe or mild the symptoms may be. Patients with the exact same mutations may have very different outcomes.

If the test comes back negative for mutations and the patient is asymptomatic, chances are that they do not have CF and are not a carrier. There is still a slight risk that the person could be a carrier of a rare mutation not identified with the standard panel.

If the CF gene mutation panel test 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 patient 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.

If the CF gene mutation test 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 you are identified as a carrier, your siblings may also want to verify their carrier status.

Early detection of CF allows patients 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 patient’s quality of life and minimize CF complications.