CARRIER SCREENING TEST FOR CYSTIC FIBROSIS

Cystic fibrosis is a genetic disorder in people with defective cystic fibrosis transmembrane conductance regulator gene, which in normal individuals helps in controlling the chloride channel in cells of respiratory, digestive and reproductive system. The disorder has significant prevalence in many parts of the world and in united status about 30000 children and adults are affected with this disorder. The disorder induces severe breathing and digestion complication in patients, due to blockage of the pathway or passage due to extreme secretion of mucus. This thick and sticky mucus in turn promotes growth of bacteria and causes life-threatening infection in the patients. The excess of secretions in pancreas also lead to complication with absorption of food and causes complications. Average lifespan of patients diagnosed with cystic fibrosis is till 30-37 years, but in many cases with modern medications and treatment interventions, life expectancy till 40 is also being achieved.

Normal individuals have two working alleles of the cystic fibrosis transmembrane conductance regulator gene, and even one allele of the gene is enough to prevent occurrence of cystic fibrosis. Hence in this disorder, symptomatic patient has two allele of the defective cystic fibrosis transmembrane conductance regulator gene in their body, which is generally inherited by both of their parents. The person with only a single defective gene acts as carrier of the disorder and may not express the symptoms of cystic fibrosis.

Cystic fibrosis carrier test can be performed as a pre- natal diagnosis to determine the presence of abnormal gene in the prospective parents. It can be tested using blood or saliva of the prospective parents and can confirm the increased risk for having a child with cystic fibrosis. If one parent has carrier gene for cystic fibrosis, then none of their children will have this disorder. When both parents have cystic fibrosis carrier gene, then there is 1 in 4 chances to have to baby with symptomatic cystic fibrosis and about 1 in 2 chance that the child will also be a carrier and will show the symptoms of cystic fibrosis.

The prevalence of cystic fibrosis is seen more in Caucasians, and the American college of obstetrician and gynecologists recommends performing carrier test to all pregnant Caucasian women. Individuals with a family history of cystic fibrosis should also test for the CF carrier gene, before having children

the carrier screening test is recommended since 1989, when the defective cystic fibrosis transmembrane conductance regulator gene was discovered and found to be the causative agent for the cystic fibrosis disorder. Studies showed that cost effectiveness of CF carrier test can be observed, when the test is performed in sequential manner with an intention to terminate the pregnancy in case it is affected. The information gathered from the carrier screening test should also be used in more than one pregnancy, which actually makes it more cost effective in case of population wide screening for CF carrier gene.
The carrier screening test helps the parents to provide the best healthcare and suitable environment to child who might have the disease but do not express it being a carrier of the disorder.