At a Glance
Why Get Tested?
When to Get Tested?
When a newborn infant has meconium ileus (no stools in the first 24 to 48 hours of life) or when a person has symptoms of CF; if a person has a positive sweat chloride or IRT test or a close relative who has been diagnosed with CF; when a patient is undergoing genetic counselling and wants to find out if they are a CF carrier with or without a family history; or for prenatal diagnosis when both partners have been identified as CF carriers
A blood sample drawn from an infant's heel; a spot of blood that is put onto filter paper; a blood sample drawn from a vein in the arm; or saliva collected via a mouthwash sample
The Test Sample
What is being tested?
The CF gene mutation test identifies mutations in the CFTR gene. Each cell in the human body (except sperm and eggs) has 46 chromosomes (23 inherited from the mother and 23 from the father). Genes on these chromosomes form the body's blueprint for producing proteins that control body functions. Cystic fibrosis is caused by a mutation in a pair of genes located on chromosomes 7. Both copies (alleles) of this gene must be abnormal to cause CF. If only one copy of the gene pair is mutated, the patient will be a carrier. Carriers are not ill, they do not have any symptoms, but they can pass their abnormal CF gene copy on to their children.
To date, almost 2,000 different mutations of the chromosome 7 gene have been identified, but only a few of the mutations are common. The majority of CF in Australia is caused by a mutation called delta F508.
When CF gene mutation testing is done, the laboratory specifically examines the CFTR gene on each chromosome 7 for a number of mutations. If the initial panel of mutations demonstrates a mutation, additional testing for other mutations may be indicated if the individual is suspected of having the disease.
How is the sample collected for testing?
A blood sample is drawn from an infant's heel, a spot of blood is put onto filter paper, a blood sample is obtained by inserting a needle into a vein in the arm or saliva is collected via a mouthwash sample.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.