Carrier Testing for Genetic Disorders

What is a carrier test for?

A carrier test aims to establish if an individual “carries” an abnormality which might prove to be detrimental at reproduction. Being a “carrier” is generally harmless in terms of the person’s wellbeing but may prove damaging to offspring.

At its broadest definition, carrier testing includes patients who may carry structural rearrangement of the chromosomes and the tests offered to such patients are fundamentally different and focus on the integrity of the chromosomes, known as a karyotype. 

More commonly patients seek a carrier test for a single gene mutation.

Who should have a carrier test?

1- A person for whom a Genetic Diagnosis is established in a Family Member 

Most people seek carrier testing for a genetic condition because of a genetic diagnosis in a family member and this individual wishes to identify whether they themselves are “at risk” of having a child with the same disorder. Hence they seek to establish if they “carry” the mutation.

In Ireland, because we have a high prevalence of Cystic Fibrosis, carrier testing for this condition is often sought by people who have a relative with Cystic Fibrosis. The carrier rate in this country of mutation for Cystic Fibrosis is 1 in 19.

2 - A Female Relative of a Male for whom an Abnormal DNA Test is Established on the X Chromosome

Carrier testing can also be offered for a wide range of other genetic disorders, particularly if the genetic condition in a relative has been characterised and an abnormal DNA test already been established. 

Duchenne Muscular Dystrophy is a good example, the condition affecting boys and transmitted by females who are unaffected carriers of the mutation on their X chromosome. Once the condition has been established in a case in the family, testing for female relatives to establish whether they are carriers should be offered routinely. However, it does require that the correct analyses be undertaken to get the prediction correct as to carrier status.

3 - Any Person who wishes to Establish if there is a Possible Reproductive Risk

Increasingly, we are seeing couples attending for testing who do not have a family history of an established genetic condition. They simply seek to inform themselves as to whether there is a reproductive risk to them.

Couples Genetic Testing

NOTE: We are able to offer “couples testing” for over 300 of the more commonly identified genetic disorders to establish whether they share any carrier mutation in common which would have implications for pregnancy.