The purpose of genetic risk factor screening for Permanent Hearing Loss (PHL) is to identify babies with at least two gene mutations in any one of the genes tested because these children have a higher chance of having PHL at birth or developing PHL in early childhood. Risk factor screening specifically looks for PHL that runs in families (or is inherited) in an autosomal recessive way in each of the 3 genes tested. While risk factor screening looks to identify babies who have a higher chance to have or develop hearing loss, it is also able to find babies who have only one copy of a gene mutation. People with only one copy of an autosomal recessive mutation are at low risk to have PHL and are called “carriers”.
Carrier status is not reported as part of the risk factor screening report for PHL. Learning about a child’s carrier status is optional. A parent or guardian may or may not wish to obtain this information about their child.
Carrier results are available by request from NSO for babies born on or after July 29, 2019 who had risk factor screening. See below for some reasons why parents/guardians may or may not want to learn about their child’s carrier status. Parents/guardians who wish to learn more about obtaining these results can contact NSO.
If you are the parent of a child who has PHL and your child’s risk factor screening result was screen negative, you may wish to ask your child’s health care provider to request further interpretation of these results. This further interpretation (note: no extra testing or sample is needed from your child), may tell you and your health care provider that your child has one copy of a hearing loss gene mutation. If this is the case, additional genetic testing in your child could be helpful to understand the meaning of this finding and whether it helps to explain your child’s hearing loss.
If you have a family history of early, childhood onset PHL, regardless of your child’s risk factor screening results and whether or not your child has PHL, you may wish to seek a referral to your local Genetics Clinic for genetic counselling and more information.
Some of the reasons that parents may choose to learn about their child’s carrier status are listed below.
- Other children in the family (i.e. siblings): If a child carries an autosomal recessive mutation for PHL, it is almost certain that at least one of the parents is also a carrier. More rarely, both parents could be carriers. If both parents are carriers, then there is a 1 in 4 (25%) chance each child of these two parents could inherit two mutations and be at higher risk to have early-onset PHL. Typically, carriers themselves do not have PHL.
- Your child’s future children: Some parents choose to learn their child’s carrier result so that they can tell their child this information in the future when he or she is planning their own family.
- Sharing information with other family members: If a child carries an autosomal recessive mutation for PHL, it means that other family members (i.e. brothers, sisters, aunts, uncles, cousins etc) may also be carriers.
Mostly the reasons for wanting to know are related to having information to help predict if a child in the family will have early onset PHL. If a child is predicted to be at higher risk to have PHL, then a plan can be put in place to test and/or monitor the child’s hearing as early as possible. Remember though, that all infants born in Ontario are offered newborn hearing screening and the option of risk factor screening regardless of whether there is an increased risk for PHL in a baby or family.
Some of the reasons parents may not want to know about their child’s carrier status are listed below:
- Most carriers of a recessive mutation for PHL are not detected through risk factor screening: The risk factor screen for PHL only looks for a few (and not all) gene mutations in the GJB2, GJB6, and SLC26A4 genes. This means that only carriers of these selected mutations in the genes tested can be identified. A person who is not found to be a carrier of any of the mutations on the risk factor screen could still be a carrier of another gene mutation in any of these 3 genes. Also, there are many other genes not included on the risk factor screen that are related to causing early-onset PHL that any person could have a mutation in/be a carrier of.
- Learning this result is not urgent: Carriers have a low risk to have early onset PHL and do not need any special or different care than other children. Some parents wait until their child is old enough to make their own decision whether to learn their carrier results.
- Increased worry: Some parents say that learning their child was a carrier made them worry about their child’s hearing or treat their child differently, even though their child is not at high risk to have PHL.
- Non-paternity: If a child is found to carry a recessive mutation for PHL, the parents could be offered the option of carrier testing to determine if either of them are also carriers. This testing could indicate that the person thought to be the child’s father, is not actually the biological father.
If you would like to request your child's carrier status for PHL, please contact NSO.