Учебники / Genetic Hearing Loss Willems 2004

test is available. Genetic testing for deafness can be described as specific but not sensitive (33) as a negative test result may rule out mutations in a specific gene but since the cause could be a mutation in a di erent gene it does not rule out genetic factors completely. Prior to genetic testing parents therefore need to be made fully aware of the possible consequences and that, at present, in many cases the genetic cause will not be found.

To provide e ective genetic testing and counseling for deafness the needs and views of individuals need to be considered. Although a number of surveys have shown that many people would welcome genetic testing for deafness they have also shown that people often have misconceptions, with many, mostly those who are deaf themselves, opposing genetic testing (2,3,34,35).

Brunger et al. (3) found that 96% of hearing parents, with one or more deaf children, had a positive attitude toward genetic testing for deafness. The most common reason given for having a genetic test was to identify the cause of deafness. Other reasons were to help the a ected child’s medical management in the future and to determine a recurrence risk. Most people surveyed said they would be interested in having such testing themselves. Some parents said their decision to have other children might be a ected by genetic test results but none said they would choose to terminate pregnancy.

However, a significant proportion of parents wanting testing for their children felt there was no need for testing themselves or their other children as they were not deaf (3). Some parents even disapproved of testing, one being ‘‘opposed to eugenics.’’ Such apprehension and fears are consistent with other studies of public attitude toward testing for other diseases (36,37) and illustrate the variance in attitude toward genetic testing.

Such views are much more common among culturally Deaf people who have predominantly negative attitudes toward genetic testing, 55% of Deaf individuals feeling it would do more harm than good, 46% feeling it devalues deaf people, and 21% being ‘‘horrified’’ at the prospects of genetic testing (2). Such fears of the Deaf are deep rooted as, all too often throughout history, eugenics programs have included deafness as a condition to be removed from society (9,38). Whereas many hearing parents may view their deaf child as being disabled, people in the Deaf community do not view themselves as being disabled and often would prefer to have deaf children. They want to protect their Deaf culture and many see genetics as another way for the medical community to eradicate deafness (3).

Some deaf persons refuse genetic counseling for fear of being told not to have children (39). That results of genetic testing may deter some hearing parents from having further children is also a major concern to the Deaf community who feel this could lead to a reduction in the number of deaf children (2). Many deaf couples’ preference for deaf children and opposition to genetic testing is perhaps warranted as such testing is likely to confirm that

most with recessive deafness will have hearing children, unless they have mutations in the same gene. Thus while the majority of people welcome genetic testing for deafness, the views of the Deaf community need to be respected and taken into account.

With genetic testing also comes the possibility of PND. Most hearing parents feel that prenatal testing for deafness should be o ered (3), primarily to allow parents to prepare, e.g., learn sign language themselves and look for schooling needs. Only 21% of deaf persons approved of PND, with 8% of these preferring deaf children and 2% saying they would consider aborting a hearing fetus (35). Conversely, 6% of deaf and 16% of hearing persons with a deaf child or parent would consider a termination of pregnancy if the fetus were deaf. However, the majority of deaf individuals do not mind if their child is deaf or not (2,35). The decision to perform prenatal diagnosis for a nonlethal condition such as deafness relies largely upon the discretion of the clinician involved. In an international study looking at attitudes toward PND it was found that 35% of British and 9% of American genetic professionals would perform PND for a deaf couple wanting to have deaf children (40). That there is no obvious consensus of opinion on this matter highlights the need for discussion on such issues.

With the results of genetic testing known, whether positive or negative, comes the need to convey their meaning to the family. Somewhat worryingly, it has been found that parents who have received genetic counseling still have no better understanding of the genetics of deafness than those who have not had counseling (3,34). Parents frequently had little idea of the relative risk they had been given and almost none knew the chance for their deaf child of having deaf children. One third of those who received negative Cx26 testing, i.e., normal, felt their child ‘‘does not have the deafness gene,’’ while many of those where Cx26 was the cause became more fearful after the result and so may be less likely to have further children (3). Such misunderstandings are not surprising given the complexities of the genetics of deafness and with the parents already concerned about their child they are likely to be overwhelmed with the information given to them. Establishing a program of both preand posttest counseling will be important to enable parents and patients to fully understand the meaning and implications of any test result and thus make informed decisions about what is best for them and/or their child.

The role of the genetic counselor and clinical geneticists involved with a family is of course central to this process. Robin et al. (41) also found that although most pediatric otolaryngologists have a good understanding of genetics, many gave incorrect recurrence risks in some examples. Given the heterogeneity of deafness and the rapid advances being made, it is not surprising that otolaryngologists and genetic counselors will need to keep abreast of the genetic studies of deafness.

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