Clinical Genetics Unit, Birmingham Women’s Hospital

Genetic counselling
is the process by which patients or relatives at risk of a disorder that may be hereditary are given information about the consequences of the disorder, the probability of developing or transmitting it and of the ways in which it may may be prevented, avoided or ameliorated.

Investigation and diagnosis of a possible genetic disease
Genetic counselling requested after the diagnosis of a genetic disease
Strong family history of cancer
Interpretation of abnormal prenatal diagnostic results
Family history of chromosomal translocation
Testing family members for carrier status for single gene (mendelian) disorders
Diagnosis of mental handicap, especially if there is a family history of several boys affected
Diagnosis of a syndrome in a child with multiple malformations or dysmorphic features
Are presymptomatic diagnosis, prenatal diagnosis, or gene tracking by DNA tests available?
Organisation of specialised prenatal diagnosis
Cousin marriage

Timing of genetic information

The diagnosis of a serious genetic disorder or malformation syndrome during pregnancy may leave the family with relatively little time to understand the severity and consequences of the disorder, ascertain options open to them (including any treatments available) and discuss genetic implications. Families particularly want to know whether the condition is lethal or severely disabling, if there is a high risk in a future pregnacy and whether specific prenatal diagnosis would be available. Couples who have sought this information before embarking upon a pregnancy have time to decide the options which they consider correct for them. During pregnancy difficult management decisions may have be made relatively speedily. Some carrier detection tests are not accurate during pregnancy

Genetic information may therefore play an important role in the consideration of options which may include

• having no (more) children
• accepting the risk
• undertaking prenatal diagnosis (if available)
• seeking adoption
• gamete donation
• preimplantation diagnosis

A couple’s choice will depend on many factors, social, economic, moral and practical, and may be different at different times in their lives.

The genetic consultation

Genetic counselling involves three main steps

a) making an accurate diagnosis
b) describing the consequences of the disorder, the probability of developing and transmitting it
c) discussing the ways in which this may be prevented or ameliorated.

The information is given in a non-directive manner as it is important that the family reach their own decisions. The risk of transmitting a disorder, the severity of a disorder, the availability of prenatal diagnosis, and moral, social and religious convictions influence people as they consider the options which are available to them. Support should be offered to the family whilst they come to terms with often very difficult decisions.

The consequences of performing carrier tests on children should be considered carefully. Stigmatisation must be avoided.

It is a widely held view that children should not be tested for carrier status before the age at which they can make the decision for themselves and can understand the implications of the test and the subsequent genetic consequences. It is likely that the request will come from a family with an affected member and so the consequences of the disease may be well known. Misconceptions about the genetics of the condition must be explored; some carriers of autosomal recessive traits do not appreciate that they are at risk only if their partner is also a carrier.

The person tested may not need to act on the information about carrier status for many years, and so the result should also be sent to the general practitioner for the primary care health records. Regional Genetics Units may operate a review and recall system (often called a genetic register) specifically to offer carrier testing. Most units provide this service for sisters of boys affected with Duchenne muscular dystrophy, for example, as well as other diseases.

Genetic testing for presymptomatic disease may be indicated if surveillance for serious complications or preventative therapy can be instituted, but should be discussed fully with the parents and a senior colleague before proceeding. There is a widespread view that predictive testing for adult onset diseases such as Huntington's disease should not be contemplated until the child is able to take the informed decision.

Indeed, an adult requesting a presymptomatic test agrees to follow an internationally agreed protocol before DNA testing is performed.

They can allow
a) confirmation of diagnosis (especially helpful in diseases where clinical features can be equivocal)
b) carrier testing (especially where biochemical testing is not available or the results may be equivocal)
c) presymptomatic diagnosis so that surveillance can be instituted (for instance in familial adenomatous polyposis coli)
d) precise estimation of risk
e) prenatal diagnosis

Each family has to be individually assessed because some techniques rely on the family structure and the necessary DNA samples being available.