Genetic counselling and testing

Genetic testing can be used for various purposes, from preconception planning (refer to Chapter 1. Preventive activities prior to pregnancy), during pregnancy, for neonates (newborn screening), during childhood and right through to adult-onset familial diseases (eg cancer, cardiac and neurodegenerative diseases).

In order to identify patients who may be at risk of a genetic disorder, a comprehensive family history must be taken from all patients, and this should be regularly updated. A family history should include first-degree and second-degree relatives on both sides of the family and ethnic background. Age of onset of disease and age of death should be recorded where available.

Increased frequency and early onset of cancers in families, premature ischaemic heart disease or sudden cardiac death, intellectual disability, multiple pregnancy losses, stillbirth or early death, and children with congenital abnormalities may suggest the presence of genetically determined disease. Patients of particular ethnic backgrounds may be at increased risk and may benefit from genetic testing for specific conditions. Possible consanguinity (eg cousins married to each other) should be explored, for example, by asking, ‘Is there any chance that a relative of yours might be related to someone in your partner’s family?’ General Practitioners (GPs) should consider referral to, or consultation with, a genetic service (general or cancer genetics) for testing because test results, which rely on sensitivity, specificity and positive predictive value, are not straightforward. Testing often involves complex ethical, social and legal issues. The time on waiting lists for genetic services is usually longer than one month, so direct consultation and liaison by telephone are necessary when the genetic advice could affect a current pregnancy. On the basis of current evidence, whole genome sequencing is not recommended in low-risk general practice populations (refer to Chapter 15. Screening tests of unproven benefit).

Clinical genetic services provide testing, diagnosis, management and counselling for a wide range of genetic conditions. Reasons for referral include:

• diagnosis of a genetic condition
• family history of a genetic condition
• recurrence risk counselling (eg risk of recurrence in a future pregnancy)
• pregnancy counselling (eg preconception, consanguinity)
• prenatal screening and testing
• presymptomatic and predictive testing for adult-onset disorders (eg cancer)
• discussions surrounding genetic testing
• arranging of genetic testing.

Services such as paternity testing or genetic testing/management of very common genetic conditions (eg haemochromatosis) are not provided by clinical genetic services.

Use of a simple family history screening questionnaire (FHSQ) can help identify individuals who may require a more detailed assessment of their family history of cancer, heart disease or diabetes (refer to Appendix 2A. Family history screening questionnaire for a published and validated FHSQ).¹ This tool can be used as part of the patient assessment at their first visit to a practice. If a patient is uncertain about their family history, they can be asked to discuss the FHSQ with their relatives prior to completing the questionnaire. For patients with low literacy, the FHSQ may need to be completed with the support of a healthcare professional. A positive response to any question requires follow-up with a more detailed assessment of the family history. As family history can change, it is recommended that the FHSQ be repeated at least every years.

Table 2.1

Genetic testing: Identifying risks

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