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Genetic Counselling

Dr Genome:

Hello everyone. I'm Dr. Genome, a Clinical Geneticist. Development of genomic technology has advanced in recent years. Application of genomic medicine is becoming more important. In view of this, HA strives to promote genomic medicine, especially genetic counselling, so that patients in need could receive a more comprehensive medical care. Let me further introduce what genetic counselling is and what we need to pay attention to during the process.

Genetic counselling is a communication process to convey genetic information to patients and their families. Genetic counselling at HA is currently offered by doctors, nurses or genetic counsellors. The service consists of three parts, 'pre-test genetic counselling', 'genetic testing' and 'post-test genetic counselling'.

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Pre-test genetic counselling

Dr Genome:

As the name suggests, pre-test genetic counselling is the counselling service provided by healthcare professionals before testing. They'll analyse the current symptoms of patients, enquire their medical and family history, including medical records, developmental and pregnancy histories etc., and illustrate the pedigree diagram based on collated information for further analysis in diagnosing and explanation to patients. If necessary, patients will be offered the most appropriate genetic test based on their conditions and risks of inherited diseases.

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Genetic testing

Dr Genome:

While there are benefits to genetic testing, it is not without risks and limitations. The possible test results may induce concerns in patients as well as their families. Therefore, before carrying out any genetic tests, healthcare professionals would offer genetic counselling to patients for detailed discussion of the testing. Upon patients' understanding of the testing purpose and possible results, their agreement to proceed with genetic tests, as well as with their signed consent form, this process is known as 'informed consent'.

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Informed consent

Dr Genome:

With patient's informed consent, genetic testing can be processed to identify the changes in DNA, called 'genetic mutation'. Genetic testing is applicable to a variety of clinical situations, e.g. prenatal diagnosis, inherited diseases and prescription, which are closely related to treatment and patient care. The purposes of genetic testing are diagnostic: to help manage the diseases; predictive: to understand the risk of developing inherited diseases; instructive: pharmacogenomics as an example to help doctors providing the most appropriate drugs and treatment and polygenic risk scores to access a patient's genetic susceptibility to certain common diseases for further risk evaluation.

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Genetic testing methods: molecular testing and cytogenetics testing

Dr Genome:

Genetic testing methods can be categorised into 'molecular testing' and 'cytogenetics testing'. Common cytogenetics testing methods include 'karyotype' and 'FISH'. While molecular testing methods include 'sanger sequencing', 'chromosomal microarray', 'whole exome sequencing' and 'whole genome sequencing'. Some methods only examine one gene each time like 'sanger sequencing'. While other methods may inspect multiple genes or the entire genome such as 'whole exome sequencing' and 'whole genome sequencing'. Thus, it's essential to rely on doctors' clinical judgement and patient's symptoms of different diseases to select the most appropriate genetic test for patients.

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How to interpret the genetic test reports?

Dr Genome:

There're three possible results for genetic test reports namely 'disease-causing mutation found', 'no disease-causing mutation found' and 'variant(s) of uncertain clinical significance'. There're also five variant classifications including pathogenic, likely pathogenic, uncertain significance, likely benign and benign. Moreover, there would be 'incidental' findings that mean the unintentional discovery of any inherited diseases that are unrelated to the referral. The interpretation of test reports is based on the current technology and knowledge. Future technological advances may facilitate future interpretations. As a result, negative results may not necessarily imply exclusion of diagnosis. As the genetic test report can be difficult to decipher and understand, healthcare professionals equipped with related knowledge are needed to interpret reports and provide post-test counselling.

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Post-test genetic counselling

Dr Genome:

Post-test genetic counselling involves not only the explanation of test results, but also the hereditary information and treatment plans, as well as the provision of relevant support in relation to their psychological health, community resources and patient groups prior to referring patients out for further management. If necessary, genetic counselling or testing may be arranged for family members too.

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Genetic counselling

Dr Genome:

In short, genetic counselling is to help patients and their families with suspected or confirmed genetic conditions by providing them with testing, diagnosis and counselling, such that they can understand the hereditary nature, modes of inheritance, recurrence chances, prevention and management. If needed, clinical geneticists would refer patients to other specialties for follow-up. Genetic testing is voluntary. It'll be performed under patient consent along with appropriate pre-and post-test counselling.

If you wish to know more, please visit the following websites. Online Mendelian Inheritance in Man (OMIM), ClinGen Clinical Genome Resource, GeneReviews, Rare Disease Hong Kong and ClinVar

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Special thanks to Department of Clinical Genetics of Hong Kong Children's Hospital