Are you confident that you have the knowledge to support your preconception or pregnant patients with genetic carrier screening?

In November last year, the Federal Government announced a range of new Medicare rebates to allow more Australians to access the latest advances in genetic testing. These changes are summarised below:

1. New Medicare rebates are available for:

  • Reproductive carrier testing for couples to determine their combined risk of having a child born with cystic fibrosis, spinal muscular atrophy or fragile X syndrome
  • Genetic testing to diagnose mitochondrial disease
  • Genetic testing for childhood hearingGene panel testing for haematological malignancies
  • Small gene panel testing for non-small cell lung carcinomaTargeted carrier testing for severe monogenic conditions
  • Detection of measurable residual disease in patients with acute lymphoblastic leukaemia
  • Prognostic gene expression profile test to determine the risk of early and late metastasis in node negative and positive breast cancer under endocrine treatment
  • Testing for specific genetic variants that cause nine severe conditions commonly found in the Ashkenazi Jewish population

2. Amended Medicare rebate is available for:

  • Genetic testing for cardiac arrhythmia to align with genetic testing for cardiomyopathy (item 73418)

3. Expanded eligibility for:

  • Testing for breast, ovarian, fallopian tube or primary peritoneal cancer.

While the 34 new, expanded or increased rebates are welcome, together with today’s health consumers being more informed than ever before (and hence more likely to raise genetic issues), they emphasise the importance of GPs having a good understanding of the fundamentals of genetic testing, particularly in the setting of preconception care.

While no single article can cover the topic comprehensively, here we highlight three key steps GPs need to follow when caring for patients who should undergo genetic carrier screening.

Step 1: Take a comprehensive family history

GPs are well placed to take a comprehensive family history from both members of the couple to identify any known increase in the risk of having a baby with an inherited genetic disorder. The Royal Australian College of General Practitioners Genomics in General Practice resource has a comprehensive guide on how to take a genetic family history for your patients.

The questions you may like to ask your patients include, “do you have any relatives with any known genetic conditions?”, “do you have any relatives with an intellectual disability?”, “are you and your partner related to each other in any way?” as consanguinity increases the chance that both members of thecouples will be carriers of the same condition.

Step 2: Offer genetic carrier screening to your patients

It is important that patients understand their individual and joint risks of having a baby with an inherited genetic condition. While no test guarantees with absolute certainty the outcome of a particular pregnancy, advancing genetic technology is playing an increasing role in offering couples more information about their risk.

The Royal Australian College of Obstetricians and Gynaecologists (RANZCOG) advises that all women who are planning a pregnancy or who are in their first trimester of pregnancy be offered carrier screening, such as the expanded carrier screening which does not currently attract a Medicare rebate or the 3-Gene Carrier Panel (Cystic Fibrosis, Fragile X syndrome and Spinal Muscular Atrophy), which does attract a Medicare rebate. These tests should be offered regardless of whether they have family members with genetic conditions. Approximately 1–2% of non-consanguineous couples have a one in four chance of having a child with an autosomal recessive or X-linked recessive condition.

The conditions in the 3-Gene Carrier Panel are inherited in either autosomal recessive or X-linked recessive pattern respectively. For autosomal recessive conditions determining the carrier status of both partners is important, whereas in Fragile X syndrome it is the carrier status of the patient who is pregnant or planning to become pregnant which is important. See here for more information.

The new MBS item numbers are intended to be first used to test hte patient who is pregnant or planning pregnancy for Cystic Fibrosis (CF), Spinal Muscular Atrophy (SMA) and Fragile X Syndrome (FXS). Subsequently, the reproductive partner is assessed for their carrier status for CF and SMA only. This is because the FXS carrier status of the reproductive partner is not directly relevant in determining whether a child will be born with FXS.

Step 3: Consider a referral to a Clinical Genetics unit

Clinical geneticists have extensive knowledge about complex genetic testing and counselling of patients and family members. Genetic counselling may be offered by the pathology company who performed the genetic testing which identified an increased risk for a couple, sometimes at no cost to the patient. Separate to this service, a referral to a Clinical Genetics unit at a tertiary hospital can also be considered, even if carrier testing has returned a normal result. For example, if you are caring for a couple with a family history of inherited genetic conditions, neurological conditions or intellectual disability, or to interpret the results of complex genetic test results.

Genetic testing is a complex and growing area of Medicine which requires constant upskilling. Understanding the terminology used within genetic assessment, testing and counselling is crucial in order to clearly communicate this information to patients and support them to seek further advice. The Genetics for GPs Course developed by Flinders University and GPEx provides GPs with a more comprehensive understanding of clinical genetics as it relates to their day-to-day practice.

Genetics for GPs course