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Bulk-Billed Genetic Carrier Screening: GPs’ Vital Role in Antenatal Patient Care

The introduction of bulk-billed Genetic Carrier Screening for cystic fibrosis, spinal muscular atrophy, and fragile X syndrome to the MBS in November 2023 was a welcome addition for both patients and doctors alike. It helped raise awareness of this important screening and increased accessibility for Australians who would not have been able to afford it otherwise.

As carrier screening is ideally performed before conception to offer greater reproductive choice, this has highlighted the important role GPs play in preventative antenatal care. GPs are ideally positioned to discuss Genetic Carrier Screening early on, before a woman conceives, during the planning stage of her pregnancy journey. Ordering the screening for patients is easy, as it is hosted as a template in Best Practice, under the name “Genetic Carrier Screening Request Form.”

If screening is performed before pregnancy, this allows more time for counselling and discussion about other reproductive choices, such as pre-implantation genetic diagnosis through IVF, using donor eggs (or donor sperm for CF and SMA), donor embryos, or adoption.

While it is recommended that testing be completed prior to pregnancy so that this essential information is known early, is it still vital that women in the first stage of pregnancy are tested as well. This ensures they have the opportunity to make informed decisions for their family.

RECOMMENDED BY CLINICAL GUIDELINES

Genetic Carrier Screening should now be a routine part of pre- and early-pregnancy clinical management by GPs and specialists, as it is recommended in both RANZCOG and RACGP guidelines that this screening be offered to every woman and couple who are planning or in the first stage of pregnancy, regardless of their risk factors.

If a patient has had one or more unaffected pregnancies but was never offered genetic carrier screening in the past, it is still important to offer the screening before any subsequent pregnancies, as she may be a carrier and not know it.

MEDICARE-REBATABLE CONDITIONS

Bulk-billed Genetic Carrier Screening covers the three most common inherited conditions: cystic fibrosis (CF), spinal muscular atrophy (SMA), and fragile X syndrome (FXS). One in 20 people are carriers of at least one of these conditions, and 90% of carriers have no family history.

Cystic Fibrosis (CF)
CF is a severe autosomal recessive genetic condition that causes lung and gastrointestinal problems. Approximately 1 in 25 individuals are carriers of CF, and CF affects about 1 in 2,500 people. Clinical Labs’ CF screening covers more than 75 common mutations in the CFTR gene.

Spinal Muscular Atrophy (SMA)
SMA is an autosomal recessive inherited neuromuscular disease historically associated with high morbidity and mortality. Approximately 1 in 35 individuals are carriers of SMA, and SMA affects about 1 in 6,000 people. Clinical Labs’ SMA screening identifies deletions of the SMN1 gene (one copy), which account for approximately 96% of the mutations in this gene.

Fragile X Syndrome (FXS)
FXS, an X-linked condition, is the most common inherited form of intellectual disability. Approximately 1 in 330 individuals are carriers of FXS, and FXS affects approximately 1 in 3,600 men and 1 in 6,000 women. FXS carrier screening is recommended for females, as it is inherited in a different way to CF and SMA.

Female patients who have the gene change (number of CGG triplet repeats) in the FMR1 gene are found to be at risk of having a child affected by FXS, as the abnormal gene may expand over generations. The size of these CGG triplet repeats determines the chance of the FXS gene failing to function in a normal way and, therefore, the clinical presentation.

MEDICARE ELIGIBILITY CRITERIA

Bulk-billed genetic carrier screening is now available to determine a couple’s combined risk of having a child with a genetic condition. Testing is available for all individuals, even those with no symptoms or family history.

New items 73451 and 73452
The patient who is planning pregnancy or already pregnant should be tested first under MBS item 73451 prior to testing the reproductive partner patient under MBS item 73452 to ensure an informative and clinically relevant test result is obtained in the relevant gene.

73451
Testing of a patient who is pregnant or planning pregnancy to identify carrier status for pathogenic or likely pathogenic variants in the following genes, for the purpose of determining reproductive risk of cystic fibrosis, spinal muscular atrophy, or fragile X syndrome:

a) CFTR;
b) SMN1;
c) FMR1.

One test per lifetime.

73452
Testing of the reproductive partner of a patient who has been found to be a carrier of a pathogenic or likely pathogenic variant in the CFTR or SMN1 gene identified by testing under item 73451, for the purpose of determining the couple’s reproductive risk of cystic fibrosis or spinal muscular atrophy.

One test per condition per lifetime.

UNDERSTANDING THE TEST RESULTS

PATIENT is a CARRIER
If the PATIENT is found to be a CARRIER for CF or SMA, then testing of the reproductive partner is RECOMMENDED for that specific condition.

PATIENT is NOT A CARRIER
If the PATIENT is found to be a NON-CARRIER for CF or SMA, then testing of the reproductive partner is NOT REQUIRED.

PATIENT and REPRODUCTIVE PARTNER are BOTH CARRIERS
If the REPRODUCTIVE PARTNER is also found to be a CARRIER for CF or SMA, then genetic counselling is recommended. For positive cases (tested by Clinical Labs), Clinical Labs offers one genetic counselling session per couple at no cost.

PATIENT is in the PRE-MUTATION or FULL MUTATION RANGE for FXS
If the patient is found to be in the pre-mutation or full mutation range for FXS, then genetic counselling is recommended. For FXS testing with Clinical Labs, only pre-mutation and full mutation cases are offered genetic counselling.

Clinical Labs’ Genetic Carrier Screening Request Form for CF, SMA, and FXS is hosted as a template in Best Practice. It can be found under the name “Genetic Carrier Screening Request Form.”

For more information on Genetic Carrier Screening test options and other antenatal testing services offering by Clinical Labs, please visit antenatal.clinicallabs.com.au/doctor

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