Expanded Carrier Screening

A carrier screen analyzes a person’s genes to determine if that person is a carrier of a recessive or X-linked condition.  Expanded Carrier Screening looks at up to 289 different hereditary conditions that, together, occur in 1 in 550 births.

Recessive disorders are caused by changes (called mutations) in a person’s genes. Every person has two copies of most genes, one inherited from each parent. A recessive disease occurs when both copies of the same gene have a mutation.

A carrier is someone who has only one gene with a mutation and one gene that is unaffected. Carriers are typically symptom-free and do not know they carry a mutation. In some instances, the condition is inherited differently — only the female needs to be a carrier to have a baby at risk. Fragile X syndrome is an example of this.

Most of us are carriers of a handful of genetic diseases that do not impact our everyday lives. However, these conditions can be passed, unknowingly, to a child. If both members of a couple are carriers of the same recessive condition, they have a 1 in 4 chance with each pregnancy to have a child affected with a genetic disease.

Of the conditions that we test for: 

• Many improve with early intervention (e.g., Wilson disease and phenylketonuria)
• Some carry a risk for intellectual disability (e.g., Fragile X syndrome and Niemann-Pick disease)
• Several have limited or no treatment options (e.g., spinal muscular atrophy and Canavan disease)
• 70% of individuals screen positive for one or more conditions on the Expanded Carrier Screen
• 1 in 40 couples test positive for the same condition on the Expanded Carrier Screen

Access to such valuable information before or early in pregnancy allows time to make better family planning choices.

Expanded Carrier Screening sequences the entire gene to identify carrier couples of all ethnicities for up to 289 inherited disorders, such as Canavan disease, Cystic Fibrosis, Niemann-Pick disease, Tay Sachs, and Gaucher disease.

Expanded Carrier Screening is useful in meeting the recommendations provided by at least two Canadian physician societies — the Society of Obstetricians and Gynaecologists of Canada (SOGC) and the Canadian College of Medical Geneticists (CCMG). In their article, An Update for All Canadian Providers of Maternity and Reproductive Healthcare in the Era of Direct-to-Consumer Testing (August 2016), they provide several principles for carrier screening, which are summarized as follows:

1. Discuss the value and risk of reproductive carrier screening with all women/families considering a pregnancy (pre-conception) and with all pregnant women at their first prenatal visit.
2. Ask women, preferably preconception, about a family history or personal manifestations of intellectual disability, muscular dystrophy, or bleeding disorders. Pay particular attention to X-linked conditions, such as Fragile X syndrome and Duchenne/Becker muscular dystrophy.
3. Refer those with a history of potential genetic/syndromic and chromosomal disorders as well as congenital anomalies, intellectual disability, stillbirth, sudden death, and other major health concerns such as cardiomyopathy, epilepsy, hearing loss, autism, and psychiatric disorders to a genetics clinic (Find a Clinic through CAGC: https://www.cagc-accg.ca/?page=225 ).
4. Offer genetic counselling to women/families identified as being at risk of transmission of an inherited condition.
5. When both reproductive partners are identified as carriers of the same autosomal recessive condition, promptly refer them for formal genetic counseling.

• Individuals or couples who are planning a family
• Individuals with personal or family history of a genetic condition and are concerned about passing it to their children
• Individuals of ethnicities with higher incidences of specific genetic conditions (e.g., Tay Sachs disease in the Ashkenazi Jewish and certain French-Canadian populations)
• People who are adopted or unaware of their family history
• Individuals with a family history of consanguinity (couples related by blood) or from communities where this is prevalent

• This Expanded Carrier Screen can be performed at any time prior to or during pregnancy
• The test can be performed on one or both members of the couple, at the same or different times
• Results are available within 2 to 3 weeks of receiving the blood or saliva sample at the testing lab*

*Timing estimates do not include time required for physician appointments, requisitions, consent signatures, sample collection, statutory holidays, or courier/shipping times

• Provides important information for family planning
• Helps with decision making and/or enables better preparation for baby’s arrival
• Flags conditions that could present in your child, whether or not they have been present in your families
• Enables you to access appropriate care (eg: find an appropriate specialist before delivery, access prenatal diagnosis like a chorionic villus sampling [CVS] or amniocentesis)
• Allows one to pursue in vitro fertilization, egg or sperm donation, or adoption with confidence
• Combines 289 separate DNA tests into one – minimizing the number of tests you need to take
• May be covered by provincial and private healthcare plans

Reports are sent to healthcare providers only. LifeLabs Genetics will not share results directly with patients.

Results documentation includes the following:

• A results summary, an estimate of reproductive risk, the affected gene(s), interpretation from a geneticist, a description of the detected potential disease (including prevalence, treatments, and prognoses), the methodology used (sequencing of exons relevant to the conditions tested), limitations of the screen, and suggested next steps
  • Test results usually indicate a positive or negative result. Please note that it is very common to be a carrier of something.
• Post-test genetic counselling summary: Genetic counselling is highly recommended when you receive a positive result. We include over-the-phone, post-test genetic counselling by a certified genetic counsellor at Invitae. Genetic counsellors are available to help support both the physician and the patient.

Sample Report: Individual Report (Positive Carrier Shown)

Invitae utilizes next-generation sequencing technology to screen for mutations in genes relating to 289 genetic conditions.

Click here to review the full list of diseases screened.

The accuracy, sensitivity, and specificity of this test are each >99%.

This screening test is conducted and fully supported by Invitae. Invitae has published a comprehensive set of research materials and publications on the test.

See References tab for more information.

1. ACOG: Carrier screening in the age of genomic medicine. Committee Opinion No. 690. Obstet Gynecol. 2017; 129(3):595-596. PMID: 28225420
2. ACOG: Carrier screening for genetic conditions. Committee Opinion No. 691. Obstet Gynecol. 2017; 129(3):e41-e55. PMID: 28225426
3. The Norton & Elaine Sarnoff Center for Jewish Genetics
4. Jewish Genetic Disease Consortium