Carrier screening is a genetic test that determines if an individual carries a gene for certain inherited disorders. It helps prospective parents understand their chances of having a child with a specific genetic condition, informing family planning decisions. This process analyzes an individual’s DNA to identify gene mutations linked to various inherited diseases.
The Purpose of Carrier Screening
Carrier screening identifies individuals who carry a gene for a genetic condition without showing symptoms. Many genetic conditions are autosomal recessive, meaning a child must inherit a mutated gene from both parents to develop the disorder. If only one parent is a carrier, their child typically will not have the condition but could also be a carrier. For example, if both parents are carriers for cystic fibrosis, each child has a 25% chance of inheriting both mutated genes and developing the condition.
A “carrier” possesses one copy of a gene mutation for a disorder, usually remaining healthy because their unaffected gene copy compensates. While some genetic conditions show a higher frequency within specific ethnic groups, such as sickle cell anemia in individuals of African descent or Tay-Sachs disease in Ashkenazi Jewish populations, current recommendations suggest carrier screening for all individuals, regardless of background. Common conditions included in most carrier screening panels are cystic fibrosis, spinal muscular atrophy, and Fragile X syndrome.
The Carrier Screening Process
Carrier screening begins with a discussion with a healthcare provider, such as an OB/GYN or a genetic counselor. During this consultation, patients learn about screening options, the conditions tested, and what results might signify.
Following the consultation, a biological sample is collected for analysis, usually a blood draw or sometimes a saliva sample. The collected sample is then sent to a specialized laboratory for genetic analysis. Labs analyze the DNA within the sample to detect specific gene mutations.
Results are typically available within a few weeks. Once ready, they are communicated back through the healthcare provider who ordered the test, allowing for a discussion of the findings and any next steps.
Bay Area Specific Testing Options and Providers
In the Bay Area, individuals seeking carrier screening have access to major hospital systems and specialized genetic testing laboratories. Prominent academic medical centers like UCSF Health and Stanford Medicine offer comprehensive prenatal and genetic services. Kaiser Permanente also offers carrier screening as part of their prenatal care.
Beyond hospital systems, several leading genetic testing companies, many with a significant presence or headquarters in the Bay Area, perform the laboratory analysis. Natera, based in Austin, Texas, with laboratory facilities in San Carlos, California, offers carrier screening. Invitae, which has joined with Labcorp, provides a broad range of genetic testing services, including carrier screening. Myriad Genetics is another established company offering hereditary cancer, prenatal, and oncology genetic testing.
These specialized laboratories process samples ordered by healthcare providers. BillionToOne also offers a carrier screen as part of its Unity Screen. Patients typically have their doctor order the test, with the sample then routed to one of these specialized genetic testing laboratories.
Understanding Your Test Results
After carrier screening, results fall into two categories: “negative” or “positive.” A “negative” result indicates the individual is not a carrier for the specific conditions screened. This suggests a very low chance of passing on those genetic conditions to offspring.
A “positive” result means the individual is identified as a carrier for one or more screened conditions. Being a carrier does not mean the individual will develop the condition; it means they carry one altered gene copy. If one partner receives a positive result, testing is usually recommended for their reproductive partner.
If both partners are found to be carriers for the same genetic condition, there is an increased chance their child could inherit the condition. Genetic counselors interpret results, explain risks, and discuss reproductive options. These options might include in vitro fertilization with preimplantation genetic testing or prenatal diagnosis.