Gaucher Disease Screening vs. Testing
Gaucher disease affects up to 6,000 people living in the United States. This rare disorder results from certain genetic mutations that occur on the GBA1 gene. In fact, more than 400 possible mutations can be present on this gene, and while some are more common than others, all can lead to the development of Gaucher disease.
Gaucher disease is a genetically-linked autosomal recessive disorder. A person who has one gene with the genetic mutation for Gaucher disease is a carrier of the disease. A person who has two genes with the genetic mutation actually has the disease itself. If both your mother and father are carriers for the disease — meaning they both have one mutated copy of the gene that causes Gaucher disease — you’ll have a 50 percent chance of being a carrier, a 25 percent chance of having Gaucher disease and a 25 percent chance of being unaffected (not a carrier nor have the disease).
People diagnosed with Gaucher disease come from all ethnic groups and backgrounds, but most carriers are of Ashkenazi Jewish descent. Approximately 1 in 10 Ashkenazi Jews are carriers for this genetic mutation.
With advances in medical technology, it’s now possible to screen and test for genetic mutations associated with Gaucher disease. This can help you determine your Gaucher disease carrier status. If you begin to show symptoms — or if you have two parents who are carriers or a parent with Gaucher disease — further testing can determine whether you actually have the disease. However, it’s easy to get confused about what each of these assessments are and when doctors use them to diagnose Gaucher disease.
What is genetic screening?
“Genetic screening, often referred to as carrier screening, looks more at carrier status to determine whether someone carries a mutation rather than whether someone actually has a certain genetic disease,” explains Kara Woolgar, Lysosomal Nurse Program Coordinator at Phoenix Children’s Hospital. Doctors rely on screenings, which are broader in scope than more specific genetic tests, to identify common genetic mutations within certain high-risk ethnic groups. Broad carrier screenings are less expensive than specific genetic tests. If you’re a member of a high-risk ethnic group, including Ashkenazi Jews and people of French Canadian ancestry, your doctor may choose to perform genetic screening to identify your carrier status for many inherited genetic mutations that cause common diseases, such as Gaucher disease, cystic fibrosis, and Tay-Sachs disease.
However, there are some limitations to genetic screening. These tests usually only screen for the most common genetic mutations within a certain ethnic population, so there could be mutations that haven’t yet been identified. Also, because screening tests concentrate more on carrier status, they don’t identify as many mutations on genes as a more comprehensive genetic test does.
Fortunately, genetic screening for Gaucher disease is a simple process that uses a saliva or blood sample to determine carrier status. When you undergo screening, you’ll most likely be asked to provide a saliva sample for testing. Technicians send the sample to a laboratory certified in genetic screening and testing, and you typically receive results within four to six weeks. Then, your results are reviewed, and if appropriate, you’ll speak with a genetic counselor who can provide more information about your carrier status and help you plan for your family’s future.
How is genetic testing different from screening?
Genetic testing, commonly known as an enzyme assay, also identifies genetic mutations that cause Gaucher disease, but these tests focus on single genes or certain parts of DNA that are associated with the condition. Like screening tests, genetic testing uses saliva or blood samples to sequence entire genes, like the GBA1 gene. These tests are specifically used for diagnostic purposes – to identify mutations. If you have symptoms of Gaucher disease or a strong family history of the condition, your doctor will most likely recommend genetic testing.
“With genetic testing, we’re looking more at the specific gene that causes Gaucher disease – and whether there are mutations present. These tests use complete gene sequencing, and are much more thorough than genetic screening tests,” says Woolgar. In addition to this type of genetic testing, diagnostic tests, including beta-glucosidase leukocyte (BGL) tests, can help confirm a Gaucher disease diagnosis.
How can NGF help?
October is Gaucher Disease Awareness Month and to highlight the importance of genetic screening and testing, NGF, in partnership with JScreen (a community-based public health initiative from Emory University School of Medicine), is proud to sponsor a carrier screening initiative wherein a genetic carrier screening test kit is mailed to your home. From now through December 31, 2017, the first 500 people who register to participate will receive a home saliva collection kit that screens for more than 200 genetic diseases, including Gaucher disease.
Also, NGF is now partnered with the Greenwood Genetics Center to launch a pilot diagnostic initiative specifically for people who have siblings with Gaucher disease and have yet to have genetic testing. If your sibling has the disease, your doctor can order a specific genetic test, called an enzyme assay, that helps determine whether you also have Gaucher disease. You’ll need to provide a blood sample for this test, but other than this simple step, there’s no cost to you. If you’d like more information on obtaining an enzyme assay test kit and requisition form, you or your doctor can contact Samantha Rubenstein, NGF’s Senior Patient Advocate and Optimal Health Advisor.
Uncertain about genetic screening or testing? Keep in mind that learning your carrier status for diseases like Gaucher can help you make more informed decisions about family planning. “It’s important to get screened and tested early, because the results can help you plan for the future. If you have Gaucher disease type 1, we can start treatment early which may help prevent symptoms or control them better. It’s very important to be evaluated by a Gaucher disease specialist. That way, they can monitor your condition and determine when treatment is appropriate,” says Woolgar.
- Gaucher Disease. National Organization for Rare Disorders. https://rarediseases.org/rare-diseases/gaucher-disease/
- Gaucher Disease Carrier Status. National Gaucher Foundation. http://www.gaucherdisease.org/gaucher-diagnosis-treatment/testing/carrier/
- The 5 Most Common Ashkenazi Genetic Diseases. National Gaucher Foundation. http://www.gaucherdisease.org/blog/5-common-ashkenazi-genetic-diseases/
- Testing for Gaucher Disease. National Gaucher Foundation. http://www.gaucherdisease.org/gaucher-diagnosis-treatment/testing/
- A Review of Gaucher Disease Pathophysiology, Clinical Presentation and Treatments. International Journal of Molecular Sciences. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5343975/
- Why are some genetic conditions more common in particular ethnic groups? U.S. Department of Health and Human Services. https://ghr.nlm.nih.gov/primer/inheritance/ethnicgroup