Diagnosis and Testing
Is there newborn testing for Alagille syndrome?
Newborn screening does not test for Alagille syndrome. However, if a newborn starts showing signs of liver problems, his/her doctor may order testing for Alagille syndrome if there are other symptoms as well.
More Diagnosis and Testing Content
Is there more than one type of test for Alagille syndrome?
Since there are multiple types of genetic changes that can cause Alagille syndrome (ALGS), there are multiple genetic tests your doctor might order to confirm a diagnosis of ALGS. Since spelling mistakes in JAG1 are the most common cause of ALGS, found in 89% of people with the condition, sequencing (or reading the gene from start to finish) of JAG1 is usually the first genetic test done. If no spelling mistake is found, your doctor might then order a different test to see if there are big pieces of JAG1 missing or added, since that is the next most common cause of ALGS. If there is still no change in JAG1 found, your doctor might order sequencing of NOTCH2 as the last genetic test. It also may be possible to order all these tests at once, but that would be up to you and your doctor to discuss.
Who else in my family should I test for Alagille syndrome?
First-degree relatives (parents, siblings, and children) should be tested for Alagille syndrome since the condition can cause very different symptoms in different people, and may not have been picked up in others until your diagnosis. If you have had genetic testing that found a JAG1 or NOTCH2 mutation, your relatives can be tested for that same mutation. If no mutation was found, other family members cannot be genetically tested. However, these relatives can be seen by doctors to look at their liver, heart, eyes, skeleton, and facial features to help determine if they have Alagille syndrome or not.
How is Alagille syndrome diagnosed?
Alagille syndrome is usually diagnosed by a doctor based on the symptoms a person is having. A diagnosis of Alagille syndrome is made if a person has a low number of bile ducts in their liver as well as at least three of the following symptoms: buildup of bile in the liver, heart defect, differences in the bones (usually the bones of the spinal column), eye changes, and characteristic facial appearance. If someone in the family already was diagnosed with Alagille syndrome, other family members with at least one of these symptoms may be diagnosed with it as well.
Genetic testing is not always necessary to diagnose the condition. Genetic testing can help let other people in the family what their chance of having a child with Alagille syndrome is.
Does it matter if you test blood versus saliva versus a biopsy for Alagille syndrome?
A blood or saliva test works well for genetic testing for Alagille syndrome. It is not necessary to get a biopsy to do this testing.
Is there prenatal testing for Alagille syndrome?
If a pregnancy is at increased risk for Alagille syndrome, prenatal testing can be done as long as the genetic change causing Alagille syndrome in the family is already known. Prenatal testing will be able to tell if the baby has the genetic change causing Alagille syndrome or not, but cannot tell how severe the symptoms will be in a baby with the genetic change.
- Alagille Syndrome. GeneReviews. http://www.ncbi.nlm.nih.gov/books/NBK1273/
How accurate is the genetic testing for Alagille syndrome?
The clinical sensitivity of the test, meaning the chance that a test will find a gene change/mutation in someone who has Alagille syndrome, is about 95%. This means that out of everyone in the world with clinical diagnosis of Alagille syndrome, 95% of them will have a gene change/mutation found on the genetic testing. In other words, 5% of people with Alagille syndrome will not have a gene change/mutation picked up by the test. False positives, meaning a gene change/mutation is found when there actually is not one, are rare.
- Leonard, LD, Chao, G, Baker, A, Loomes, K and Spinner, NB. (2014) Clinical utility gene card for: Alagille syndrome (ALGS). EJHG 22. http://www.nature.com/ejhg/journal/v22/n3/full/ejhg2013140a.html