Expanded carrier screening with prepair+ is a more comprehensive carrier screen designed for couples, prior to pregnancy. This screen tests the biological mother and the biological father to determine their chance of having a child affected with one or more inherited genetic conditions. Testing covers over 250 different conditions. Most of these are autosomal recessive or X-linked conditions.
Most people who have expanded screening will find out they are carriers of at least one condition. This type of information can be relevant for other members of your family.
Types of conditions included in expanded screening
prepair+ screens for 289 inherited genetic conditions. The conditions vary in severity and the way in which they affect people.
Some conditions affect only one part of the body, while others affect multiple systems and organs. For some conditions, there is significant variability within the condition. This means it may be difficult to predict how a child might be affected.
For some of the conditions, early diagnosis and treatment can improve outcomes and/or mitigate (reduce) symptoms. But for many conditions there is no treatment available or the treatment may be very difficult for the child and their family.
The types of conditions screened can be grouped broadly into these categories:
Conditions which shorten life expectancy
These are severe conditions which reduce the life expectancy of affected individuals, most people with the condition do not live past childhood or early adulthood.
Conditions which cause intellectual disability
The level of intellectual disability caused by a particular condition varies from mild to severe. Mild intellectual disability may mean that a child needs extra support in learning, but will usually be able to do things for themselves. Severe intellectual disability may mean that a child never learns to walk or talk.
Conditions which cause physical disability.
Some conditions cause vision or hearing loss. Other conditions affect the organs or limbs, meaning that they do not work the way they should.
These conditions are caused by problems with the brain. This can be changes to the structure of the brain. Or problems with the way the brain sends messages to the rest of the body. These conditions may worsen over time.
Some conditions affect the way the body breaks down different chemicals. These conditions are often treatable if diagnosed early. If untreated, the build up of chemicals can cause damage to various parts of the body.
What is the test process
Expanded carrier screening is a couple based test performed using saliva samples collected from both biological parents at the same time. Saliva collection kits and instructions are mailed to you and inlcude reply postage.
Below is an overview of the test process.
Understanding autosomal recessive and X-linked inheritance
These are both types of inheritance patterns. They describe how genetic conditions can be inherited.
Children can be born with recessive genetic conditions if both parents are carriers of the same condition. Carriers usually do not experience any health problems themselves. If both parents are carriers, there is a 1 in 4, or 25% chance, of having a child affected by the condition. There is a 50% any child will be a carrier like the parents.
View a fact sheet about autosomal recessive inheritance - NSW Centre for Genetics Education
These conditions are carried on the X chromosome. If the biological mother is a carrier of an X-linked condition, there is a 50% chance any sons will be affected and a 50% chance that any daughters will also be carriers.
View a fact sheet about X-linked inheritance - NSW Centre for Genetics Education