Expanded carrier screening: counseling and considerations.

The primary goal of carrier screening is to identify asymptomatic individuals who carry variants associated with genetic diseases, to inform about the risk of having a child with a genetic disease. Carrier screening can be accomplished through different approaches including ethnicity-based screening, pan-ethnic screening, and expanded carrier screening (ECS), and the decision to pursue carrier screening is voluntary. ECS takes a broad approach by screening for a large number of genetic diseases irrespective of ethnic background, and ideally is performed prior to conception. ECS has many benefits, including that it does not depend on accuracy of reported ancestry, as well as its greater yield of information that can be used for reproductive decision-making. However, there are also many important limitations of ECS to consider, ranging from the yield of unexpected information, uncertainty about the phenotype of a particular disease for which an individual is a carrier, and greater downstream costs associated with further testing and genetic counseling. Detailed genetic counseling both prior to and after ECS is essential in order for patients to understand the breadth of this approach, potential and actual results, and limitations.