Expanded carrier screening: counseling and considerations
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REVIEW
Expanded carrier screening: counseling and considerations Teresa N. Sparks1 Received: 9 March 2019 / Accepted: 25 October 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract 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.
Introduction The primary goal of carrier screening is to identify asymptomatic individuals who carry variants associated with genetic diseases, in order to inform about the risk of having an affected child. The chance of an individual being a carrier for a genetic disease is dependent in part on ethnic background and family history, with some populations having a greater baseline prevalence of certain diseases. However, genetic variants can also occur de novo, and it is well known that genetic diseases are not isolated within certain populations (ACOG Committee 2017a, b; Grody et al. 2013; Edwards et al. 2015). Genetic carrier screening during pregnancy was introduced in the 1970s, beginning with the hemoglobinopathies. Since that time, the approach to carrier screening has expanded to include additional genetic diseases such as Fragile X syndrome, cystic fibrosis, Canavan disease, familial dysautonomia, Tay Sachs disease, spinal muscular atrophy,
* Teresa N. Sparks [email protected] 1
Division of Maternal–Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, 550 16th St, Box 0132, San Francisco, CA 94143, USA
and many others (ACOG Committee 2017a). Prenatal carrier screening has traditionally been focused on the detection of a select number of genetic diseases, based on patient-reported ethnicity and family history. However, limitations of this approach include that genetic diseases are not isolated within certain populations, and in the setting of increasingly multiethnic populations, it is challenging to accurately estim
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