Expanded Carrier Screening and the Complexity of Implementation.

Advances in genetic technology have allowed for the development of multiplex panels that can test for hundreds of genetic disorders at the same time; these large panels are referred to as expanded carrier screening. This process can screen couples for far more conditions than the gene-by-gene approach used with traditional carrier screening; however, although expanded carrier screening has been promoted as an efficient means of detecting many more disorders, the complexities of genetic sequencing raise substantial challenges and concerns. In our practice, we have seen a number of complex cases in which only attention to detail on the part of thorough genetic counselors allowed identification of misclassified variants that could have resulted in significant patient harm. We raise issues that require urgent attention by professional societies, including: whether to endorse testing that uses sequencing compared with genotyping; required components of pretest and posttest counseling; reclassification of variants; whether obstetric health care professionals have a responsibility to assure that patients understand the iterative process of variant interpretation and how it relates to carrier screening results; and the question of rescreening in subsequent pregnancies. Implementation of expanded carrier screening needs to be considered thoughtfully in light of the complexity of genetic sequencing and limited knowledge of genetics of most front-line obstetric health care professionals.