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ACMG Updates Carrier Screening Recommendations for Autosomal Recessive, X-Linked Conditions

NEW YORK – The American College of Medical Genetics and Genomics on Tuesday released new guidelines on carrier screening tests, recommending a new tiered and equitable approach for offering carrier screening to all individuals during pregnancy or preconception.

In a paper published in Genetics in Medicine entitled "Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG)," the college said that the joint guidelines it published in 2015 in collaboration with other professional organizations on expanded carrier screening remain largely applicable today.

But the updated guidelines take more recently published information into consideration and closes gaps in the previously published paper, "while acknowledging technological advances in sequencing and the need for equity and distributive justice of genomic technologies," the ACMG said in a statement.

Improving patients' understanding of their risk will also allow them to make informed reproductive decisions, which is the established metric for clinical utility of population-based carrier screening, the ACMG working group said in the paper. Further, standardization of screening will facilitate testing consistency.

Jeffrey Dungan, co-author of the new paper and chair of the ACMG Professional Practice and Guidelines Committee, noted that a tiered structure in defining gene sets for analysis could help clinicians and patients to communicate better with each other. He also added that the ACMG has now created a set of 113 genes, both autosomal recessive and X-linked, that should be considered as a standard offering to preconception and prenatal patients.

In updating the guidelines, the authors asked questions they believed were important for clinicians and reproductive-age patients to consider as part of the carrier screening process, such as what screening approach should be offered to patients and what considerations clinicians and genetic counselors should emphasize during pre-test and post-test counseling.

Importantly, the ACMG said, professional organizations have an obligation to define the conditions appropriate for carrier screening. Until now, molecular testing labs have mostly performed this task, resulting in screening conditions that are not uniform across labs.

The consensus group recommended establishing a tier-based system of carrier screening in which all pregnant patients and those planning a pregnancy should be offered Tier 3 carrier screening. The authors defined Tier 3 screening as carrier screening for conditions with a carrier frequency of 1 in 200 or more, which includes X-linked conditions.

They also wrote that education and counseling are critical in carrier screening, and that informed decision-making ideally should be a part of preconception care. Knowledgeable and appropriately trained healthcare professionals should inform patients of the risks, benefits, and consequences of carrier screening, before and after testing, and patients should be supported to make informed and autonomous decisions including the decision to not undergo carrier screening, the working group said.

"This process is time- and labor-intensive and new models need to be developed to train non-genetics providers and to counsel patients," the authors added. "Over time, we believe clinicians will become comfortable with the concepts, specific genes, and their associated conditions. Importantly, molecular testing laboratories are called on to adapt and innovate to keep carrier screening costs low and throughput high."

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