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ACMG Issues Guidelines on Sequencing for Dx, Screening Purposes

NEW YORK (GenomeWeb News) – The American College of Medical Genetics last night released a policy statement and guidelines for the use of genomic sequencing for diagnostic genetic screening applications.

The guidelines cover how clinical whole-genome and whole-exome sequencing should be applied, distinguishing between cases where the technology is applied to diagnose a specific condition and when it is used as a screening purpose on asymptomatic individuals. It also asserted that the guidelines are applicable to sequencing for clinical purposes, not research.

In a statement, ACMG said that it recognizes that "genomic sequencing approaches can be of great value in the clinical evaluation of individuals with suspected germ-line genetic disorders," and there are already "instances in which genomic sequencing approaches can and should contribute to clinical care."

The organization also distinguished between returning results directly associated with the patient's phenotype or clinical condition and secondary findings or results generated from screening asymptomatic individuals.

For secondary findings, or returning results to asymptomatic individuals, "it is critical that the standards for what is reportable be high to avoid burdening the health care system and consumers with what could be very large numbers of false positive results," it wrote. By contrast, "a lower threshold for reporting is appropriate" for returning "diagnostic results that are clearly related to a patient's phenotype or clinical condition."

ACMG said whole-genome or whole-exome sequencing should be considered as a diagnostic test for individuals when the phenotype or family history data strongly implicate a genetic etiology, but the disorder is unknown and a specific genetic test is not available; when a patient presents with a defined genetic disorder with a high degree of genetic heterogeneity, making multiple single-gene tests less practical; when a patient has a likely genetic disorder, but available tests have failed at diagnosing the disorder; and when a fetus has a likely genetic disorder, but available tests have failed to diagnose it.

Prior to testing, ACMG recommends patients and families receive genetic counseling and be informed about the expected outcomes, likelihood of finding incidental results, and what types of results will be returned. Labs performing the tests should have clear policies related to disclosing secondary findings, and patients should also have the option of not receiving certain results.

Additionally, patients should be informed if a laboratory's institutional review board has approved a protocol that allows variants of unknown significance to be used for further research, and patients should consent to this use of their data.

The test itself, and every component of it, including the bioinformatics and interpretation, should be performed in a lab directed by a board-certified individual with broad medical genetics and genomics training, ACMG said.

Regarding what results it recommends returning, ACMG said that test results could include variants known to be associated with the patient's condition; novel variants whose "genetic, biological, and pathological features" indicate that they are likely involved with the patient's phenotype; and secondary findings not associated with the patient's condition, but that are known to be associated with a phenotype.

ACMG has different recommendations for whole-genome or whole-exome sequencing done not for diagnostic purposes, but as a screen of asymptomatic individuals. In these instances, it stresses that the threshold for determining which results should be returned should be "significantly higher" than when the technology is used for a specific diagnostic purpose.

Additionally, it said that individuals should be informed of the "virtual certainty of finding variants of unknown significance."

While many in the field assume that everyone will eventually have their genomes sequenced at birth, the ACMG's current position is that sequencing should not be used as a first-tier approach for newborn screening. Whole-genome or whole-exome sequencing should also not be used as a method for prenatal screening, it wrote.

However, whole-genome or whole-exome sequencing could be considered for preconception carrier screening to "focus on genetic variants known to be associated with significant phenotypes in homozygous or hemizygous progeny," ACMG said.

ACMG acknowledged that the field is rapidly evolving and said that its recommendations would likely be revised over time.

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