Blog | Tuesday, April 3, 2012

QD: News Every Day--Doctors issue guidelines for genetic testing


Rising adoption of whole-genome sequencing has prompted a medical society to issue guidelines about their appropriate use and interpretation in an effort to ease concerns over false-positives and their ensuing harm to patients.

Meanwhile, other genetic scientists who looked at 24 common diseases said that knowing one's entire genome doesn't offer that much insight into disease.

First, new guidelines from the American College of Medical Genetics and Genomics should guide clinicians about who would benefit and when. Tests should be interpreted by a health provider "who is familiar with the enormously complex and voluminous data that is obtained from genomic sequencing."

The policy statement states that genomic sequencing should be considered when:
--the phenotype or family history data strongly implicate a genetic etiology, but the phenotype does not correspond with a specific disorder,
--a patient presents with a defined genetic disorder that demonstrates a high degree of genetic heterogeneity, making whole-genome or whole-exome sequencing more practical,
--a patient presents with a likely genetic disorder but specific genetic tests available for that phenotype didn't results in a diagnosis, and
--a fetus with a likely genetic disorder in which specific genetic tests available for that phenotype fails to make a diagnosis.

Pre-test counseling should be done by a medical geneticist or an affiliated genetic counselor and should include a formal consent process, according to the guidance statement. Participants should be counseled regarding the expected outcomes of testing, the likelihood and type of incidental results that could be generated, and what results will or will not be disclosed.

Test results can include gene variants relevant to the patient's condition, unrelated gene variants implicated in a patient's underlying phenotype, or gene variants unrelated to the condition that led to the testing ("secondary findings"). There should be clear policies that address how secondary findings are communicated to patients, the policy document states. Patients should be given the option of not receiving secondary findings.

Asymptomatic individuals interested in whole-genome or whole-exome sequencing for health screening should receive both pre-test and post-test counseling from a trained medical geneticist and/or affiliated genetic counselor. They should know the potential risks and benefits of such testing "and the virtual certainty of finding variants of uncertain significance."

And, the threshold for determining which results should be returned to individuals seeking screening should be set significantly higher than that set for diagnostic testing due to the much lower chance of disease in such individuals.

But, said another group of scientists, while a complete genomic "blueprint" can signal higher risk for some diseases, some genetic conditions are so rare that it doesn’t make sense to sequence everyone. And, people with genetic predispositions still need to lead a healthy lifestyle, they added.