Genetic testing: Are these your mother’s genes?

Susan Locke writes that genetic testing can help pinpoint diseases and disorders . . .

Susan Locke

Genetic testing — also known as DNA-based testing — has been an evolving technology in medicine. Different types of genetic testing are done for different reasons. Samples for genetic testing are obtained from blood, hair, skin, amniotic fluid or other tissue.

Newborn screening is the most widely used type of genetic testing in the U.S. Most newborns are screened for phenylketonuria and congenital hypothyroidism.

Predictive testing will detect gene mutations associated with disorders that occur after birth and can be beneficial in making decisions about medical care.

Pharmacogenetics is a newly evolving field to help determine what medication and dosage will be most effective for an individual.

Prior to genetic testing, it’s often helpful to meet with genetic professionals to discuss the benefits, risks and limitations of a particular test. While the physical risks involved with testing are minimal, the psychological consequences may be significant.

The results of genetic testing aren’t always straightforward, so interpretation of results must be taken in the context of family history, personal medical history, and type of genetic test. It’s also important to remember that only limited information can be provided about an inherited disease. For example, it cannot predict severity of symptoms or progression of a condition. Lifestyle and environment also play a part in an inherited disease.

For more information on genetic testing, I turned to a world-renowned genetics physician Charis Eng, MD, PhD, the founding chair of Cleveland Clinic’s Genomic Medicine Institute.

What is your opinion on Direct-to-Consumer (DTC) testing?

DTC testing provides consumers with a genetic analysis of their saliva by testing for a range of single nucleotide polymorphisms (SNPs) — DNA sequence variations — that have been loosely associated with, but never shown to be causative of, disease. These low-cost tests can be engaging, allowing consumers to investigate their heritage and network with others who share similar genealogy and disease risk. However, consumers and health-care providers alike need to understand the limitations of this testing.

When DTC tests appeared on the market, some consumers, health care providers and policy makers mistakenly believed these tests provided a genetic risk assessment equivalent to that obtained by a family health history-based risk assessment. Our research has shown that these two methods of risk predication are quite different.

Evaluation of family health history still remains the gold standard in personal disease risk assessment. A personal family health history report can be completed at little cost, and this type of information is typically readily accessible and easily gathered by the patient.

What is the role of pharmacogenetics?

Pharmacogenetics uses a person’s genetic information to predict his or her response to drug treatments. For example, warfarin (Coumadin) is widely prescribed to prevent blood clots in patients with certain heart conditions. A genetic test is available to help select the right dose of warfarin, based on a patient’s genotype.

Currently, there are more than 100 medications approved by the FDA with pharmacogenetic information on their labels. A small number of these carry a “boxed warning,” which is a warning reserved for those medications that may have serious or sometime fatal complications for people who carry a rare genetic marker. If tests show that a patient has such a marker, the physician will adjust the dose or prescribe an alternate treatment.

If you would like more information about an appointment with a genetic specialist, please contact us today.

SUSAN LOCKE, MD, is Healthnetwork Foundation’s medical director.

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