Tag Archives: Genetic testing

Taking the guesswork out of genetic testing

A genome is the total of an individual’s genetic material. The genome consists of chromosomes made from very long strands of DNA. Each human has 23 pairs of chromosomes. Half are inherited from the mother and half from the father.

Susan Locke

Susan Locke

Chromosomes are organized into many subunits; the subunit is called a gene. There are 30,000 to 50,000 genes in an individual’s genome. The specific combination of genes that an individual has makes up his/her genetic identity known as a genotype.

By 2003, scientists were able to identify every gene in a human’s body. Scientists then began to look at the genes to try to pair them with the medical problems that they cause. There are many diseases that are thought to be caused by alterations (mutations) in DNA. These alterations can occur spontaneously or be inherited.

Some of the diseases with a genetic component include Alzheimer’s disease, breast cancer, ovarian cancer, colon cancer, leukemia, lymphoma, bone marrow disorders and others.

There are seven main reasons that genetic testing is performed: clinical testing to determine current or future disease; pharmacogenomics used to assess therapeutic drug treatment; identity testing (also known as “DNA testing”) used for criminal investigations or forensic studies; parentage testing (paternity testing); tissue typing for transplantation; cytogenetics (chromosome analysis, often performed on pregnant women); and infectious disease testing to determine how much viral material is still in the body after treatment.

Questions arise about the use of home genetic testing, such as “23andme.” The test can tell you if your odds of getting a certain condition are better or worse than the general population. The results you receive from this should be reviewed with your doctor. Data from 23andme can be helpful in its assessment of how a person may metabolize certain drugs.

Your results from a testing service like this should be carefully evaluated. Even if your results indicate that you possess a certain version of a gene, it does not mean that you will develop the disease.

These tests may tell you the chance of developing a certain genetic disorder, but not conclusively that the disease will develop. When a test detects a problem gene, it also cannot predict how severely the person will be affected if he or she develops the disorder.

Many diseases are a result of the interaction between genetics and environment. For example, lifestyle plays an extremely important role in who will develop heart disease. It is important to ask your physician about steps you can take to mitigate risk factors associated with any potential disorders.

There are a few other factors to consider before deciding whether to get genetic testing. There is a psychological component to testing. While having a negative test can be reassuring, a test indicating that you have a gene that predisposes you to an increased risk of a disease could be psychologically traumatizing. On the other hand, it could also lead to positive changes in lifestyle. Legally, it is possible that the results of the genetic testing could be used to determine insurance coverage.

If you do get genetic testing, the most important thing is to work with an expert to understand your test results. Most doctors are not trained to interpret these results. Genetic counselors and/ or a geneticist can help with the interpretation and implications of these complicated tests.

SUSAN LOCKE is Healthnetwork Foundation’s medical director.

HEALTHNETWORK is a Legatus membership benefit, a healthcare “concierge service” that provides members and their families access to some of the most respected hospitals in the world. One Call Starts It All: (866) 968-2467 or (440) 893-0830. Email: help@healthnetworkfoundation.org

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Genetic testing: Are these your mother’s genes?

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

Susan Locke

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.

HEALTHNETWORK is a Legatus membership benefit, a healthcare “concierge service” that provides members and their families access to some of the most respected hospitals in the world. One Call Starts It All: (866) 968-2467 or (440) 893-0830. Email: help@healthnetworkfoundation.org