DNA Test Guide

By Mary Kay Radnich, Tests.com Contributing Writer

The field of genetic testing involves using a blood or other tissue sample, such as a cheek swab, to look for patterns or changes in an individual’s chromosomes, genes or proteins. The majority of genetic tests are used to diagnose genetically caused diseases or to determine the probability of an individual developing a certain disease. Genetic counseling is often provided with test results so that the patient can be more informed in the decision-making process.

Because genetic testing can reveal a wealth of information about an individual, genetic testing is also used in the fields of law enforcement forensics and genealogy, the tracing of one’s ancestral heritage.

To preserve the genetic privacy of an individual, then-President George W. Bush signed the Genetic Information Nondiscrimination Act (GINA) of 2008 into law, to prevent insurance companies and employers from using a person’s genetic test results against them.

Types of Genetic Tests

Over 900 types of genetics tests are available today. These tests fall into four broad categories:

• Disease-related genetic testing: Genetic testing can be used for diagnosing a genetically-caused illness or for determining the likelihood of an individual developing a disease or passing that gene on to future generations. This type of testing can also be performed on newborns, with counseling provided to the parents by genetic pediatricians.
• Pre-natal genetic testing: Pre-natal genetic testing is used to determine gene variations which may cause disease or handicap in babies, while they are still in the womb. Testing for Down Syndrome via amniocentesis or chorionic villus sampling are examples of pre-natal genetic tests. Again, pediatric genetic counseling is provided to the prospective parents.
• Paternity testing: This type of DNA testing is used to determine the closeness of genetic relationship between two individuals. The chance of two unrelated individuals having the same genome is at least 1 in 6 million. The similarities between two individuals’ DNA sequence is used to determine their genetic relationship, ie – parent/child, siblings, distant cousins, etc. Home test sampling kits are available for paternity testing.
• Genealogical genetic testing: Not only can genealogical genetic testing determine the closeness of relationship between individuals or family members, but it can also be used to determine one’s ancestral or tribal background, as well as ethnicity. This very popular field continues to grow thru home test kits, as more people become interested in their ancestral heritage. The home test kids enable an individual to obtain a tissue sample via a cheek swab and then send the sample to a laboratory for analysis. Some very famous family genealogical testing results are the descendants of the Thomas Jefferson-Sally Hemings union and the descendants of Niall of the Nine Hostages, a former ruler of Ireland, of which over 20% of today’s Irish are his descendants.
• Forensic genetic testing: Forensic testing is most commonly known as the sort of testing seen on television crime dramas, which links organic evidence from a crime scene to a suspect. This is but a narrow part of a very broad field of forensic genetic testing, which includes testing to identify a crime suspect or to exonerate one wrongly convicted, identify catastrophe or crime victims and to authenticate consumables such as wine or caviar. Forensic genetic testing can also be used to determine organic pollutants in air, water, soil or food, and as an aid to wildlife conservation officials and animal breeders.

How Genetic Tests Work

Organic tissue is sampled from an individual, either blood or other type of tissue, such as a scraping from the inside of the cheek. The sample is then sent to a lab for analysis of the Y-chromosome DNA (or Y-DNA), the mitochondrial DNA (or mt-DNA), other chromosomes, located in the cell’s nucleus or for a biochemical test looking at protein levels. A biochemical test is typically used on newborns.

During analysis, the location and pattern of the chromosome is compared to a standard or to another sample, to find a match or lack thereof.

Genetic Test Results

Tests result availability ranges from a few hours to many weeks, depending on the type of genetic test and the lab which is processing the test.

Results from home testing kits which are mailed to a lab usually take weeks to arrive. Many of these companies offer results through a secure website and offer a variety of follow-up counseling opportunities.

In the case of genetic testing to diagnose disease or other health conditions, results and then follow-up with your health care provider or a genetic counselor is recommended.

Preparation for Testing

There is no special preparation for the physical aspect of genetic testing, however, many individuals consult with a health care provider or genetic counselor to determine the pros and cons of genetic testing before the decision to proceed with testing is made.

Risks

It is important the genetic test in question meets the criteria for analytical validity, which is the ability of the test to accurately identify the presence or absence of a given gene, clinical validity which refers to the test’s ability to accurately predict the presence or absence of a disease and clinical utility which indicates a test’s usefulness in providing information to the patient.

Genetic testing as well as all health-related testing is subject to federal regulatory standards known as the Clinical Laboratory Improvement Amendments, as well as even tougher state-mandated laboratory standards.

Are you thinking of utilizing a genetic test? Let our DNA Directory help you.  For more on genetic testing, please read our interviews with genetic test experts Kristine Ashcraft and Dr. Michael Baird.