Nov. 5, 2010 -- The widely held belief that you can always rely on family may be especially true when it comes to your risk for certain diseases, new research shows.
Researchers led by Dr. Charis Eng, chairman and founding director of the Genomic Medicine Institute of the Cleveland Clinic, found that a thorough family history better predicted the risk for developing certain cancers than genomic screening did.
"Evaluation of family health history still remains to be the gold standard in personal disease risk assessment," Eng said in a news release.
Genomic screening isn't the same as genetic testing. Genomic screening involves evaluating portions of a person's genetic makeup to determine whether there are genetic variants that put people at higher risk to develop particular diseases or traits. In genetic testing, people are screened for the presence of an entire gene known to cause a disease.
Eng and her colleagues assessed 44 people's risk for developing breast cancer, prostate cancer and colorectal cancer by obtaining a complete family health history and also by using a direct-to-consumer personal genomic screening tool. They presented their findings at the annual meeting of the American Society of Human Genetics.
A comparison between the two methods showed that they did not often place people in the same risk category for the three kinds of cancer. Researchers also found that personal genomic screening did not identify nine people who were found to be at high risk for colon cancer because of a previous family history.
Experts Agree Family History Is Essential
"Study after study has shown that a well-taken family history can be one of the most powerful predictive factors for preventative health and health maintenance," said Dr. Kandamurugu Manickam, a geneticist at Ohio State University's Center for Personalized Health Care in Columbus.
Family Histories Misunderstood
"It has always been my contention that the well-taken family history is the most sophisticated genetic test," said Dr. Ronald Bachman, chief of the Department of Genetics at Kaiser Permanente Oakland Medical Center in California.
In addition to helping assess disease risk, doctors say knowing a patient's family history can help offer insight into how someone will respond to certain treatments.
Dr. Marjorie Bowman, professor of family medicine and community health at the University of Pennsylvania School of Medicine in Philadelphia, said, "I told a patient never to take a statin drug as her brother went into marked liver failure within a few days of taking a statin drug; a rare event that seems highly likely to have a significant genetic component."
Although they cost little or nothing to do and patients can easily obtain the information, one barrier to family histories is the time constraints primary care doctors are under. While they agree that family histories are important, there's often not enough time to get them.
Another problem with family histories is that primary care doctors don't always know how to take a thorough family history, according to medical specialists. They also say that even electronic medical records do not allow for a proper medical history and subsequent assessment of risk.
"One issue raised in this study is the importance of educating health care providers in risk assessment based on family history and in strategies for communicating these family history-based risk results," said Dr. F. Sessions Cole, chief medical officer in the Division of Newborn Medicine at the St. Louis Children's Hospital.
Doctors Skeptical of Personal Genetic Screens
"My sense is that most direct-to-consumer testing is used by a subset of the population who are both Internet-savvy and who can afford to pay out-of-pocket for these rather expensive tests," said Dr. Paul Fernhoff of the division of medical genetics at Emory University School of Medicine in Atlanta.
Dr. Bruce Korf, president of the American College of Medical Genetics, said, "There is also potential for misuse and-or misinterpretation of results, particularly given the lack of professional counseling that accompanies the results in some cases, and most of the results do not lead to clear actions to modify risk."
Korf also said there isn't much known about many genetic variants that may be involved in disease risk, so it's difficult to determine how clinically useful these personal screening tests are.
Doctors also say that while people are more aware that the tests exist, they don't think many people are using them, mostly because of the cost. Most of those who do, they say, are concerned about their risk for breast cancer.
Earlier this year, the U.S. Food and Drug Administration requested that five companies offering direct-to-consumer genetic testing submit the tests for scientific review to make sure they are accurate. Navigenics, the company that manufactures the personal genomic screening tool used in Eng's research, said in response that they are happy to cooperate with the FDA. But calls to Navigenics to respond to the the findings of Eng and her colleagues were not returned.
Another company that offers genetic testing, 23andMe, stands by their consumer tests.
"We are confident in our service's accuracy and reliability. It is widely accepted that the technology we are using is sound," the company said in its blog, The Spittoon.
In response to previous criticism that results from personal genetic tests often conflict with family history information, 23andMe said, "This is a criticism that could be said of any risk prediction."
Despite their skepticism, medical experts say personal genomic screening may someday prove its value.
Eng, who led the research comparing family history to personal genomic screening, said the results show more testing is needed to determine how useful personal screening can be.
"[P]ersonal genomic screening tests could potentially be more effective and accurate if combined with family health history information and used as a complementary tool for cancer risk assessment," Eng said.
Korf said, "I think that the data on risk of disease based on genomic screens will improve, and may become a component of routine medical care if the validity of these tests can be established and actions defined that can help people to respond to instances of increased risk."