By Turna Ray
The use of microarray-based genotyping to predict disease risk does not provide medical benefit beyond traditional classifiers such as personal medical history and family health history, researchers from Scripps Research Institute reported in a study published in Genetic Epidemiology this week.
The study, led by Cinnamon Bloss, a Scripps Genomic Medicine researcher, enrolled more than 3,000 individuals who received genetic testing for 15 conditions through Navigenics' Health Compass service. Study participants also self-reported their personal history and family history for these same conditions. The researchers then evaluated the extent to which the genetic risk estimates provided by Navigenics were associated with individuals' personal and family history for these illnesses.
"Results of these analyses suggest that for a subset of five conditions with relatively high heritability and for which we had reasonable statistical power to detect an effect, Navigenics’ estimated lifetime risk estimates were significantly associated with [family history] and [personal history] status," Bloss and colleagues wrote. Of these five, for two conditions highly represented in participants' family and personal histories – Graves disease and type 2 diabetes – Navigenics' genetic risk estimates were "significantly associated" with individuals' personal history of the diseases over and above family history, gender, age, and ethnicity.
However, when the team assessed the "added value" of the genomic test by assessing the change in the area under the receiver operating curve based on genomic testing as compared to traditional disease factors alone, "the net reclassification based on the addition of the Navigenics estimated lifetime risk estimates did not achieve statistical significance for either condition," the study authors wrote.
Based on these findings, Bloss and colleagues concluded that such genetic tests are as effective — but not more effective — as family and personal history in assessing disease risk, and that these services may be medically useful to consumers only when information about traditional disease risk factors, such as family history, is not available.
Bloss told PGx Reporter that a specific real-world scenario where consumer genetic tests may be useful for gauging disease risk is when individuals are adopted.
On the whole, these study findings confirm the criticisms of some genetics researchers, healthcare regulators, and public health officials who feel that consumer genetic testing has no clinical advantage over currently available methods of gauging disease risk.
Muin Khoury, director of the Centers for Disease Control and Prevention's Office of Public Health Genomics, has often said that family history is a more informative and cheaper way of determining predisposition to diseases than DTC genome scans. The Office of Public Health Genomics last year issued a video warning against the limited utility of DTC genetic testing, and urged people instead to take a good family history (PGx Reporter 8/11/2010).
Although the Scripps study initially set out to gauge the clinical utility of genetic testing data sold directly to consumers, Navigenics has since changed its business model. The company previously marketed its gene scan service directly to consumers online, but after state and federal health regulators took issue with marketing such tests without the involvement of a physician, Navigenics moved away from the DTC model and now markets to health plans, employers, and physician groups.
The study participants included Scripps Health co-workers and their family members, who received genetic testing at a subsidized rate. Earlier this year, Bloss and colleagues reported data from a study involving the same cohort, which investigated whether genetic data influenced consumer behavior. Results from that study showed that DTC genetic testing does not lead to significant changes in behavior or anxiety.
According to the study authors, the strength of the latest analysis is that it is a prospective assessment of family and personal health history in a real-world, non-clinical setting, with a patient sample "unselected for any disease or trait."
In a separate analysis of 44 people in a clinical setting, Cleveland Clinic researchers compared disease risk assessments from Navigenics to individuals' family history for developing breast, prostate, and colon cancer and found low concordance between family history and genetic risk. Overall, for cancer risk assessments, the Cleveland Clinic study found that family history and genetic test results agreed on the subjects' risk categories 46 percent of the time (PGx Reporter 3/30/2011).
The Scripps authors noted that one of the weaknesses of their most recent study is that participants were highly educated and earned more than the median income level in the US, and as such were not representative of the broader population. They add, however, that this cohort is likely representative of the type of consumers who currently have access to genomic tests.
Furthermore, the researchers found Navigenics' lifetime risk estimates to be significantly associated with family and personal history in only five out of 15 conditions — shedding little light on the value of the service for those diseases.
"There are likely a few explanations for why we saw statistical associations for only five out of 15 of the conditions we assessed," Bloss told PGx Reporter. "One major one was likely due to low statistical power to detect an association in our cohort, which is related to the fact that for some conditions we had very few participants who endorsed a family or personal history.
"Conditions for which we had adequate power tended to show an association," Bloss added.
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