Genetic genealogy testing companies aren't doing enough to make sure you understand the limitations and implications of DNA testing, says the American Society of Human Genetics (ASHG)
The organization, whose 8,000 members include geneticists, scholars, genetic counselors, nurses and others, today issued a statement with recommendations for the genetic genealogy industry.
It was prompted by the rising popularity of genetic genealogy. According to the ASHG, a half-million Americans will spend $100 to $1,000 per test this year.
ASHG faults tests designed to determine ethnic ancestry, rather than the Y-DNA tests that estimate whether you’re related to someone. "Rarely can definitive conclusions about ancestry be made beyond the assessment of whether putative close relatives are or are not related," reports the statement.
That's because such tests compare the genetic contribution from a tiny slice of your family tree against a reference database that uses DNA samples from modern-day individuals to represent populations that existed eons ago. A lot of population shifting and combination has happened since then.
No standards exist for statistical analysis and how results are reported to you, says the statement. "Perhaps the most important aspect of reporting confidence in ancestry determinations is to accurately convey the level of uncertainty in the interpretations and to convey the real meaning of that uncertainty."
As genetic ancestry testing expands to cover inherited medical conditions, ASHG is concerned patients may misconstrue the results of these often-inconclusive tests when making medical decisions.
The organization joins a growing chorus. States such as California and New York have come down on genome profiling companies including 23andMe and DNA Traits
for providing medical testing without involving individuals’ doctors.
A year ago, the New York Times doubted the accuracy of ethnic DNA tests after its reporter received varied and conflicting test results from five companies
. Bert Ely, a geneticist who helped start the African-American DNA Roots Project
with high hopes in 2000, shared his findings that most African-Americans have genetic similarities to numerous ethnic groups in Africa—making it impossible to match African-Americans with a single group.
An article in the Oct. 19, 2007, Science
magazine cited these problems:
- Limited information in companies’ reference databases might lead them to draw the wrong conclusions. (Today’s ASHG statement said these databases “reflect a woefully incomplete sampling of human genetic diversity.”)
- Some companies’ databases are proprietary, making it hard to verify customers’ test results.
- Tests trace a small percentage of a person’s ancestors and can’t pinpoint where they lived, or the specific ethnic group they might’ve belonged to.
The ASGH ancestry testing recommendations include the following:
- The genetic genealogy industry should make a greater effort to clarify the limitations of ancestry testing. Consumers must understand more about ancestry testing.
- Additional research is needed to further understand the extent to which the accuracy of test results is affected by the makeup of existing human DNA databases, geographical patterns of human diversity, chromosomal marker selection and statistical methods.
- Guidelines should be developed to facilitate explanation and counseling for ancestry testing.
- Scientists analyzing genetic ancestry test results should take into account the historical, sociopolitical and cultural contexts under which human genetics evolved.
- Mechanisms for greater accountability of the ancestry testing industry should be explored.
Part of the problem may lie in the complex science involved. The explanations are difficult for laypeople to understand (I'm a layperson, and I'll admit it); but in simplifying them for marketing materials and test reports, DNA companies may downplay the tests' limitations.
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