Consistency of Direct to Consumer Genetic Testing Results Among Identical Twins
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Abstract
Purpose
To evaluate the consistency of 3 commonly used direct to consumer genetic testing kits.
Background
Genetic testing kits are widely marketed by several companies but the consistency of their results is unclear. Since identical twins share the same DNA, their genetic testing results should provide insight into test consistency.
Methods
42 identical twins (21 pairs) provided samples for three testing companies. Outcomes were concordance of ancestry results when i) twin pairs were tested by the same company and ii) the same participant was tested by different companies. Concordance of 8 self-reported traits with 23andMe genetic analyses were also examined.
Results
Concordance of ancestry results when twin pairs were tested by the same company was high, with mean percent agreement ranging from 94.5%–99.2%. Concordance of ancestry results when participants were tested by two different companies was lower, with mean percent agreement ranging from 52.7%–84.1%. Concordance of trait results was variable, ranging from 34.1% for deep sleep and detached earlobes to 90.2% for cleft chin.
Conclusion
The consistency of consumer genetic testing is high for ancestry results within companies but lower and more variable for ancestry results across companies and for specific traits. These results raise questions about the usefulness of such testing.
