Consistency of Direct-to-Consumer Genetic Testing Results Among Identical Twins

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.

Genotype concordance and polygenic risk score estimation across consumer genetic testing data

“…23andMe reported 95.1% Chinese; 2.1% Filipino and Austronesian; 0.5% Indonesian, Thai, Khmer, and Myanma; AncestryDNA reported 100% China; Gencove reported 91% East Asia and 9% Southeast Asia. The general concordance regarding major contributors to ancestry and variability regarding minor contributors to ancestry is consistent with other studies showing congruent results for the major contributors to ancestry (Thompson, 2018) despite variability when considering all reported ancestral components (Huml et al., 2020).…”

“…In the foreseeable future, one needs to consider the scenario where two services provide conflicting results. Previous studies also reported that differences in the choice of SNPs on microarrays used by different companies could be an important contributor to variability in disease risk (Imai et al., 2011) and variability in self‐reported phenotypic traits versus genetic testing results (Huml, Sullivan, Figueroa, Scott, & Sehgal, 2020).…”

DNA testing information on YouTube: Inadequate advice can mislead and harm the public

“…Inaccurate test results can lead to emotional distress, unnecessary diagnostic testing, and medical intervention, which may pose risks for patients. In one study, 40% of genetic variants reported in DTC DNA raw data were reportedly found to be false positives (Tandy-Connor et al, 2018) and considerable variation has been found when comparing results from different DTC DNA companies (Huml et al, 2020). Others who have questioned the predictive validity of DTC DNA results (Friez, 2018;Huml et al, 2020;Nelson et al, 2019;Tandy-Connor et al, 2018) highlighted concerns over reliability, consistency, and accuracy (United States Government Accountability Office 2010).…”

Genetic Ancestry Testing

“…In all cases, accuracy is strongly affected by the choice of reference populations and the selection and number of SNVs, all of which vary among ancestry testing companies. Consequently, it is not unusual for different companies to report somewhat different ancestral profiles for the same DNA sample . Furthermore, many human populations have migrated considerably during their history; therefore, modern-day samples represent a static and potentially inaccurate portrayal of a region’s inhabitants in the past.…”