23andMe said my most elevated risks about double the average for women of European ethnicity were for psoriasis and rheumatoid arthritis, with my lifetime odds of getting the diseases at 20.2 percent and 8.2 percent. But according to Genetic Testing Laboratories, my lowest risks were for you guessed it psoriasis (2 percent) and rheumatoid arthritis (2.6 percent).
For coronary heart disease, 23andMe and G.T.L. agreed that I had a close-to-average risk, at 26 to 29 percent, but Pathway listed my odds as above average.
In the case of Type 2 diabetes, inconsistencies on a semantic level masked similarities in the numbers. G.T.L. said my risk was medium at 10.3 percent, but 23andMe said my risk was decreased at 15.7 percent. In fact, both companies had calculated my odds to be roughly three-quarters of the average, but they used slightly different averages and very different words to interpret the numbers. In isolation, the first would have left me worried; the second, relieved.
Medical ethicists and other experts have a different kind of worry about results like these: a lack of industry standards for weighing risk factors and defining terminology.
The risk is in the eye of the beholder standard is not going to work, said Arthur L. Caplan, director of medical ethics at the New York University Langone Medical Center. We need to get some kind of agreement on what is high risk, medium risk and low risk.
Several other problems may account for my discrepancies. The genetic testing that these three companies offer is premised on reading segments of DNA called SNPs (pronounced snips), for single nucleotide polymorphisms. But these segments, which have been linked to diseases in research studies, vary among people.
Scientists have identified about 10 million SNPs within our three billion nucleotides. But an entire genome sequencing looking at all three billion nucleotides would cost around $3,000; the tests I took examined fewer than a million SNPs.
Imagine if you took a book and you only looked at the first letter of every other page, said Dr. Robert Klitzman, a bioethicist and professor of clinical psychiatry at Columbia. (I am a graduate student there in his Master of Bioethics program.) Youre missing 99.9 percent of the letters that make the genome. The information is going to be limited.
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23andMe declined to comment for this article. Jim Bentley, the chief operating officer of General Genetics Corporation, which owns G.T.L., said test results should be interpreted with professional guidance: Because of the complexity of genetic testing results and other factors that have a role in determining the long-term potential health risks a person may face, such as environmental conditions and personal health habits, G.G.C. requests its customers provide information that would allow us to send the results of our predisposition test to a physician.
The chief medical officer of Pathway, Dr. Michael Nova, said: Pathway Genomics is accredited by the College of American Pathologists, and accredited in accordance with the U.S. Health and Human Services Clinical Laboratory Improvement Amendments of 1988. As such, we are held to a higher standard for report accuracy than our unaccredited competitors.
