Originally published January 21 2014
Genetic testing wildly inaccurate; different labs reach opposite conclusions on disease risk
by Ethan A. Huff, staff writer
(NaturalNews) If you or someone you know is considering taking a genetic test to assess future disease risk, you may be interested to know that the accuracy of such tests is hardly reliable. Writing for The New York Times (NYT), Columbia University graduate student Kira Peikoff explains how, after undergoing genetic testing using kits available from three major testing companies, her understanding of her gene-associated disease risk is even more abstract.
The reason for this is that all three tests provided different results in many major disease categories. One testing kit claimed that Peikoff has an elevated risk of developing both psoriasis and rheumatoid arthritis, for instance, with lifetime odds clocking in at 20.2 percent and 8.2 percent respectively. But another testing kit came to the exact opposite conclusions, reporting extremely low odds of 2 percent and 2.6 percent, respectively.
Similar results were observed for coronary heart disease, which Peikoff says runs in her family. One testing kit claimed that she has a close-to-average risk of developing an illness in this disease category -- "average" risk hovers between 26 and 29 percent -- while another testing kit revealed an "above average" risk of developing the disease. And the pattern repeated for many of the other diseases analyzed.
"At a time when the future of such companies hangs in the balance, their ability to deliver standardized results remains dubious, with far-reaching implications for consumers," writes Peikoff for NYT, referring to the fledgling genetic testing industry.
Genetic testing companies use varying criteria to assess disease risk
One reason for these major discrepancies is the fact that genetic testing companies tend to use different standards to assess disease risk, often resulting in vastly different risk prediction outcomes. Another factor is the sheer number of unique DNA segments present inside the body, segments that vary dramatically from sample to sample.
"Scientists have identified about 10 million SNPs (single nucleotide polymorphisms) within our three billion nucleotides," explains Peikoff, noting that each of these segments provides a different lens through which disease risk can be assessed and interpreted. "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."
One of Peikoff's professors, Dr. Robert Klitzman, agrees. In his view, using genetic testing kits, which only look at limited segments of human DNA, to assess disease risk in light of the entire human genome is like trying to read a book by looking only at the first letter of every other page. It would be impossible, using this analogy, to gather any sort of relevant information from the book.
"A small percentage of people who get tested will get useful information," says Dr. Klitzman. "But for most people, the results are not clinically useful, and they may be misleading or confusing."
Diet and lifestyle, not genes, the biggest factors in disease risk
Even if all those do-it-yourself genetic testing kits were capable of reading every single letter and word in the book, so to speak, there is still the issue of how much genes account for disease risk. Mainstream health authorities are quick to blame so-called genetic "defects" on the chronic disease epidemic that continues to burgeon in the U.S., but the truth of the matter is that genes account for as little as five percent of disease risk.
"Even if they are accurately looking at five percent of the attributable risk, they've ignored the vast majority of other risk factors," says Dr. Wendy Chung, an associate professor of pediatrics and medicine and director of clinical genetics at Columbia University.
Sources for this article include:
http://www.nytimes.com
http://www.usatoday.com
http://www.huffingtonpost.com
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