A healthy 28-year-old with concerns about diseases in her family had three different companies check her genetic code. The discrepancies in their results were striking.
23andMe said the most elevated risks — about double the average for women of European ethnicity — were for psoriasis and rheumatoid arthritis, with lifetime odds of getting the diseases at 20.2% & 8.2%. But according to Genetic Testing Laboratories (GTL). The lowest risks were for — you guessed it — psoriasis (2%) and rheumatoid arthritis (2.6%).
For coronary heart disease, 23andMe and GTL agreed that I had a close-to-average risk, at 26-29%, but Pathway listed odds as “above average.”
In the case of Type 2 diabetes, inconsistencies on a semantic level masked similarities in the numbers. GTL. said risk was “medium” at 10.3%, but 23andMe said risk was “decreased” at 15.7% . In fact, both companies calculated 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 worry about results like these: a lack of industry standards for weighing risk factors and defining terminology.
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. “You’re missing 99.9% of the letters that make the genome. The information is going to be limited.”