The Dirty Secret of Genetic Testing: We're Still Not Sure What "Normal" Looks Like

Getting a full readout of your entire genetic sequence promises to radically alter how we monitor our health, providing advanced warning of cancer and other diseases we may suffer and our chances of passing on those ailments. Clinical genetic testing firm Illumina is valued at nearly $23 billion, for example, while direct-to-consumer offering 23andMe is at about $1 billion. Meanwhile, the price for so-called whole genome sequencing has dropped to about $1,000.

But such whole-genome sequencing currently over-promises in several ways. One of them is a false sense of what constitutes a "normal" genome with which to compare someone's results. (The U.S. government's National Institutes of Health provides a narrow, widely used model.) The promise is best if you're white, and drops off fast for other ethnicities, like people of African origin. That’s because we simply don't have easy access to enough reference genomes, from a big enough variety of people, to understand the range of normal. Nor is there much willingness for companies that analyze genomes to look at all the varieties that are out there...