The Limitations of Genetic Testing
We all know from biology class that we have 46 chromosomes. We inherit half from our mother and half from our father. This makes up who we are. Doesn't it? We have heard science has discovered the gene for diabetes, fat, and alcoholism, only to then hear these discoveries didn't quite pan out. Scientists are finding that genetics is much more complicated than originally thought.
How 23andMe's Tests Work
23andMe's website states they are a "DNA analysis service" using "the Illumina HumanOmniExpress-24 format chip." This chip "consists of a fully custom panel of probes for detecting single nucleotide polymorphisms." These single nucleotide polymorphisms (SNPs) are mistakes that occur when a cell divides and copies its DNA for the second cell. Most of the time these mistakes, which are like typos, do not lead to any observable differences in people. However, some lead to differences in health or physical appearance.
The test looks at 1 out of every 3,000 letters, or nucleotide bases. 23andMe obtains raw data from its test, and then compares the results to scientific literature and its own database. The company has several publications on its website called "white papers" which explain their method for interpreting results.
One statement that is blatant in the literature is the word "assume." Their interpretations are based on numerous estimates and assumptions. They even report "very few SNPs are perfectly correlated."
Can the Results be Trusted?
So here's the rub: what if someone were to obtain medical treatment based on these assumptions and estimations? Would a surgeon perform a mastectomy based on results from 23andMe? What if a person decides to forego treatment based on the results of the test? Bloomberg author Robert Klitzman stated results between 23andMe and a competitor "were in disagreement at least half of the time on seven of 13 illnesses analyzed."
23andMe is still selling its ancestry product. DNA is becoming an interesting tool in genealogy. Several companies offer genetic services for genealogy use. These companies take the data and compare it to European databases.
The FDA considers these tests medical devices. As such, they claim oversight. It is obvious this type of testing needs to be regulated and monitored. There is also a concern with the amount of genetic data that is being collected. What is being done with the huge bank of data 23andMe has collected from its customers?
One important fact should be remembered: health conditions are caused by the combination of genetics and environmental factors. As such, one genetic test may not provide all the information needed to assess an individual's predisposition toward a particular disease. Time will show how these tests improve and how companies work together with the FDA to produce a useful, trustworthy product.