External Link - Source: SF Gate
There are no systematic studies of how often the direct-to-consumer results and third-party analyses are wrong. In one small study, Ambry Genetics — a lab certified to do medical testing — looked at 49 samples sent in by physicians whose patients had been told that they had disease-causing mutations by third-party interpreters. Ambry found that 40 percent were wrong. In addition, some genetic variations classified by second companies as threatening actually were benign.