Medical diagnosis is not risk free
Fivethirtyeight questions some assumptions made by Theranos about the presumed benefit of cheap and easy medical diagnosis. One problem is false positives, and the more invasive diagnostic procedures they would generate. Perhaps larger is the problem that identifying abnormalities that previously went undetected gives no information on whether or not it is beneficial to treat them. As example, better tests for thyroid cancer have detected much more of a cancer that turns out to be quite common, but have not improved mortality. That said, the tests will get better and medical science will figure out which problems to chase and which to leave alone. Pushing the technology will nudge medical practice.
Regardless of coming technology, people still will need to keep their eyes open. Errors in diagnosis and in treatment sometimes are deadly.