senior scientists how they defined an outlier, no one could give her a
straight answer. Erika and Tyler might be young and inexperienced,
but they both knew that cherry-picking data wasn’t good science. Nor
were they the only ones who had concerns about these practices.
Aruna, whom Tyler liked and respected, also disapproved of them and
so did Michael Humbert, a jovial German scientist Tyler had
befriended.
One of the validation experiments Tyler helped with involved a test
to detect syphilis. Some tests measure the concentration of a substance
in the blood, such as cholesterol, to determine whether it is too high.
Others, like the syphilis test, provide a yes-or-no answer about
whether a patient has a particular disease or not. The accuracy of those
tests is gauged by their sensitivity—the measure of how often they
correctly label someone with the disease as positive. Over a period of
several days, Tyler and several colleagues tested 247 blood samples on
Edisons, 66 of which were known to be positive for the disease. During
the first run, the devices correctly detected only 65 percent of the
positive samples. During the second run, they correctly detected 80
percent of them. Yet, in its validation report, Theranos stated that its
syphilis test had a sensitivity of 95 percent.
Erika and Tyler thought Theranos was also being misleading about
the accuracy of other Edison tests, such as a test to measure vitamin D.
When a blood sample would be tested on an analyzer made by the
Italian company DiaSorin, it might show a vitamin D concentration of
20 nanograms per milliliter, which was considered adequate for a
healthy patient. But when Erika tested the same sample on the Edison,
the result would be 10 or 12 nanograms per milliliter—a value that
signified a vitamin D deficiency. The Edison’s vitamin D test was
nonetheless cleared for use in the clinical lab on live patient samples,
as were two Edison thyroid hormone tests and a test to measure PSA,
the prostate cancer marker.
—
IN NOVEMBER 2013, Erika was moved from the immunoassay group to