Walgreens was considering a partnership with Theranos Inc. when founder Elizabeth Holmes arrived at Johns Hopkins University in the spring of 2011. She brought with her a machine she said could test tiny samples of blood for dozens of conditions and thick binders of data to show its accuracy.

A Hopkins scientist told her that his researchers needed to put the device in their Baltimore laboratory to verify the technology on Walgreens’ behalf, and Holmes agreed to provide one, say people familiar with the meeting.