Theranos founder Elizabeth Holmes still has yet to take advantage of the Cleveland Clinic's offer to test the blood diagnostic technology developed by her embattled Silicon Valley start-up, said Dr. Toby Cosgrove, CEO of the highly rated hospital.
"I'm disappointed. I hoped that this [testing] would happen in the near future," Cosgrove told CNBC's "Squawk Box" on Thursday. He added: "The promise of that technology is huge. Whether it works or not we have to see."
"We don't have a financial investment. I don't have a personal investment. But we have offered to test her machine anytime that she's willing to do that. We haven't progressed to that so far," Cosgrove said.
Amid questions that the tests don't work as advertised, Theranos faces a criminal investigation into whether it misled investors, and inquiries from multiple federal agencies.
Theranos has also voided two years of results from its proprietary Edison machines, which the company claims are able to perform a range of sophisticated screenings with just a few drops of blood.
Earlier this month, drugstore chain Walgreens announced an end to its relationship with Theranos, another blow for a company once lauded for its potential to disrupt the entrenched laboratory diagnostics industry with fast, less-invasive blood tests.
Theranos, valued at one point at more than $9 billion, had made 50 percent owner Holmes the world's youngest female billionaire. Forbes, which tracks the fortunes of billionaires around the world, this month reduced its estimate of the net worth of Holmes from $4.5 billion to zero.
A spokesperson for Theranos, responding to the Forbes report, said: "As a privately held company, we declined to share confidential financial information with Forbes. As a result, the article was based exclusively on speculation and press reports."
Palo Alto, California-based Theranos traces its roots to 2003, when Holmes at 19 years old founded the company. She dropped out of Stanford University a year later.
In an interview with "Squawk Box" in September 2015, Holmes said she was motivated to build her company due in part to a "traumatic fear of blood," and the thought that using smaller samples would encourage people to get tested.