The medical start-up pioneer once proclaimed America's richest self-made woman by Forbes magazine was now worth nothing, the business publication reported Wednesday.

Elizabeth Holmes founded the blood-testing company Theranos and holds 50 percent of its shares, which led Forbes to estimate her net worth to $4.5 billion.

But now Forbes revised the 32-year-old's wealth to zero, after new information came to light indicating the privately-traded business is worth only $800 million - and not $9 billion, as estimated after its valuation.

Holmes only owns common stock in the company, as opposed to preferred stock like Theranos' other shareholders. This would effectively see her empty-handed in case of a liquidation, as preferred stock holders would get their money back first.

Rise and fall of Theranos

When Theranos was founded in 2003, it caused a stir in the medical sector and media attention quickly garnered on Holmes. She set out to replace traditional blood tests with a new method, allowing doctors to perform hundreds of tests with only a single drop of blood.

But recently surfaced allegations cast doubts on whether the low-cost tests are actually accurate.

Several US agencies, including the health authority CMS, are investigating the company. In a letter, it said Theranos' practices posed a direct threat for patients' health and safety.

The US stock exchange authority SEC is also investigating Theranos for stock fraud.

mrk/uhe (AFP, dpa, Forbes)