Forbes has revised the net worth of the woman it crowned America's richest self-made woman last year from $4.5 billion to nothing.

Forbes says its estimate of Elizabeth Holmes' wealth is based entirely on her 50 percent stake in troubled blood-testing startup Theranos. The company acknowledged in April that it's under investigation by several regulators and agencies following a series of reports by The Wall Street Journal in which former employees said the company's tests were unreliable. The tests use only a few drops of blood.

Theranos said the articles were inaccurate when they were published.

Forbes says its previous estimate of her wealth came from a $9 billion valuation for the company in 2014.

The 32-year-old Holmes started Palo Alto, California-based Theranos in 2003 and remains its CEO.