Controversial multibillion-dollar health startup Theranos just got a huge seal of approval from the US government

Theranos, the blood-testing company founded by Elizabeth Holmes and valued at $9 billion dollars, received FDA clearance today for its herpes test, the company announced.

The approval marks an important step for Theranos, which has come under fire for operating in secret, releasing few details about the way their tests - which use a small amount of blood from a finger-prick - actually work.

"The FDA cleared its Herpes Simplex Virus 1 test, but more importantly, the underlying system that test is run on - which includes Theranos' 'finger stick' technology, its patented Nanotainers (used to collect minuscule amounts of blood), and Theranos' groundbreaking analysis model that can produce results in as little as 24 hours," wrote John Griffin, a spokesperson, in an email.

The company has always maintained that while it resisted publication in peer-reviewed journals in order to protect its proprietary information, it would seek out clearance from the FDA to prove to the public that their tests were effective.

"The FDA, which is the ultimate arbiter of safety and efficacy - of high quality tests that are proven to work - is the gold standard, and Theranos wants its tests to be the best and safest for its patients," the company told us in April. "We have called for an unprecedented level of review with the FDA, something we are not obligated to do. We've been submitting all of our tests to them and are committed to continuing to do so."

To receive clearance for the herpes test, which costs $9.07, Theranos submitted data from 818 subjects and said in its release that their test's results "demonstrated 100% agreement with the results provided by CDC."

In June, a clinical biochemist argued in a journal that the company's "claims of superiority over current systems and practices are speculative, at best." Applying for FDA clearance on such tests remains voluntary (though that rule that might change soon).

That means Theranos went above and beyond to validate their tests - or at least one of them - something that might help to beat back the steady stream of critics. The technology still has not been subjected to formal peer review, and the details of how it works remain secret. But the FDA approval is an important step towards validating the company's technology - and Holmes' multibillion-dollar idea.