Theranos chief executive Elizabeth Holmes.  (GLENN CHAPMAN/AFP/Getty Images)

This story has been updated.

The secretive blood testing company Theranos has gone on the defensive in recent weeks, saying it's being picked on because its technology and approach are so radical.

“This is what happens when you work to change things,” Theranos chief executive Elizabeth Holmes said on CNBC’s “Mad Money" after the Wall Street Journal raised questions about the company's technology. “First, they think you’re crazy, then they fight you, then you change the world.”

It's true that disruptive technologies are often met with resistance, and Theranos is boldly plowing into a world where two large laboratory testing companies, Quest Diagnostics and Laboratory Corp. of America, have billions of dollars of precious turf to protect. Holmes is connecting her company to a deep and powerful narrative about inventors who are dismissed until their genius is suddenly obvious when she says Theranos is doing something so cutting edge no one recognizes its potential.

But how novel is Theranos' approach?

1) Faster tests, with less blood

A key part of Theranos' claim to novelty is using less blood and doing tests rapidly. Eleftherios Diamandis, head of clinical biochemistry at Mount Sinai Hospital in Toronto, said that there are at least 10 companies that are also using a "Theranos-like approach:" using small volumes of blood to get rapid results.

"A lot of other companies have caught up and probably surpassed them, so I just don’t see what it is that they have that is revolutionary," Diamandis said. "I just don’t get it."

Abbott Laboratories' i-STAT, a handheld analyzer that's been around for more than a decade, laid the groundwork. A medical professional places 2 to 3 drops of blood (that must be drawn from a vein) on a testing cartridge, inserts the cartridge into the i-STAT, and in a matter of 10 minutes or less can measure a subset of 25 different markers in blood, ranging from potassium to hemoglobin. The device is commonly used, at 1 in every 3 hospitals in the U.S. according to the company, and there are more than 50,000 analyzers worldwide.

It's not alone.

Alere, a diagnostics company, makes a testing device that requires only small volumes of blood that can come from either a finger or a vein.  Alere's epoc Blood Analysis system, which received FDA clearance in 2006, requires only 92 microliters of blood -- or about 2 drops -- and can measure 11 markers, including carbon dioxide, sodium, glucose and calcium. The test takes about a minute after the sample is inserted.

That doesn't mean the space isn't ripe for disruption. Currently approved devices may require blood from a vein instead of a finger stick. They may require more blood. Many of the tests can only measure a limited number of markers, and the tests may be more expensive.

But, Diamandis said, it shows that at the moment, Theranos is far from alone -- or even ahead.

"They [Theranos] didn’t monopolize this field," Diamandis said. "There are some companies now, very sophisticated, doing the thing Theranos has promised."

Theranos currently offers a single herpes test using its proprietary technology, but has said more than 120 others are on the way through the FDA. In a statement, the company said, "Theranos has an efficient business model, including low overhead and a proprietary, innovative scientific process that allows us to offer tests at much lower costs."

2) Democratizing health

This summer, Arizona enacted a law allowing consumers to order any lab tests without a physician's oversight. This is a key part of Theranos’ revolutionary strategy and a big part of how it planned to alter the health care system, by giving patients direct access to tests.

But more than half of all states already allow patients to request at least some blood tests without a prescription. And diagnostic heavyweights have already given direct-to-consumer testing a shot, according to Jondavid Klipp, publisher and editor of the trade newsletter, Laboratory Economics.

More than a decade ago, Quest Diagnostics began offering blood tests directly to consumers. In 2002, it announced a partnership with CVS and began offering a dozen tests, including for cholesterol, diabetes and sexually transmitted diseases, without a prescription in retail pharmacies in Florida and Ohio. It partnered with dozens of Stop & Shop Pharmacies in Connecticut. Its tests were available in some Giant Food Stores.

The marketing for the service, called "QuesTest," may sound familiar to anyone who has been paying attention to Theranos:

"The QuesTest service taps directly into an important megatrend that's impacting the healthcare world -- more empowered consumers choosing to take control over their health," Hughes R. Bakewell, Jr., vice president for consumer health at Quest Diagnostics, said in a press release announcing the CVS partnership in 2002.

The service was quietly shut down in 2006, according to an article in DarkDaily:

“The QuesTest program and these retail… outlets-were highly chronicled as the beginning of a new era in healthcare! Without the need to see a physician, consumers could use the QuesTest program to order their own laboratory tests, have their blood drawn, and receive secure results online, or by mail. … Apparently the hard-core group of consumers motivated to order and pay for their own laboratory tests was limited.”

Quest's competitor, LabCorp, opened centers in 20 Duane Reade pharmacies in New York City in 2006. Klipp went in 2007 to a busy pharmacy in Manhattan to have a test done. The phlebotomist said that about 10 patients came per day.

In a statement, the company responded that Theranos' combination of business model and technology will lead to lower-cost testing and increased access for patients.

Consumer needs and demands do change -- witness the rapid rise of the smartphone, a gadget that didn't even exist 20 years ago. Theranos' decision to post its price list on its Web page is seen as truly groundbreaking by industry watchers. But Klipp said he had not yet seen much evidence that consumer demands to pay for and order their own tests are taking off. He said the two direct-to-consumer lab tests that have been successful are pregnancy tests and drug tests.

3) The actual technology Theranos uses has still not been explained

Theranos has called its technology 'groundbreaking,' but it's unclear to most people outside the company how it works.  A number of well-known companies and health care leaders who have been named as Theranos partners at various times, including Cleveland Clinic, Pfizer, and GlaxoSmithKline, have said they are not currently using the technology.

"In order to compete in this space, in order to disrupt a staid industry dominated by two behemoths, there are some parts of our technology that we do not discuss in order to protect our Intellectual property. We don’t keep these parts of our technology a secret from our regulators," the company said in a statement.

Theranos garnered early criticism from some outspoken physicians because it had not been transparent about either how its technology worked or what evidence it had that it did, a crucial question in medicine.

When the company received FDA clearance for one of its more than 200 tests this summer, outside physicians were encouraged by the move, but still called for the company to publish its methods and results in peer-reviewed journals.

Diamandis, who published an article raising questions about Theranos technology in the journal Clinical Chemistry and Laboratory Medicine in June, said that he called the company back then to try and find out more about how the tests work. He asked for Holmes or one of the scientific leaders of the company to respond to technical questions about its tests. He asked if a scientific representative of Theranos would participate in a panel discussion that could appear in a scientific journal.

"They said they don’t talk to outside people," Diamandis said.

This week, Theranos indicated that would change.

"We were never against that, I just always believed that if FDA decision summaries came out one-by-one with our data, that actually that would be so much more transparent a model," Holmes said at a presentation at the Cleveland Clinic. "But that is O.K., we can publish our data so we are doing that."

A previous version of this story incorrectly described the amount of time the Alere epoc Blood Analysis Test takes. It takes less than a minute.