The blood test is a cornerstone of modern medicine. In many cases, it provides evidence that turns a bundle of symptoms to a treatable diagnosis. It's also inconvenient at best, painful at worst, and expensive.

The Silicon Valley company Theranos has an alternative—instead of a hypodermic needle and multiple vials of blood, Theranos technology uses a finger prick like the one diabetics use to measure their blood sugar. With just a few milliliters of blood Theranos can test for hundreds of things, from cancer biomarkers to cholesterol counts, illegal drugs to infectious diseases. What's more, many of the tests are cheap. And in at least one state, the system doesn't require a visit to a doctor's office or a lab. But Theranos has been slow to deploy its system.

Now things are starting to pick up. On Thursday the US Department of Health and Human Services gave the company a 1Clinical Laboratory Improvement Amendments waiver1 for a single finger-prick blood test, for type 1 herpes simplex. But that CLIA waiver does much more than approve one test—it also covers Theranos' complete system, hardware and software underpinning the entire diagnostic suite. That means that Theranos' partners, places like Capital BlueCross, Amerihealth Caritas, and the Cleveland Clinic, can install Theranos tech in place instead of having to send samples back to the company's Silicon Valley headquarters for testing.

And earlier in July, the FDA declared that same finger-prick herpes test was just as effective as the current version, the one with needles. Then Arizona made it legal to get a blood test without a doctor’s permission, on your own initiative.

Taken together, these developments mean Theranos is on its way to reinventing the field of clinical chemistry—that's blood work. And that has some scientists worried. While Theranos has touted the fact that the FDA says its tests work as well as traditional diagnostics, the company hasn't been forthcoming about how the tests work. So physicians are asking if it's enough for Theranos to be cheaper and faster when they don't know—can't know—how the company gets its results.

Better, Faster Tests

Today two companies dominate the diagnostic blood test business: Quest Diagnostics and LabCorp. As far as price is concerned, Theranos is already winning. Quest and LabCorp tests can cost...well, that depends—on your hospital, your insurer, on the day of the week. Diagnostic tests—despite being pretty much the same everywhere—don't have any official pricing. Many Theranos tests, on the other hand, cost less than $10, and the company posts its prices openly. Quest did not respond to requests for comment for this story, and LabCorp declined to comment altogether.

Theranos also wants to be fast. Like, wecantellyouifyouhaveherpesinamatterofhours fast. Back when anyone using a Theranos kit had to ship samples back to California for analysis, results were slow. Now that Theranos can distribute testing technology to all its partners, that's fixed. Patients at any of Theranos' partner institutions can walk in, get a finger-prick, and get their results.

In fact, pretty soon those patients might not even need a doctor's note to get that test. Theranos' CEO Elizabeth Holmes has repeatedly stated her desire to put blood tests into patients hands. The company declined to make her available for this story, but in 2014, she told WIRED:

There are a billion tests done every year in the United States, but too many of them are done in the emergency room. If you were able to do some of those tests before a person gets checked into the ER, you’d start to see problems earlier; you’d have time to intervene before a patient needed to go to the hospital. If you remove the biggest barriers to these tests, you’ll see them used in smarter ways.

That kind of access has already begun. In Arizona, a new law (co-authored by Theranos) cuts out the middle medic. People there can walk into a Walgreens—another Theranos partner—and get any of the tests the company offers, without a physician even knowing about it.

This doesn't drive the medical community as insane as you'd think. "I’m in favor of open access for the patients themselves. Once available, the patient should not wonder about the results, if not have access to them," says David Koch, a clinical pathologist at Emory University and president of the American Association of Clinical Chemistry. "The concern is that you need help in interpreting those results and knowing what to do next."

Yes-or-no tests are great for finding out if you have herpes or your kid is on meth, but that can get a little trickier when you’re talking about more complex conditions. For example, if a man with prostate cancer has his prostate removed, his levels of Prostate-Specific Antigen should drop below detectability. If they come back, says Stephen Master, director of clinical chemistry at Cornell Weill Medical College, it signal that he has leftover prostate cells, and those may or may not be cancerous. "But all that depends on if you have a suitable baseline," Master says. Establishing that baseline can be difficult, even for experienced physicians using established tests. All of which means that test results often require expertise to figure out their meaning.

I asked Theranos if the company had a plan to provide counseling or otherwise educate people who used their tests. A spokesperson responded by pointing me to this quote from this press release: “The Theranos model is physician-centric. Our goal in providing more accessible, less expensive, and less painful diagnostic tests is to enable individuals and physicians to better engage early when interventions can be most effective.”

That's noble, but seems a little at odds with an op-ed Holmes wrote after the Arizona law passed. "Direct access to laboratory tests ushers in a new era of individual empowerment to take control of our own health," she wrote, "to work with our physicians to prevent disease and detect it early, instead of treating illness after it has taken hold." So...people will get the tests they want and then go to the doctor? It's unclear how Theranos envisions this working.

Getting Physcians on Board

The bigger question is whether Theranos can find a way to work with physicians who are still skeptical of their technology. Theranos hasn’t released any data or methodology showing how their blood tests work. In an email, a Theranos spokesperson said that the data from the FDA trial that declared the finger-prick herpes test as effective as the industry standard is available in the agency’s summary. And that's true. It is. Those 23 pages have a lot of numbers and tables. But they are all summaries, results, averages. The company provides no comparisons showing how individual blood samples lined up against each other, no scatterplots of antibody counts, nothing quantitative that scientists can use to verify the results for themselves.

"Normally a company or individual, they would publish their investigations and techniques, present facts at meetings," Koch says. "They should be contracting with clinical labs to do studies to show that the results from their technology, to show that those results are equivalent with what’s been happening in blood testing for the last 50 years."

So why hasn't Theranos done that? Other coverage of the company has said that the company is reticent for intellectual-property reasons.

The fact is, both Koch and Master told me they think some big, disruptive change has been a long time coming to clinical lab testing. And Master says that while there are some outright hostile members of his community, most seem baffled about why the company doesn't just trust existing patent laws, and let the medical community vet its technology. “The issue is that we laboratory physicians and scientists have also seen many of the things that can go wrong with medical testing: interventions that lead to unnecessary surgeries, assays that give false pregnancy results in some patients, drifts in performance over time that affect treatment decisions, and others,” he says.

This happens with long established tests, with data that has been in the literature for years. “So when someone says ‘We won’t talk about our technology or tell you what we’re doing, but trust us because we have a CLIA-certified lab,’ I think that tends to raise concerns,” Master says.

On the other hand, those concerns may be moot. Arguably, if more states pass laws like Arizona's, physicians will be out of the loop entirely. People will go get blood tests on their own, and Theranos will have no need to bring doctors on board. At all. If the FDA says the tests work, problem solved, right? “It’s a step in the right direction,” says Koch. To scientists, no diagnostic test—not even the FDA's—is as good as raw data. But the biggest disruption Theranos may bring to clinical lab testing might be that scientists' opinions don't matter as much as they used to.

1Correction: 2:28pm ET July 21 2015. This story originally said Theranos had been issued a CLIA certification. The company already had their certification (it's what allowed them to use their finger prick tests in the lab). The waiver lets them install their testing equipment with their partners.