The colonoscopy: It may be the most dreaded screening test out there, and it's the next step in KQED's PriceCheck project.

On PriceCheck, we're crowdsourcing prices of common health tests and procedures. KQED, along with our colleagues at KPCC in Los Angeles and a health cost transparency startup in New York, are asking people in California to share what they've paid for various health care procedures.

We turned to crowdsourcing because health care prices are wildly variable and opaque. It sometimes stuns people to find out there is no central database of prices. Gag clauses in contracts between doctors and insurers forbid both parties to disclose prices.

People who live in California can use this form to help bring prices into the open. Just get the explanation of benefits your insurance company sent for the colonoscopy and enter price charged, price the insurance company paid and your copay (which should be zero for a screening colonoscopy — more on that below.)

Our PriceCheck database already contains entries for colonoscopy prices, which range from $1,000 to $5000 in the Bay Area. Surprised by that range? It's in line with the price variations reported both by policy experts and our PriceCheck community for other procedures.

After we get more shared prices (usually in a few weeks), we'll report them back to you at KQED's health blog and on Shots.

Under the Affordable Care Act, colonoscopy and certain other screening tests are required to be covered at no cost to the patient. But we should all care about the wild variation in prices because as health care costs rise, health insurance premiums go up. If you have employer-sponsored health insurance, that can mean your own part of the premium will go up. Public insurance programs like Medicare and Medicaid get more expensive, too, and those are paid for through taxes.

Colonoscopy is "a messy one," says Maribeth Shannon with some irony. She specializes in market transparency and accountability at the California HealthCare Foundation.

She's not just referring to the procedure itself. Colonoscopy is messy because of the way it's billed. Here are some things to ask about before you go in for the procedure:

Screening or diagnostic: In a screening colonoscopy, a doctor threads a flexible tube with an attached camera into the colon to look for abnormalities, like a polyp. If a polyp is found, it can be removed during the procedure.

After the ACA first took effect, some patients who had polyps removed discovered that this action changed the colonoscopy from a "free" screening test to a diagnostic test, and they were on the hook for a big bill. Federal rules have since clarified that "polyp removal is an integral part of a colonoscopy" and must be included at no cost to the patient. Still, Maribeth Shannon says that "consumers should check with their health plan and ask 'what happens if a polyp is found — you're going to treat that as preventive, right?' "

Anesthesia:You might think that anesthesia would be included with the price of a colonoscopy. After all, it's not surprising that many patients would want to be anesthetized. But for quite awhile, patients were being billed for anesthesia, which by itself can run $1,000 or more.

That's what happened to Gareth Tyrnauer of Sebastopol, Calif. He was delighted when his insurer sent him a letter that said a colonoscopy would be covered 100 percent. "I'd be a fool not to do this," he recalls thinking. But after the procedure, he got a $1,200 bill — just for the anesthesia. He called his insurer's customer service to fight the bill, saying he told the representative, "I've got a piece of paper right here and it says 'it's 100 percent covered.' What part of 100 percent don't I understand?" He ultimately won.

Earlier this month, the federal government stepped in again and issued a clarification that insurers may not charge for anesthesia used in connection with a preventive colonoscopy.

In-network is key:Make sure you know in advance who is involved in the procedure, warns Dena Mendelsohn, a health policy analyst with Consumers Union in San Francisco. "Consumers should be sure to confirm that the facility where they're going is in-network and the provider they will have is in-network."

Quality: In health care, determining quality of a procedure can be as difficult as determining how much it might cost. A strong predictor of quality is volume of procedures. A doctor or facility that has high volume is likely to be doing a higher quality job. Mendelsohn says many health insurance plans have tools for their customers on their websites and sometimes that includes volume. How much is the right amount? Hard to know, she says, but consumers could compare "hundreds or thousands versus dozens."

Mendelsohn also recommends avoiding a large university medical center for a colonoscopy. "Large universities are tailored toward more complicated procedures," she says. "Since a screening colonoscopy is more routine, it's not necessarily the case that going to a large university will get you a better colonoscopy."

Other options:If you've been dreading have a colonoscopy, you're not alone. But there are other non-invasive options for colon cancer screening, including the fecal occult blood test. If you've been avoiding a colonoscopy, you may want to learn more about this option.

This story was produced by State of Health, KQED's health blog.

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