No one looks forward to screening tests for colon and rectal cancers. But under the Affordable Care Act, patients are at least supposed to save on out-of-pocket costs for them. Coverage is not always clear, however, and despite the federal government’s clarifications, consumers still have questions.

Under the law, most health plans are required to cover a range of preventive health services without any cost-sharing by patients if the services are recommended by the U.S. Preventive Services Task Force, an independent group of medical experts. (The only exception is for health plans with grandfathered status.)

The task force recommends colorectal cancer screening for most adults starting at age 50. These tests include colonoscopy (in which a doctor inserts a flexible tube with a video camera at the end into the anus to examine the large intestine for polyps, tumors and other abnormalities), sigmoidoscopy (a similar process that examines only the lower part of the colon) and fecal occult blood testing (which examines the stool for traces of blood).

A colonoscopy is the most thorough of the screening tests and is favored by many clinicians. About half the time, polyps are discovered and removed during the test to determine whether they are cancerous. This removal can create billing problems, says Katie Keith, a research professor at Georgetown University who co-authored a report on screening colonoscopy coverage under the Affordable Care Act.

According to the study, some insurers judged that a colonoscopy with polyp removal was a therapeutic rather than a screening procedure, and subsequently billed patients for some or all of the test’s cost, which can reach $2,000 or more.

In February, the Obama administration stated that for people in group and individual health plans, polyp removal during a screening colonoscopy was an integral part of the screening test and should be covered without patient cost-sharing. However, the guidance doesn’t apply to Medicare beneficiaries.

Other screening coverage questions remain murky. What happens, for example, if someone gets a positive result on a fecal occult blood test? In that case, the task force says a colonoscopy is required to examine the colon. But insurers vary in whether they consider such a follow-up colonoscopy a separate diagnostic test, according to the report by Keith and others, including the Kaiser Family Foundation.

“In many communities, stool testing may be common because people can’t get an appointment for a colonoscopy for months,” says Robert Smith, senior director of cancer screening at the American Cancer Society, another co-author of the report. “If they have a positive stool test, they face the uncertainty of what it would cost to get the colonoscopy.”

People who are at higher risk for colon cancer because of family history or their own history of polyps also face a gray area in cost-sharing. These patients are often advised to get a colonoscopy more often than every 10 years, the recommended frequency for people at average risk. In February, the federal government clarified that high-risk patients could qualify for more frequent screening without cost-sharing.

Despite this, some patients have run into snags. Because doctors discovered three polyps during a colonoscopy five years ago, Allen Worob, 66, is considered at high risk for colon cancer. He was advised by his doctor to get a follow-up colonoscopy in five years. At first, his insurer told him that the procedure would cost him nothing if no polyps were found but that he’d owe $2,500 if a polyp were discovered. (Worob’s primary coverage is through his wife’s group health plan, supplemented by Medicare.)

Worob, who lives in Rochester, N.Y., was later told that the procedure would be covered without any out-of-pocket charge, whether or not any polyps were found. But Worob decided to wait for a letter from his insurer spelling that out before getting the test.

“Just because [the government] has clarified the law, it doesn’t mean anybody’s going to follow it,” he says. “I can’t take a $2,500 hit.”

This column is produced through a collaboration between The Post and Kaiser Health News. KHN, an editorially independent news service, is a program of the Kaiser Family Foundation, a nonpartisan health-care-policy organization that is not affiliated with Kaiser Permanente.