Nearly one-third of doctors don't discuss all available medical options with their patients, citing coverage limitations imposed by health insurance companies, a new study finds.

Lead author Matthew Wynia and his colleagues surveyed 700 U.S. doctors, asking them how often they decided not to offer a "useful service to a patient because of health plan rules." The term "useful service" was not defined.

Twenty-three percent of the doctors surveyed responded "sometimes," while another 8 percent answered "often" or "very often," reports CBS News.

"Patients aren't getting the whole story," the network quotes Wynia, who is director of the Institute for Ethics at the American Medical Association but whose research was done independent of the AMA. The practice of withholding information based on a patient's insurance coverage "in essence, cuts the patient out of the decision making process," he adds.

The findings are reminiscent of a 1990s controversy when some managed-care companies barred doctors from discussing medical options that weren't covered by the companies' health plans. Most of the managed-care firms dropped the requirement after a public outcry, the CBS report says.