(Cox News Service) -- Doctors often withhold treatment information from their patients because the services are not covered by insurance, according to a survey conducted by the American Medical Association.

The results of the survey, which was conducted in 1998 and 1999, were analyzed in Tuesday's edition of the medical journal "Health Affairs."

The article's lead author, Dr. Matthew Wynia, director of the Institute for Ethics at the American Medical Association, said he believes the survey results are still valid because the pressures on doctors in deciding what services to recommend and what treatments to provide "have probably increased over the last five years or four years."

The decision not to mention certain services or treatments is a violation of numerous medical codes of ethics, including the American Medical Association's, Wynia said. Such practices "in the extreme, can constitute fraud," the article said.

"Honesty is just a fundamental principle of physician-patient interaction," Wynia said, adding that if a patient discovers that information has been withheld it can harm the patient's trust. "In the long run, it is imperative that physicians adhere to this ethical principle," he said.

The survey found that 31 percent of doctors who mailed back responses admitted not offering "useful care to patients because of health plan coverage rules at least 'sometimes.' " Of those, 35 percent said they were withholding information more frequently than they had five years earlier.

Because the survey involved doctors admitting to unethical practices, the article noted that if there were errors, it would be in "under-reporting" the withholding of information.

While ethics codes require doctors to disclose "medically appropriate treatment alternatives, regardless of cost," the article notes that "a lot of doctors are nervous about describing medically indicated ... care that isn't covered" by insurance.

In many cases, doctors may withhold information about alternative drugs that treat the same ailment, Wynia said.

Larry Akey, spokesman for the Health Insurance Association of America, said "we always encourage medical providers to contact health plans and health insurance companies about a procedure that they perceive to be medically necessary. Even if it's outside the insurance contract, most of the time the insurance companies find a way to pay."

William S. Custer, a professor in the Insurance Department at Georgia State University, said doctors have always factored a patient's ability to afford treatment into their medical advice

"Doctors have done that since the days of Marcus Welby. They understood what the patient could afford and offered services that would fit what they could afford," Custer said, noting that more recently doctors feel that insurance companies are determining what a patient can afford.

"In and of itself, this is not an ethics issue. It's in the specifics of a case where there might be an ethics issue," he said.

Among the rationales physicians offered for withholding information was a desire to avoid patient pressure to "game the system" by manipulating insurance rules.

Although doctors fought vigorously in the 1990s against medical plans that imposed "gag orders" that prohibited them from discussing certain alternative services, the article argues that "some physicians appear effectively to be 'gagged' by coverage restrictions."

Physicians with a large number of poor patients -- generally covered by Medicaid -- were more likely to withhold information because of coverage restrictions, the article said, noting that physicians argue, "why offer a useful medical service to someone who cannot afford it?"

American-born physicians were more likely than foreign-born physicians to withhold information. The article suggested that foreign-born physicians may be more comfortable accepting restrictions on care while "American-born physicians and their patients might expect insurance coverage to be broad and deep."

The article concludes that patients need to be informed of relevant medical alternatives and doctors need to "reinforce their ethical stand on this issue."

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