DALLAS, FEB. 6 -- Parkland Memorial Hospital tested 700 emergency room patients for the AIDS virus without their knowledge, the hospital's president said, an action that critics attacked as a violation of medical ethics.

The Dallas Times Herald reported in a copyright story today that the patients were tested as part of a study to determine what percentage of the population has been infected with the HIV virus that causes acquired immune deficiency syndrome.

Only those who tested positive, about one percent of those checked, were informed of the results, said Parkland President Ron Anderson.

Critics attacked the hospital's action and noted that testing patients without their consent violates the American Medical Association code of ethics.

"What's wrong with this study . . . is there was an invasion of privacy," said Ronald Bayer, associate for policy studies at the Hastings Center, a national research institute specializing in ethics.

"You should never test anybody for anything without their consent," said Arthur Caplan, director of the Center for Biomedical Ethics at the University of Minnesota.

However, Anderson defended the tests, which were sanctioned by the hospital's institutional review board and broke no laws.

Anderson said the only patients tested were severely injured and needed blood drawn for other tests. He said blood samples were coded to protect the patients' identity.

"The AMA would be happier if we did not notify people who tested positive," he said. "Maybe they don't want to face the person they test and tell them the bad news. We could let those people go on and infect their loved ones. But we feel obligated to the patients."