Health insurers are increasing their screening of applicants for infection with the human immunodeficiency virus (HIV) that causes AIDS and are denying coverage to those who test positive, according to a study to be released today by the congressional Office of Technology Assessment.

The survey of 62 insurance companies, including the largest in the industry, showed that 29 percent said they consider sexual orientation in underwriting, a violation of antidiscrimination guidelines adopted in 1986 by the nation's insurance commissioners.

Also included in the survey of individual health-insurance policies were 16 health maintenance organizations (HMOs), which provide members care for a fixed annual fee, and 15 Blue Cross/Blue Shield plans.

With few exceptions, the OTA found that "if you test positive, you will be denied health insurance," said Jill Eden, director of the study conducted with help from industry trade associations. "Insurers are very interested in knowing whether someone's at risk for AIDS, and they've obviously all mobilized."

Although companies are moving to limit their financial exposure to acquired immune deficiency syndrome, warning that the disease threatens the industry's viability, its impact has been small, according to a report last month by the Health Insurance Association of America (HIAA). The group represents 85 percent of the nation's insurance carriers.

In 1986, that report said, AIDS cases amounted to an estimated 0.3 percent of claims paid by group health policies and 0.7 percent for individual policies.

The OTA's findings were similar. Although one Blue Cross plan insured 3,000 people with AIDS, most insurers reported fewer than 10 AIDS cases. "A significant number of companies weren't even able to say what their AIDS claims had cost," Eden said.

Debbie Chase, manager of media relations for the twin industry trade associations, the HIAA and the American Council of Life Insurance, said "we know that the numbers do look small" but they are "no indication of what's going to be going on in future years" as the AIDS toll rises.

Chase said the industry finds it "rather troubling that any company would be found to use information about sexual orientation in underwriting."

The 1986 guidelines, approved by the National Association of Insurance Commissioners and adopted by seven states, say "sexual orientation may not be used in the underwriting process or in determining insurability."

Drafted by a committee that included gay rights activists and insurance industry representatives, the guidelines were designed to bar discrimination against homosexuals.

Four of the 16 HMOs surveyed said sexual orientation is considered before an applicant is accepted for membership. Figures were unavailable for Blue Cross insurance plans.