Federal Government to Expand Definition of AIDS : Health: It will now include all persons with severe immune system damage, which would increase the official caseload estimate.

The federal government announced plans Thursday to expand the definition of AIDS, a change expected to add thousands of people to the official estimate of the caseload in this country.

The Centers for Disease Control, which tracks epidemics, said that it intends to broaden the definition on Oct. 1 to include all AIDS-infected individuals who show evidence of a severely damaged immune system as measured by the level of CD4 cells in their blood.

CD4 cells, also known as T4 helper cells, are the primary targets of the human immunodeficiency virus that causes AIDS.

“This will add tens of thousands of cases to the official estimates of the disease,” said Dr. James O. Mason, assistant secretary for health, in an interview. “It will also more accurately reflect the extent of the disease in the country.”

The new AIDS definition will include those individuals whose blood contains 200 or fewer CD4 cells per cubic millimeter, even if they show no overt symptoms of the disease. A normal CD4 level is about 800 to 1,000.

Currently, CDC’s definition requires the presence of specific HIV-related symptoms, such as opportunistic infections and other ailments known to result from an impaired immune system. Although such symptoms no longer will be necessary, individuals whose CD4 counts have fallen to 200 “are most likely to be severely ill or disabled and in greatest need of medical and social services,” the agency noted.

The planned change, which CDC has the authority to implement by itself, does not signify that AIDS has become more prevalent in America. Instead, it means that many cases will be counted much earlier than they would have been under current practices.

Based on the current definition, a total of 182,834 people have developed AIDS in the United States since the beginning of the epidemic in 1981. But the CDC estimates that about 1 million Americans are infected with the HIV virus, and many of these probably will be classified as having AIDS under the new definition.

Ultimately, the change could increase the level of public funding of various AIDS programs in cities and states. It could also allow AIDS patients to receive disability benefits sooner, because some agencies have relied on the CDC definition to determine eligibility.

The CDC has come under fire in recent years from AIDS activists and others for failing to include certain conditions--particularly those unique to women--as part of its definition. Critics have charged that numerous AIDS-infected individuals have been denied benefits, health care and access to clinical trials as a result.

The only initial resistance to the change came from within the CDC itself. Mason acknowledged that the agency had been reluctant to tamper with the current definition--which was established for surveillance purposes when the disease was first identified--because it “messes up your baseline for comparison from past to future.”

But he said that the time has come for AIDS to be tallied “just like every other disease” for which laboratory measures are available. “As soon as you get good laboratory parameters for any disease, you go to those parameters,” Mason said.

The CDC said that the new definition “will make interpretation of trends in incidence and characteristics of cases more difficult” but “will provide a better estimate of the health care needs of severely ill persons with HIV infection.”

Although the original definition was intended for epidemiological purposes only, some agencies, including the Social Security Administration, have used it to determine whether an individual may receive benefits under disability or other programs.

A source in the Department of Health and Human Services said that the Social Security Administration currently is “reviewing and making changes” in AIDS eligibility requirements. Moreover, the agency already has moved away from using the CDC guidelines to determine whether an individual is too disabled to work and therefore eligible to collect disability, the source said.

“We couldn’t use the T-cell counts as our definition anyway,” he said. “There are (HIV-infected) people who have counts of 1,000 who are unable to work, and others who have counts of 200 or less and are working full time.”

Medical experts and others praised the CDC action, although some noted that it raises troubling questions.

Jeffrey Levi, director of government affairs for the AIDS Action Council, said that changing the definition “has a simplicity that is attractive, while also capturing most of the morbidity associated with HIV.” But he added that “it poses many practical challenges.”

For example, he said, many individuals with HIV infection lack access to CD4 testing and, even with access, “the relative quality of testing varies from lab to lab.”

Further, Levi said, “does one meet the case definition with one count below 200--or several? Does one stop having CDC-defined AIDS if, through early intervention therapy, one’s CD4 count goes above 200?”

Dr. Mervyn F. Silverman, president of the American Foundation for AIDS Research, said that the change should remove “impediments to access to health care, clinical trials or medications, and benefits--this should help a great deal.”

Dr. Robert T. Schooley, an AIDS specialist who heads the department of infectious diseases at the University of Colorado Health Sciences Center, also praised the move.

“It’s long overdue,” he said. “The disease is clearly due to progressive destruction of the immune system. This will now allow us to define the disease by the major effect of the virus--and not by having to wait until an individual develops some arbitrarily defined--and potentially undiagnosed--infection.”