The Federal Centers for Disease Control has revised its definition of AIDS, and the change could add tens of thousands of people infected with the virus to the ranks of those considered to have the disease.
The change, to take effect in January, allows doctors to diagnose the disease based on blood levels of a kind of immune system cell depleted by the AIDS virus. That would be in addition to the opportunistic infec tions or other conditions resulting from damage to the immune system that the Atlanta-based CDC has used so far to define AIDS.
Advocates of people infected with the human immunodeficiency virus have criticized the list of illnesses that define AIDS because it did not include many conditions frequently seen among intravenous drug users and women infected with HIV, two groups increasingly affected by acquired immune deficiency syndrome.
The revision, recommended by the Council of State and Territorial Epidemiologists and endorsed by the Association of State and Territorial Health Officials, will be announced after the details of its implementation have been worked out with state and local health departments.
Many agencies, from private insurance companies to government social service offices, use the federal list to decide who automatically qualifies for AIDS-related benefits. But many of them, including the Social Security Administration, had already begun taking the cell levels into account in determining whether applicants qualified for benefits.
The new definition will include in the AIDS caseload any HIV-infected person with a count of 200 or fewer CD4 cells, or T-cells, per cubic millimeter of blood. This immune-system cell, which in a healthy person is found at levels of about 1,000 per cubic millimeter, is destroyed by HIV.
Dr. James W. Curran, director of the AIDS division at the CDC's Na tional Center for Infectious Diseases, said the broader definition could add 150,000 to 200,000 people to the AIDS caseload. As of June, 182,834 AIDS cases had been reported to the agency, 116,184 of which have resulted in death.
Dr. Curran said it would also detect cases of AIDS sooner.
"This allows cases to be reported at the first laboratory sign of severe immunodeficiency," he said. "That's the time when people are in severe need of medical care and services."
He also said the change would "have implications for virtually every symptom associated with HIV."
Health officials in New York City, which has the largest number of reported AIDS cases in the country, said the expanded definition would increase its caseload by 40 percent to 50 percent, adding from 14,000 to 17,000 to the current caseload of 34,393.
"What it will do is allow us to count a lot of people a year or two earlier," said Dr. Polly Thomas, director of AIDS/HIV surveillance for the New York City Health Department.
But Dr. Thomas said the new definition may not capture many indigent people and intravenous drug users who are very ill or dying, the same group most likely to have been missed by the old version of the definition, because they have not sought medical attention or lack access to it or because they often suffer from conditions not included in the current list of AIDS-defining illnesses.
Critics of the old definition said yesterday that the change was a step in the right direction but that there was still a need to add new conditions to improve diagnoses and the accuracy of the count.
Theresa M. McGovern, a New York City lawyer who represents women and current and former drug users infected with HIV, said underreporting would still occur because many doctors did not recognize conditions outside the list, such as bacterial pneumonia and cervical cancer, as being related to the virus. As a result, she said, they are not tested for AIDS in the first place.
Some officials had resisted adding to the list of conditions, saying that continuously updating the list would seriously hamper their ability to trace the epidemic.