MONTREAL — The U.S. Public Health Service plans to recommend greatly expanded voluntary AIDS antibody testing to identify infected individuals, with the aim of preventing life-threatening Pneumocystis carinii pneumonia.
The new guidelines, a draft of which was made available Tuesday, are a response to growing evidence that antibody testing may help physicians improve the medical care of individuals who carry the human immunodeficiency virus, or HIV. Previously, antibody testing has been advocated primarily as a means of interrupting transmission of the deadly virus, which causes AIDS.
"Today, there are extraordinary personal, medical and public health reasons why a person should know if he or she is infected with HIV," said Dr. James O. Mason, the U.S. assistant secretary for health at the Fifth International Conference on AIDS.
The testing and treatment recommendations, under development since February, are expected to be published later this month in the public health service's Morbidity and Mortality Weekly Report, a health service official said.
If fully implemented by physicians, the guidelines may cost HIV-infected individuals and their insurers $1 billion a year or more for additional medical tests, physician visits and medications. Many infected individuals, primarily in cities with large numbers of AIDS cases, are already receiving such monitoring and treatments.
"I think we're talking about a billion dollars--but how many billions I would be fearful of trying to put a price tag on at this point in time," Mason said at a press conference.
The draft proposal urges those who have refrained from AIDS antibody testing, including gay men and intravenous drug users, to consider changing their minds.
Mason said that if he tested HIV positive, he would want periodic laboratory tests of his immune system function so that medications could be "instituted on my behalf as they become clinically useful."
Mason added: "Aside from the public health value of counseling HIV-positive individuals, it is important for personal health reasons to identify positive individuals who may have no idea that they are infected."
The Centers for Disease Control estimates that between 1 million and 1.5 million Americans are infected with HIV. But so far only about 120,000, or about 10%, have been informed of their infection status through public HIV counseling and testing centers. An unknown additional number have tested positive on AIDS antibody tests obtained through their personal physicians. There are no accurate estimates of the percentage of infected individuals who would qualify for the preventive treatments.
In February, the Food and Drug Administration authorized widespread use of the investigational drug aerosol pentamidine for the prevention of pneumocystis in HIV-infected individuals with a history of the pneumonia or for asymptomatic individuals with severely depleted counts of T-4 white blood cells. If untreated, such immune-deficient patients have about a 20% risk of developing pneumocystis within one year.
Final FDA marketing approval for prescription sales of aerosol pentamidine is expected within weeks.
The draft of the Public Health Service guidelines says that either one of two drugs--aerosol pentamidine, given once a month, and oral trimethoprim-sulfamethoxazole, given twice daily, are safe and effective in preventing pneumocystis pneumonia.
A year of monthly 300-milligram aerosol pentamidine treatments may cost $2,100 or more. By comparison, trimethoprim-sulfamethoxazole is relatively inexpensive; it can be purchased in bulk for about 10 cents per double-strength pill. Some AIDS experts believe that the risk of serious side effects, such as anemia, are significantly greater with the pills. Federally sponsored studies comparing these two treatments are in progress.
According to the draft guidelines, all people found to be HIV-infected should have a measurement of their T-4 white blood cells, a test that can cost $100 to $150. If the T-4 measurement is 200 cells per cubic millimeter or less or if the cells represent less than 20% of the total white blood cells, pneumocystis prevention should be started. For individuals with higher T-4 counts, repeat testing is recommended at least every six months.
Before the preventive treatments are started, the Public Health Service cautions physicians to make sure their patients do not already have pneumocystis or other lung diseases, according to the draft. It also advises doctors to closely follow patients for development of pneumocystis, since neither of the recommended therapies are completely protective.
In another presentation, Johns Hopkins University researchers reported that women who smoke cigarettes appear to be more likely than others to become infected with the AIDS virus. Their study of Haitian women found that smokers were nearly twice as likely as nonsmokers to be infected with the human immunodeficiency virus.