A study of more than 300 infants in Baltimore and Haiti released yesterday confirms that a simple and inexpensive blood test can identify infection with the AIDS virus in children as young as 3 to 6 months.
The new test will allow doctors and parents to determine the status of newborns much sooner than could be done using the most common blood tests for the human immunodeficiency virus that causes AIDS.
The most widely used tests cannot reliably detect HIV infection in infants younger than 12 to 15 months of age.
The chance that an HIV-infected mother will pass the virus to her fetus is estimated between 13 percent and 45 percent, according to experts.
"Any lab that does routine serologic [blood] testing for HIV can do it," says Dr. Thomas C. Quinn, a Johns Hopkins University professor and senior investigator at the National Institute of Allergy and Infectious Diseases.
"The cost is about $30, which is relatively inexpensive in comparison to the other tests available," he said.
By being able to identify HIV-infected infants earlier, physicians will be able to begin drug treatment sooner or, in the case of an infant that tests negative, choose to delay treatment that can produce severe side-effects.
"You wouldn't want to expose a healthy baby unless you could say whether the child's infected," Dr. Quinn said.
The new test also will limit the stress of parents who fear for their child's heath: "Fifteen months is an awful long time for a parent to wonder about HIV infection," said Dr. Quinn.
Through October 1991, 3,372 children have been diagnosed with AIDS in the United States and 1,798 have died. Experts estimate that between 7,000 and 10,000 additional children are currently infected with HIV nationwide.
The results of the study show that infants who test positive at three months using the new procedure are virtually certain to be infected. The diagnosis is less precise in infants who test negative at that early age: Some will not begin to manufacture antibodies to the virus until six months, and a negative result cannot be called conclusive until about nine months, according to Dr. Quinn.
The most widely used HIV tests cannot determine infection among infants because they can't distinguish between antibodies passed from mother to child and antibodies developed by the child to fight infection. Therefore, many children of infected mothers test positive for up to 15 months even though they aren't infected.
The new test detects another antibody to HIV that cannot be transmitted from mother to her fetus because it cannot pass through the placenta. As a result, a positive result on the new test confirms that the child is infected.
The joint report by Johns Hopkins and the National Institute is further corroborated by a similar study by State University of New York researchers in Brooklyn, who used the new test to track HIV infection among a group of 58 children.
Both groups reported their findings in today's edition of the Journal of the American Medical Association.
Dr. Quinn noted that while the most commonly used test for HIV is ineffective for identifying the virus in newborns, other, more expensive tests do exist and are often used at larger research hospitals in the nation.
"If the child is a patient at a research center like Hopkins or the University of Maryland, for example, there were ways for a physician to find out earlier than 15 months," Dr. Quinn explained.
The new test, however, is simple, fast and inexpensive and will therefore allow physicians at smaller community hospitals, clinics and in developing countries to identify HIV-infected children at an earlier age.