9.2.1 Positive HIV test
The method for the HIV rapid test is described in Study Session 24 of Communicable Diseases, Part 3. Study Session 28 of that Module deals with HIV in children.
Serological (or antibody) tests (also called rapid tests) detect antibodies made by immune cells in response to the virus. They do not detect the virus itself. An HIV-infected mother produces antibodies in her blood. These antibodies from the mother can get into the baby during delivery and may stay in the child’s blood until the age of 18 months. This means that a positive antibody test in children under the age of 18 months is not reliable and does not confirm that the child is truly HIV-infected. Serological or antibody tests are used to confirm HIV infection in children who are more than 18 months of age. If a rapid antibody test is done for a child older than 18 months and the result is positive, then that child is HIV-infected.
Virological tests, such as DNA PCR tests, directly detect HIV in the blood. These tests can therefore detect HIV infection in the child before the child is 18 months old. If a DNA PCR test is done for an infant and the result is positive, then that infant is HIV-infected.
You may get a child whose initial HIV test is negative, but if you know the mother is HIV-positive and is continuing to breastfeed, you should repeat the test because HIV can be transmitted in breastmilk. The test should be repeated six weeks after breastfeeding has stopped.
As you read above, when you ask a mother about her or her child’s HIV status, it is important that you pose the question in a careful way and maintain confidentiality as much as possible since this is sensitive information.
A two-month-old baby has a positive virological test. Is the baby HIV-infected?
Yes, because virological tests detect HIV in the blood and a positive test shows the presence of HIV, whatever the age of the baby and whether or not the baby is exclusively breastfed.
A two-month-old breastfeeding baby has a positive antibody (serological) test. Is the baby HIV-infected?
It is difficult to conclude in this case because, at two months, an antibody test cannot be used to confirm HIV infection. Antibodies can pass from mother to baby and may stay in the baby’s blood for as long as 18 months.
A 20-month-old child who has stopped breastfeeding more than six weeks ago has a positive HIV antibody test. Is that child HIV-infected?
Yes, because in a child who is 18 months or older, an antibody test can confirm the diagnosis of HIV infection.
A nine-month-old breastfeeding baby has a negative virological test. Is the baby HIV-infected?
It is difficult to conclude in this case. Although the test suggests now that the baby is not infected, if he is breastfeeding from an HIV-infected mother, he may acquire the infection later. Once a child is 18 months or older, the antibody test can be repeated six weeks after stopping breastfeeding.
9.2 Testing infants and children for HIV