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Mothers: Since HIV–infected mothers can pass the virus to their baby during pregnancy, labor, delivery, or breastfeeding, the U.S. Centers for Disease Control and Prevention (CDC) recommends that all pregnant women get tested for HIV. The most common HIV tests use blood to detect HIV infection. In most cases the enzyme immunoassay (EIA), used on blood drawn from a vein, is used to look for antibodies to HIV. These antibodies, which are present in the blood, are created to help the body detect and fight off the virus. If HIV antibodies are present in the blood, the patient has HIV, and will receive a positive test result. This initial test must be followed–up with a confirmatory test like the Western blot to make a positive diagnosis. During a western blot test, a small sample of blood is taken, and it is used to detect HIV antibodies, not the HIV virus itself. Alternatively, a rapid test may be conducted. A rapid test produces results in about 20 minutes. Rapid tests use a sample of blood or oral fluid (fluid taken from the patient's gums) to detect HIV antibodies. The patient's sample is placed on a test strip that contains HIV antigens. If the patient has developed HIV antibodies, the strip changes colors, indicating a seropositive result. A positive HIV test should be confirmed with a follow–up confirmatory test before a final diagnosis of infection can be made. These tests have similar accuracy rates as traditional ELISA screening tests. Babies: In the United States, it is recommended that all babies born to HIV–positive mothers be tested for the virus. However, different states have different testing guidelines. Some states, like New York and Connecticut, require that babies receive a mandatory HIV test if the HIV status of their mother is unknown. Some states require that all babies be tested for HIV unless the mother refuses. Other states only require healthcare facilities to offer an HIV test to pregnant women (not their babies), which they can either accept or refuse. Prenatal tests before birth, including amniocentesis and chorionic villus sampling, should not be conducted because there is a slight risk of bleeding, which may increase the risk of transmitting the infection. HIV infection is generally difficult to diagnose in newborns and infants. Babies born to infected mothers have HIV antibodies that they received from their mothers before birth. These antibodies may be present in the blood for up to 18 months. Therefore, a standard HIV antibody test is not useful in these babies until they reach this age. Instead, tests that detect the HIV itself are performed in newborns. One laboratory procedure, known as polymerase chain reaction (PCR), can detect minute quantities of the virus in an infant's blood. Alternatively, an HIV virus culture can be performed. During the procedure, a sample of an infant's blood is placed on a Petri dish in a controlled environment that allows the virus to grow. Currently, PCR assays and HIV cultures can effectively diagnose about one–third of infants at birth who ultimately prove to be HIV–infected. This is because the infant is newly infected, and there may not be enough viral particles to detect HIV. These techniques are more effective (about 90% effective) when they are performed in infants two months of age, and about 95% effective in patients three months of age.
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