According to the Centers for Disease Control and Prevention, "Of the more than 1 million persons in the United States living with HIV/AIDS, an estimated 21 percent are unaware they are infected." Early testing of individuals who have been exposed to HIV ensures early treatment. There are three types of tests used to screen for HIV.
HIV Antibody Test
The HIV antibody test detects antibodies, which are proteins that the body produces in response to exposure to HIV. This test is accurate and inexpensive. According to AVERT, an international AIDS charity, "Most people develop detectable HIV antibodies within 6 to 12 weeks of infection. In very rare cases, it can take up to six months."
The HIV antibody test is administered three months after exposure to the virus. However, the ELISA or enzyme-linked immunoabsorbent antibody test is highly sensitive and can detect other antibodies, too, which can result in false-positive test results. All positive ELISA results are confirmed by additional testing. A rapid HIV test is a HIV antibody test that is done by the individual without the need for laboratory analysis. A person takes a sample of saliva or blood by pricking a finger and is able to get results within 20 minutes. Positive results are confirmed with a HIV antibody test performed in a clinic, physician's office or hospital laboratory.
P24 Antigen Test
An antigen is a substance that causes the immune system to produce antibodies. The protein P24 is the antigen that produces antibodies following exposure to HIV P24 and is produced in large amounts during the early phase of infection and decreases to undetectable levels once the infection progresses. This type of testing has a low sensitivity rate and is effective immediately after exposure to HIV. Combining the technology of P24 and antibody tests has produced an accurate test for detecting HIV. This hybrid test is called fourth-generation testing.
PCR Test
The PCR or Polymerase Chain Reaction test screens for HIV by identifying the genetic components of the virus found in the blood sample. HIV genetic material is detected within two to three weeks of exposure.
This test is used on newborns of HIV-infected mothers. A baby receives antibodies from its mother during pregnancy and breastfeeding; a HIV positive mother will also pass her HIV antibodies on to her unborn child. Uninfected babies lose the maternal HIV antibodies by the age of 18 months. The PCR test can detect if the baby is infected by the age of three months. The PCR test is used to screen blood supplies for HIV.
