There are a variety of ways to test for HIV infection. Not all individuals who are HIV positive will also test positive for AIDS.

HIV tests detect one or more of the following:

• Antibodies to HIV:
• These are the most commonly used HIV tests
• Viral proteins:
• p24 antigen: used for very early detection in cases of blood contamination
• Viral nucleic acids:
• Used for very early detection in cases of blood contamination

Detecting Antibodies to HIV
The two types of HIV antibody tests are the:

• ELISA test
• Enzyme-linked immunoabsorbent assay
• Western blot

The ELISA is a screening test: it is reported as positive or negative. The ELISA test may be falsely positive in:

• Women who have had multiple pregnancies
• Those recently vaccinated against influenza or hepatitis B
• Those who have received multiple blood transfusions
• Those who have an autoimmune disease

The Western blot test is used to confirm HIV infection in someone who is ELISA positive. If the Western blot is negative (and remains so for 6 months) HIV infection is not present.

p24 Antigen Testing
HIV antigen tests detect the p24 antigen, which is a protein that is produced by the HIV virus. This test is used to:

• Help in the diagnosis of AIDS
• Monitor the response to treatment
• Early detection of HIV virus in blood donors
• Detect the presence of HIV in the blood of newborns, born to mothers who have HIV

Viral Nucleic Acid Testing
Nucleic acids are the building blocks of DNA and RNA. The HIV nucleic acid test detects the presence of HIV nucleic acids. This test is used to:

• Monitor the response to treatment
• Early detection of HIV virus in blood donors
• Detect the presence of HIV in the blood of newborns, born to mothers who have HIV