HIV Test Sensitivity: False Negative and False Positive Results
HIV testing is done by two different types of tests: screening and confirmatory. These tests are meant to be very specific for HIV. Both tests should be positive before a result is called positive for HIV.
- Screening test: The first test performed to determine for HIV status is called a “screening” test. The scientific name for this test is an ELISA. This test is purposely set to detect as many people as possible. If the ELISA test is positive, the lab usually repeats it on the same sample.
- Confirmatory test: If the second test is positive, then they do a confirmatory test. This is scientifically called a western blot or immunofluoresence assay.
There is a small chance that one or either of these tests will be falsely positive. That is, the test is positive but the person really does not have HIV. Some diseases or vaccinations (Influenza shots) can occasionally turn the test positive but then on repeat it becomes negative.
An example of this is a patient I once had that received antibodies (immunoglobulins). They had a positive result that ultimately turned out negative once retested. The best advice is for anyone with a positive test to go see a doctor qualified to test and counsel them on HIV and be retested to confirm the results.
To Learn More:
- HIV and AIDs Basics: Prevention and Risks
- HIV in Infants and Children
- Preventing Mother-to-Child Transmission of HIV
- Women and HIV
- Symptoms and Warning Signs of HIV
- Getting Tested for HIV
- Types of HIV Tests
- HIV Transmission and Oral Sex
- Transmission Risk by Sexual Interaction
- Your HIV Positive Partner and You
- Back to HIV and AIDs Overview
For more information:
Go to the HIV and AIDS health topic.